Double Skin Glass Facades: A Thesis Project by Open Atelier Architects

DOUBLE â&#x2014;? SKIN GLASS FACADES For High Performance Buildings

Anthony M. Catsimatides

Double ● Skin Glass Façades For High Performance Buildings By Anthony M. Catsimatides, AIA May 2, 2007

Abstract Double Skin Glass Façades are an emerging aspect of high-performance building envelope systems. This thesis documents an architectural investigation of the building science and design of this type of envelope as a measure of sustainable energy efficient and green design practices. Ventilation modes and types of double skin glass façades in use today are identified and analyzed for thermal and wind, or air flow, strategies. Natural ventilation with used as a means of reducing dependence on mechanical equipment. Passive solar and air flow design principles are used for evaluating the performance of double skin glass façades. The thesis stems from my belief that the building industry today needs to look towards more energy-efficient building methods in keeping with sustainable building design practices. The research is a contribution to the practice of maximizing indoor comfort for building occupants’ health and well being, while minimizing dependence on costly and limited non-renewable geological resources, such as fossil fuels. In order for the human race to continue indefinitely, our environmental impact must be less than or equal to the impact level that the earth can sustain1. This is a principle of sustainable design and can be used to account for the management of natural resources and energy consumption2. Energy from natural occurring renewable sources is free and preferable, the prime sources being sun and wind.

1 Terry Williamson, Antony Radford & Helen Bennetts in Understanding Sustainable Architecture attribute this concept to Richard Sylvan and David Bennett whose 1995 book, The Greening of Ethics: From Anthropocentrism to Deep Green Theory, devise an equation of human impact on environmental conditions in the form EI = P X C X T, (Environmental Impact of a group = Population X Consumption X Technology). 2 In The Philosophy of Sustainable Design, Jason McLennan lists this as one of the six governing principles of Sustainable Design, Ecotone LLC, 2004, p. 38

Double Skin Glass Façades

Double Skin Glass Faรงades

Double ● Skin Glass Façades For High Performance Buildings

SYRACUSE UNIVERSITY School of Architecture M. Arch II Research Program

By Anthony M. Catsimatides, AIA Bachelor of Architecture, Pratt Institute, 1984

May 2, 2007 Professor Timothy Stenson, School of Architecture, Advisor Professors Terrance Goode, Ted Brown, School of Architecture, Advisory Panel Mark Linder, Graduate Architecture Department Chair/Associate Professor Mark Bomberg, Mechanical & Aerospace Engineering, Building Sciences Advisor

Double Skin Glass Façades

iii

All diagrams, illustrations and drawings are by the author unless otherwise noted.

Double Skin Glass FaĂ§ades

Table of Contents

Preface ............................................................................................................................................ 1 PART 1: Introduction ....................................................................................................................... 3 Double Skin Glass Façades: An Early Example ............................................................................. 3 Mechanization Took Command .................................................................................................. 4 A Brief History of Glass used in Architecture .............................................................................. 4 Use of Architectural Glass since the 19th Century ..................................................................... 5 On Sustainable Design ............................................................................................................... 7 PART 2: Double Skin Glass Façades ........................................................................................... 10 Defining the Double Skin Glass Façade........................................................................................ 10 Double Skin Glass Façade Principles ........................................................................................... 12 Modes........................................................................................................................................ 12 Ventilation Types....................................................................................................................... 14 Partitioning Types...................................................................................................................... 15 Strategies....................................................................................................................................... 17 Planning......................................................................................................................................... 22 Double Skin Glass Façades in High Rise Design ..................................................................... 22 Selection Process...................................................................................................................... 23 Re-Skinning............................................................................................................................... 24 PART 3: Program and Performance.............................................................................................. 25 Project Design & Strategy ............................................................................................................. 25 Building Form & Aerophysics .................................................................................................... 25 Skin Shape Diagramming ......................................................................................................... 28 Project Design & Planning ........................................................................................................ 31 Basic Double Skin Glass Façade Envelope.............................................................................. 32 Tower Scheme .......................................................................................................................... 36 Faceted Surface Texture........................................................................................................... 41 Curved Surface Texture ............................................................................................................ 46 Performance Criteria for Evaluation .............................................................................................. 51 Analysis ..................................................................................................................................... 52 Test Case Parameters .............................................................................................................. 53 CFD Test Set up........................................................................................................................ 53 Pros & Cons of cavity widths..................................................................................................... 54 PART 4: Net Present Value Modeling ........................................................................................... 56 PART 5: Conclusions .................................................................................................................... 74 US Market Acceptance ............................................................................................................. 74

Double Skin Glass Façades

Appendix A: Case Studies............................................................................................................. 78 Appendix B: Survey ....................................................................................................................... 87 Bibliography & Reference.............................................................................................................. 90 Biographical Data .......................................................................................................................... 93

Double Skin Glass Faรงades

List of Illustrations

Figures 1 & 2 City de Refuge, Le Corbusier, 1930, credits Oeuvre Complete 1929-1934 & Fondation Le Corbusier .... 3 Figure 3 Centrosoyuz, Le Corbusier, 1929 – 1930, photo credit Oeuvre Complete 1910-1929 ....................................... 3 Figure 4 Seattle Justice Center by NBBJ, photo credit NBBJ........................................................................................... 4 Figures 5 & 6 Commerzbank by Norman Foster, credits, Norman Foster Works 4, edited by David Jenkins................ 10 Figure 7 Double Skin Glass Façade Section ................................................................................................................... 11 Figure 8 Corridor type multi story façade ....................................................................................................................... 11 Figure 9 Double Skin Glass Façade Modes .................................................................................................................... 12 Figure 10 Occidental Chemical, Photo credit Cannon Design ........................................................................................ 12 Figure 11 Melvin J. and Claire Levine Hall, University of Pennsylvania School of Engineering & Applied Science, Kieren Timberlake Architects, 2006, credit, Kieren Timberlake Architects .......................................................... 13 Figure 12 Double Skin Glass Façade Ventilation Types................................................................................................. 14 Figure 13 Shaft Box Strategy Figure 14 Boxed Window Strategy ............................................................................. 15 Figures 15 Single Story Strategy Figure 16 Multi Story Strategy............................................................................... 16 Figure 17 Thermal performance diagram........................................................................................................................ 17 Figure 18 Air pressure difference in cavity, drawn by the author, adopted from Double-Skin Façades, Integrated Planning by Oesterle .............................................................................................................................................. 18 Figure 19 Natural Ventilation diagram ........................................................................................................................... 19 Figure 20 Stadttor, Photo Credit, Petzinka Pink & Partners ........................................................................................... 20 Figure 21 Natural Daylight diagram ............................................................................................................................... 20 Figure 22 Typical cavity corridor schemes ..................................................................................................................... 21 Figure 23 Re-skinning Existing Buildings ...................................................................................................................... 24 Figure 24 Plan & Elevation building shapes ................................................................................................................... 25 Figure 25 Volumes for Building shapes.......................................................................................................................... 26 Figure 26 Wind Flow Modeling...................................................................................................................................... 26 Figure 27 Air Flow modeling about a curved form......................................................................................................... 27 Figure 28 Air flow patterns............................................................................................................................................. 27 Figure 29 Cavity Plan & Section diagrams ..................................................................................................................... 28 Figure 30 Volumetric lofted & extruded shapes ............................................................................................................. 29 Figure 31 Volumetric lofted & extruded compound shapes............................................................................................ 29 Figure 32 Lofted forms with ports .................................................................................................................................. 30 Figure 33 Sun Path & Wind Rose diagrams.................................................................................................................... 31 Figure 34 Analysis of air flow ........................................................................................................................................ 32 Figure 35 Double Skin Glass Façade Section diagram ................................................................................................... 32 Figure 36 Model Envelope with louvered vents.............................................................................................................. 33 Figure 37 Modular Façade Elevation .............................................................................................................................. 33 Figure 38 Building & Site Plan....................................................................................................................................... 34 Figure 39 Typical Tower Floor Plan............................................................................................................................... 35 Figure 40 Performance Design Criteria .......................................................................................................................... 36 Figure 41 Perspective view of building with faceted skin............................................................................................... 37 Figure 42 Site shadow studies......................................................................................................................................... 38 Figure 43 Cross Section of tower with Wind Strategy.................................................................................................... 38 Figure 44 Year round mode daylight strategy................................................................................................................. 39 Figure 45 Heat recovery strategy – Winter Operation .................................................................................................... 39 Figure 46 Ventilation strategy – Summer Operation ...................................................................................................... 39 Figure 47 Standardized detail for double skin glass facade ............................................................................................ 40 Figure 48 Rough surface texture cavity shape ................................................................................................................ 41 Figure 49 Faceted Form Module..................................................................................................................................... 41 Figure 50 Single Bay Modules........................................................................................................................................ 41

Double Skin Glass Façades

vii

Figure 51 Cavity thermal distribution ............................................................................................................................. 42 Figure 52 Faceted wall.................................................................................................................................................... 43 Figure 53 Faceted Skin Section ...................................................................................................................................... 44 Figure 54 Building Elevations for faceted surface texture scheme ................................................................................. 45 Figure 55 Wavy or curved surface texture cavity scheme............................................................................................... 46 Figure 56 Wavy or curved formed surface with contoured vents.................................................................................... 46 Figure 57 Habitable environment within vented cavity .................................................................................................. 47 Figure 58Air flow prediction w/ contoured vents Figure 59 Venting the Skin ........................................................... 47 Figure 60 Wavy or contoured curve formed surface with ports ...................................................................................... 48 Figure 61 Habitable environment within ported cavity................................................................................................... 49 Figure 62 Air flow and thermal prediction w/ contoured ports Figure 63 Venting the skin using a port.................... 49 Figure 64 Building Elevations with contoured wavy port surface texture scheme.......................................................... 50 Figure 65 Strategy Technology Matrix ........................................................................................................................... 50 Figure 66 Performance Considerations diagram ............................................................................................................. 51 Figure 67 Building Floor Plan for NPV modeling .......................................................................................................... 57 Figure 68 Building Elevation for NPV modeling............................................................................................................ 57 Figure 69 GSW West Faรงade Detail ............................................................................................................................... 78 Figure 70 GSW Plan ....................................................................................................................................................... 79 Figure 71 GSW Elevation............................................................................................................................................... 80 Figure 72 GSW Tower Cross Section ............................................................................................................................. 80 Figure 73 GSW Diagrammatic studies............................................................................................................................ 80 Figure 74 GSW Building Section ................................................................................................................................... 81 Figure 75 Levine Hall Massing....................................................................................................................................... 82 Figure 76 Levine Hall curtain wall concept section ........................................................................................................ 82 Figure 77 Levine Hall curtain wall detail section ........................................................................................................... 83 Figure 78 Levine Hall winter mode operation ................................................................................................................ 83 Figure 79 Levine Hall summer mode operation.............................................................................................................. 83 Figure 80 CoE, Energy Strategies................................................................................................................................... 84 Figure 81 CoE, Exhaust Strategy .................................................................................................................................... 84 Figure 82 CoE, South-East Elevation ............................................................................................................................. 85 Figure 83 CoE Floor Plan ............................................................................................................................................... 85 Figure 84 CoE Double Skin Glass Faรงade Detail ........................................................................................................... 85 Figure 85 CoE, Winter - Summer Ventilation Strategies................................................................................................ 86 Figure 86 Survey of Ventilation Modes.......................................................................................................................... 87 Figure 87 European Map ................................................................................................................................................ 88 Figure 88 US & Canada Map.......................................................................................................................................... 89

viii

Double Skin Glass Faรงades

Double Skin Glass Façades

Preface The thesis is divided into 5 parts, each pertaining to different aspects of double skin glass façades. Part 1 describes an early attempt at designing with double skin glass façades. It is also a brief introduction of the history of glass and glazing. This is included because of my interest in historic reference and my curiosity on how ideas begin and take root over time. I also include a short discussion on sustainable design and why I believe double skin glass façades are relevant in today’s energy debate. Part 2 investigates double skin glass façades as to what they are and how they work. It also categorizes double skin glass façades by modes, ventilation types and partition types. Part 3 is a project and approach using double skin glass façade prototyping. It establishes a process for performance criteria and evaluation and sets up the framework for using computational fluid dynamic (CFD) modeling. Actual CFD testing was not conducted as part of this research, but it is the author’s intention to pursue this process later, therefore the framework describes the criteria and set up for future testing. This part also includes planning and application strategies for double skin glass façades. Part 4 is an exercise comparing double skin glass façade initial costs with potential long-term energy savings as compared to a standard curtain wall using a simple Net Present Value method. Part 5 concludes with some broad topics. Although this part is not a deep investigation, I believe that it will be necessary at some point to address the issues raised if double skin glass façades are to be considered viable building solutions in the United States. Appendix A includes three case studies, each exhibiting a unique quality of double skin glass façades. Finally, Appendix B shows the results of a building survey I conducted within the United States, Canada and Europe, to determine how many buildings I could find that use double skin glass façades, and where they are located.

Acknowledgements I would like to express my fondest appreciation and affection for my wife, Alyson Markell, without whose patience and support, this crazy mid career back to school dream would not have been possible. I wish to thank Tim Stenson whose persistence and focus helped to keep me on track. In addition, a special thank you to Mark Linder who supported me in my enthusiasm for sustainable architecture. The invaluable words of encouragement and comments by Terrance Goode and Ted Brown were without a doubt instrumental in the direction my thesis took, thank you. I would also like to acknowledge Dr. Mark Bomberg of the School of Engineering for invaluable depth and insight and a great sense of humor.

Double Skin Glass Façades

Double Skin Glass Faรงades

PART 1: Introduction Double Skin Glass Façades: An Early Example In 1930, Le Corbusier proposed two concepts in building envelope technology that coincided with the beginning of mechanical air conditioning systems. He proposed a ‘double glass skin’ with “la respiration exacte”, a carefully controlled mechanical ventilation system, and “le mur neutralisant”, an invention to maintain an interior comfort temperature of 18°C by introducing a cooling system in hot climates and a heating system in cold climates within the cavity of a double walled glass façade. The multi layered glass façade concept with a mechanically assisted environmental control was first proposed for Centrosoyuz in Moscow by Le Corbusier around 1930, and then was to be employed in the Cite de Refuge in Paris, France. Unfortunately, budget cuts prevented Le Corbusier from realizing the full potential of an integrated mechanically assisted cavity to control interior occupant comfort in either of these projects. Nevertheless, the French glass manufacturer, St Gobain, in 1931, conducted laboratory tests of the system, and concluded that a third glass skin trapping still air would be required to make the system viable.

Figures 1 & 2 City de Refuge, Le Corbusier, 1930, credits Oeuvre Complete 1929-1934 & Fondation Le Corbusier The glass façade was intended as a double walled enclosure with mechanically assisted ventilation within the cavity. Le Corbusier was always quick to jump on the latest technology.

Today a similar system, known as a buffer zone, has been successfully used in recent years throughout several areas of the northern Europe.1

Figure 3 Centrosoyuz, Le Corbusier, 1929 – 1930, photo credit Oeuvre Complete 1910-1929

Double Skin Glass Façades

Mechanization Took Command Over the course of the 20th century, mechanization of buildings began to dominate our environment. The industrialization and mechanization of building designs shifted the focus of building systems away from age’s old practice of working with renewable natural resources, such as solar and wind energy, and towards finite natural resources, such as fossil fuels. By 1969 Reyner Banham in, “The Architecture of the WellTempered Environment”, was prodding architects to take notice of the practice of relying solely on energy powered mechanical technology for conditioning large buildings. He created a quiet stir by raising awareness of how wasteful and ill designed the methods of integrating mechanical building systems were, blaming the demise of technological application on the separation of the professions of engineering and architecture.2 This is perhaps one of the earliest attempts in 20th century western culture to motivate architects to be more environmentally responsive stewards, while keeping technology in the forefront. By the mid 1970’s, when the energy crises forced us to take notice, most glass skyscrapers in New York and other cities relying solely on mechanical conditioning systems had already been built. It would take another 20 years and another threat of energy price hikes for the idea of high performance buildings to be seriously considered a necessary alternative to wasteful fossil fuel consuming buildings. Although high performance buildings and energy efficient building design have not been the norm in building practice, it is on the rise as can be evidenced in the many new recent buildings that vie for LEED Certification. One recently completed example in the United States undertaken with sustainable design practices is the Seattle Justice Center by NBBJ that includes a green roof, double skin glass façade, energy efficient variable air volume fans and individual air handling systems for each floor.

Figure 4 Seattle Justice Center by NBBJ, photo credit NBBJ Double skin glass façade is only part of a list of other energy efficient solutions, completed 2002

A Brief History of Glass used in Architecture In the early days of its manufacturing for building technology, glass was employed within a solid wall opening in order to allow light to penetrate to the interior of the building. Through newly developed techniques of annealing, along with the inventions of the sheet-roll process and tempering of glass, the wall opening enlarged, eventually leading to the entire façade as glass. In this fashion, the solid building skin of stone, wood, or stucco gave way to the entire wall as transparency inherent in glazing material. Historically, glass has been used to light interior spaces during daytime hours and as a shield against external weather forces. Ancient agrarian societies organized most of their social activities outdoors,

Double Skin Glass Façades

reducing the need for being indoors during the day. Walls were designed for protection against unfavorable environmental conditions such as rain and wind, but small wall openings were introduced for small amounts of daylight. Since indoor daylight was not a key necessity, glass was not originally used for window openings, as we know them today, but was primarily used for objects of ornament or food storage. The technological knowledge for making glass dates back to the 5th Century BC in Mesopotamia and the 4th Century BC in Egypt. It is believed that glass one to two inches thick was used in Pompeii around the 1st Century AD. It was not until 1141 AD and the work of Abbott Suger at the chapel at Saint Denis that glass was employed to play a major role in building construction3. In Abbott Suger’s design of the first Gothic cathedral, Romanesque vaults were fused into diagonal ribs that carried down through shafts and piers, which were anchored down by flying buttresses. This system allowed the reduction of wall mass to multi-tiered piers and arches with great expanses between for infill material. For this, Suger employed colored glass on a large scale as infill tracery windows between peristyle columns surrounding the sanctuary. The effect was the perception of “divine light” achieved through the colored glass.4 Between the 15th and 17th Centuries, Venice capitalized on the production of glass objects and trinkets, primarily exported to other parts of Europe. Glass gained a wide spread popularity from the 17th Century onward when in 1688 a Frenchman by the name of Bernard Perrot developed the cast glass process. Up until that time, the only methods used for glass production were the blown cylinder sheet and the crown glass process, methods that dated back almost 4000 years.

Use of Architectural Glass since the 19th Century An early modern glass building that used glass and metal structure framework innovatively was Sir Joseph Paxton’s Crystal Palace for the Great Exposition of 1851 in Hyde Park, London. This building exhibited a testament to Paxton’s ingenuity in mass production, tooling and efficiency of construction in skeletal framed enclosures with glass infill panels. The building was designed and erected in record time, but more importantly, it was designed to be recycled within a year after the exposition closed. All the steel frame members and glass were reusable in other applications, as was the case for much of the structure. The process for making glass windows at this time, known as Crown and Cylinder, was still by hand and far from perfect. Glass tubes, or cylinders, up to four feet in diameter and six feet long were produced using a traditional glass blowing technique. The cylinders were cooled, reheated and cut lengthwise then flattened. This limited the size of glass panes due to the unevenness and imperfections present in the glass cylinders. It was not until the early twentieth century that experiments in steel grid structures lead to the next evolutionary steps in glass façades. Building a skeletal frame grid allowed for the infill system of panels, traditionally stone or other solid material, to be replaced with a total glass skin, the curtain wall. In 1918, the Hallidie Building in San Francisco by Willis Jefferson Polk, now home to the AIA San Francisco Chapter, was the first office building in America to employee the curtain wall. In 1921, an Office Building Project proposed for Friedrichstrasse, Berlin by Mies van de Rohe explored concepts of transparent façade technology for high-rise buildings. Great leaps in technology occurred throughout the 1900’s when through a series of developments glass manufacturers advanced the process through glass-melt sheets. In 1901, Emile Fourcault succeeded in designing a machine that would draw glass-melt upwards, vertically, through slits as it was cooled. This process however left undulations across the sheets. By 1909, Edouard Benedictus invented laminated glass by sandwiching a thin plastic film between two sheets of glass. This provided a feature of safety, unknown before. Laminated glass was first used in automobile windshields as a safety feature. In 1929, Achille Verlay, who worked for St. Gobain, developed the technique of tempering glass. The glass was hung in ovens to a certain temperature. The glass was then quickly removed and jets of cold air were blasted

Double Skin Glass Façades

uniformly on both sides of the glass creating a compressed external surface. Finally, the use of rollers that marred the surface of glass in Fourcault’s process was supplanted in 1959 by Alastair Pilkington in his float-glass process. In this process, glass was melted over a pool of liquid, such as liquefied tin, and smoothed by gravity and surface tension. Without rollers squeezing and marring the surface, grinding and polishing were no longer necessary. This process is still in use today. During the 1950’s and 1960’s throughout much of North America, particularly along the northeastern seaboard, and specifically in New York City, glass tower boxes dominated the landscape as corporate expectations seized on the glazed skins as the image of progress. At that time, the curtain wall was seen as the image of cutting edge technology for building envelopes. However, the hermetically sealed enclosures produced by these gigantic buildings required massive conditioning systems that fell out of favor during the energy crises of the 1970’s, as global oil prices spiked. A daring and innovative achievement was devised by Norman Foster, Foster and Partners, for the Willis, Faber and Dumas office building in Ipswich, England in 1971-75. He demonstrated that glass exhibits remarkable structural characteristics when he suspended glass panels from pins mounted on structural slabs above the glass. Not only was this an advanced structural detail for its time, but the building as a whole exhibited a remarkable understanding of how environmental forces reacted with a building to create an early example of ecological building design. These examples and countless others serve to inform our understanding of the potential of glass in architecture. Over the years, thermal control has been achieved with the introduction of double pane glazed window technology. Every home built today uses this technology. Two sheets of glass are held apart by a small spacer, which often includes a desiccant to control moisture, and sealed for air tightness. The air between the panes provides a buffer zone between external climates and interior conditions. For even better performance, the cavity can be filled with gasses such as argon, which has greater thermal resistance properties than air. Where UV light is a concern, coatings such as Low-E film are applied to glass surfaces. This also helps to reduce solar heat gain within the building further. As for sound control, building built near airports, for example, use triple pane glazed windows that cut decibel levels dramatically. The principle by which air between glass panes is used for separating climate conditions is one of the main principles found in double skin glass façades and will be discussed at length as part of this thesis. As technology advances, and our understanding of glass increases, we are able to use glass to control thermal, light and noise far more effectively than was previous possible. These are but a few of the advancements and benefits of glass technology in use today. As this thesis is on double skin glass façades, the background information was provided solely as a brief and general introduction to glass and glass building envelope technology.

Double Skin Glass Façades

On Sustainable Design This research was undertaken out of respect for our environment. A facet of sustainable architecture is the understanding of natural environmental processes to determine building methodologies that minimize impact on the earth’s non renewable resources. As mentioned earlier, in order for the human race to continue indefinitely, our environmental impact must be less than or equal to the impact level that the world can sustain.

Shelter From the earliest cave dwellers decorating their caves with forms mimicking natural occurrences, painting of the landscape, the animals or the act of the hunt for survival, to today’s complex interconnected social systems and patterns, there has been one thread that defines our purpose for building, and that is the urge to survive. Without some form of shelter, the process of survival is almost impossible given the extreme weather patterns of the earth’s climate. This is a significant paradigm vested as a meaningful dialogue between man and nature throughout human existence. We can define this particular human and social interaction with the natural environment as the sum of a culture’s, civilization’s, or society’s practical knowledge and skill, our technology. Beyond the basic instinct for survival, it can be argued that humans strive for comfort and enjoyment of our built and natural surrounding as well, with emphasis on beautiful or harmonious integration with nature. By studying numerous cultures through the ages, it can be seen that art and design has played an interrelated role in the manipulation of setting to attain comfort. For example, dating as far back as the Ancient Greek Temple and the many interpretations of the Asian Pagodas, to modern day museum design and the thousands of home styles, buildings as a decorated form of art are a pursue of an aesthetic ideal that has left behind an untold number of exquisite achievements. However, the social and individual emotional response to the survival instinct is what drives us to build basic shelters. Whether it is building a house to live in, a school to learn in, a church to worship in, an office to work in, or a hut to stay dry in, the instinct to building begins with the emotional vested interest of survival and self-preservation. This can be shown to be true on different levels and based on different types of buildings in different localities. Where the natural climate is more suitable for human habitation, less building materials are required for construction, such as in climates nearer the equator where simpler huts of thatch are adequate. Where climates become less favorable for human habitation, as in far northern regions approaching latitudes 35 and above, more care needs to be taken with the type of materials selected for construction and the methodologies for construction of those buildings. Typically, more building materials tend to be employed. This can be shown by the amount of insulative material used such as specialized window technology for thermal performance. Therefore, it seems at odds that for the past one hundred and fifty years, or roughly since the earliest days of the great Industrial Revolution, societies have modified the natural world in such ways leaving damaged scars on the earth and devastating consequences to fragile ecosystems. Our rivers, streams and waterways have been polluted and over harvested, our landscapes have been pillaged for natural resources such as trees for lumber or coal and oil for energy, and our air has been plagued by an overwhelming amount of carbon dioxide, puncturing a hole in our ozone layer that allows damaging ultra violet radiation to pass through. I believe we have come to a cross roads in relation to our building and design methodologies. Debates in congress and other governmental levels acknowledge scientific predictions of a global warming and excessive pollution. Visionaries like William McDonough strive to find ways to rethink the way we build and make things in order to minimize our impact on natural non renewable resources. Our existence, as we know it on earth will have to change or cease to exist5.

Double Skin Glass Façades

History is rife with cultures that have been decimated due to land use mismanagement. Without the knowledge of the ages, there is a consequence of repeating the failures of the past. Learning from the past means repeating what is relevant and natural to our instinct for survival. Ignoring the past runs counter intuitive to our primary goal and objective as stated earlier, survival. “To the contrary, depending on the strength of its philosophy (or relative fear of nature’s revenge), each past civilization seems to have risen and fallen based on its capacity to achieve a balance with nature. It is a history without logical chronology or rational structure. The only consistent pattern seems to be based on the fact that the most exploitive cultures usually committed some form of environmental suicide”6.

Durability The principle of durability of our built environment emphasizes the underlying theme of the sustainable practice of economy of our natural resources. The durability principle pertaining to buildings, takes into consideration a building’s material ability to last a very long time. Compare most buildings being built today with a 13th century Italian towns still in use. The spaces within those buildings proved flexible enough to accommodate changing needs for the past 600 years. Buildings from the time of the Industrial Revolution should be thought of in this was and not just in terms of lasting a few generations. In the recent past, mechanically dependent technological advancements made in building science manifested since the Industrial Revolution have been given priority over more passive solutions. The consequences of much of our Industrial Revolution technology had been made clear. If any of these words ring true, then our choice is limited to heed the signs of a limited natural resource planet and begin the process of efficiency and economy of material. A re-evaluation of how we make things so there is no waste as we have known in the past seems logical. The time is now for a building revolution that is taking place.

Respecting the Limitations of our Natural Resources The rising cost of fossil fuels and the externality costs they are associated with, such as pollutants and dependence on a finite resource, leads to the logical assumption that we need to reduce our dependence on fossil fuels and natural resources7 by finding alternative sources of energy and managing the remaining resources more closely. Externality cost is defined as environmental damage that results from the way something is produced but is not taken into account in establishing the market price of the goods or materials concerned. The United States, along with other countries that are increasingly growing dependent on natural resources, need to develop more efficient use of energy, and develop technologies that will allow us to reduce this dependency. Depending on sources researched, buildings in the US constitute approximately forty percent of natural resource energy consumption8. This has lead to an increasing interest in a more intelligent approach to design and energy efficient buildings. Population growth, ozone depletion, global warming, and globalization of our economies have spawned new and profound ways of thinking about our built environment. Solar capital savings are being depleted by approximately 10,000 years of stored carbon based energy, oil, coal and natural gas, per year. Between the years 1800 and 2006, the total human population has grown from one billion to just over six billion9. At this rate, we cannot continue to build without more efficient and improved resource management. In Europe, primarily Germany, Switzerland, France and England, higher fossil fuel energy costs and stricter government regulations have forced many architects to design smarter. The growing interest in energy efficient buildings has lead to the development of many innovative solutions. One particular solution is the double skin glass façade, which in one sense is a reaction to reducing dependence on fossil fuels and nonrenewable natural resources. To compound matters worse, as the cost of building material continue to rise,

Double Skin Glass Façades

in part due to increased oil prices which affect material transportation, developers still demand cheaper, faster and better solutions from the architect. Sustainable and energy efficient design solutions are becoming a necessary fact of our built environment. Double skin glass façades are but a single solution that when integrated with energy efficient mechanical systems, passive solar building designs, daylighting and indoor air-quality management strategies can address the limited resource issues.

Increasing Energy Costs The rapidly growing interest in high performance buildings due in most part to increased energy costs has necessitated new approaches to thinking about buildings. The cost of running a building is spiraling upwards at an ever-increasing rate, in large part due to worldwide events that put ever-greater demands on the cost of fossil fuels; this includes political interactions among countries as well as the depletion of our solar capital savings, i.e. oil, natural gas and coal. Addressing these concerns, architectural thinking must address cost effective solutions for running and managing more energy efficient buildings. Recently, double skin glass facades have been used in the European high performance building market, and somewhat less popularly in the US market, in as part of sustainable building practices and as a means of controlling building life cycle energy costs. As already mentioned, this type of thinking is in support of sustainable development principles. Key aspects in high performance building design require understanding of materials, processes, operability, reliability and maintainability of all aspects of design.

Healthy Buildings, Healthy Business For businesses to continue to thrive in an ever-increasing competitive market, the cost of doing business requires controlling mechanisms in every aspect of the business, including in capital building and maintenance expenses. For business models to succeed, strategic alternatives need to consider lower energy costs, higher worker productivity, healthier profit margins, increased building valuations, and decreased vacancies. Summed up, productivity is affected by improved ‘occupant health and comfort’, which can be compared with healthy and productive building occupant workdays: the healthier the building, the more productive the occupants. Double skin glass façade buildings have the advantage of natural ventilation potential as a strategy, which is one of the tenets of healthy buildings that lead to higher occupant productivity. 10

Double Skin Glass Façades

PART 2: Double Skin Glass Façades Defining the Double Skin Glass Façade A double skin glass façade can be understood as similar to a standard glass curtain wall, the difference being that a second curtain wall skin is built within proximity of the first one, anywhere from a few inches apart to several feet. The cavity created can serve as a buffer zone between the interior and exterior environment. In some cases, where the cavity is very deep, it can also serve as a functional or recreational space, such as a balcony. The Commerzbank by Norman Foster in Berlin is an example of a building designed with a double skin glass façade exterior envelope, but it also incorporates a central atrium abutting offices and multi-story gardens that, in effect, serve as public useable space within the cavity of what can loosely be defined as a double skin glass façade.

Figures 5 & 6 Commerzbank by Norman Foster, credits, Norman Foster Works 4, edited by David Jenkins Atrium of the Commerzbank showing sky gardens, above. The exterior skin of the building is designed with a double skin glass façade as shown on right. Expanding the meaning and role of the double skin glass façade, the sky gardens can be thought of as the interstitial space of an even larger width cavity.

Heat build up in the interstitial space of the double skin glass façade requires attention. Accumulated heat can be controlled either by natural ventilation means through carefully placed operable or fixed vents in the outer or inner skin, or controlled by mechanical air handling equipment or combination of both. Typically, the interior glazed curtain wall is a standard double pane glazed system. Often, operable windows are incorporated within this interior wall to allow natural ventilation into the building. As in standard window construction, the double pane glass can be filled with argon gas or include Low-E coating. The exterior curtain wall is typically single pane glazing, most often times with fixed non-operable glass panels. In some instances, the exterior glass panels are operable, an extreme example being that of a louvered curtain wall system. If glass panels are fixed, integrated venting needs to be considered or at least investigated for the cavity as heat build up within the cavity may not always be desirable.

Double Skin Glass Façades

Figure 7 Double Skin Glass Façade Section The idea of the building skin can expand to include a habitable space. The cavity may be wide enough for a person to maneuver around inside.

As will be discussed later on, several key features in combination with one another constitute different ventilation types and operating modes of double skin glass façades. Careful consideration should be given to the way in which naturally occurring forces, such as solar heat gain and air flow, play a role in governing their efficiency and performance. Before I discuss performance evaluation though, describing the functionality and make up of double skin glass façades will help to clarify exactly what double skin glass façades are and how they can be made to work to maintain indoor comfort levels.

Figure 8 Corridor type multi story façade Even a narrow interstitial space requires at least an access panel for routine maintenance.

Double Skin Glass Façades

Double Skin Glass Façade Principles In order to better define what double skin glass façades are and how they work, a categorization into modes and types was determined through investigative analysis, building survey and case study exercises. The categories, as I have defined them, fall under five modes, four partition types, and three ventilation types. I first start by categorizing the modes.

Modes Double skin glass façades can be categorized into five basic operating modes; outdoor air curtain, indoor air curtain, air supply, air exhaust and buffer zone. These modes are based mainly on how air flows into or out of the cavity, otherwise known as the interstitial space. Within these modes, there are variations that can be implemented, such as naturally or mechanically controlled cavity, and single floor or multi story cavity partitioning, which I categorize later on. Each mode and type combination is best suited depending on the application.

Figure 9 Double Skin Glass Façade Modes The five basic modes are illustrated to show how venting in combination with air flow are used for the categorization.

Closed System: Buffer Zone A buffer zone can be thought of as a plenum or space that serves as a barrier between inside and outside environments. Although I have categorized the buffer zone as one of the five modes, it is worth noting that at times, and depending on the design, any of the other four modes can be classified as buffer zones. The buffer zone mode, therefore, is integral to the other modes. In the buffer zone design, air does not enter or exit from the cavity. Figure 9 shows the basic principle of the buffer zone. An example of the buffer zone is the Occidental Chemical Building in Niagara, New York built in 1980. During the winter months, external vents are closed allowing for a thermal action within the cavity to buffer the interior space from the exterior environment. During summer months, vents at the external most skin are open, alleviating heat build up within the cavity. As a result interior temperature conditions are moderated.

Figure 10 Occidental Chemical, Photo credit Cannon Design This building is the first design in the United States built using the double skin glass façade. The skin is symmetrical on all four sides. A more efficient use of double skin glass façades is to use it only where it can be more effective, in that part of the country, typically it is the south or west walls.

Double Skin Glass Façades

Open System: Exhaust and Supply Exhaust mode façades diffuse air from within a building to the external environment while the supply mode draws air from the environment to the interior of the building. Figure 9 also shows the basic principles of air supply and air exhaust mode façades. An example of the use of the cavity as an exhaust plenum is Levin Hall at the University of Pennsylvania, completed in 2006 by Kieren Timberlake Architects. The exterior skin is used in a traditional exhaust duct manner to carry spent air into round ducts, which in turn carry the air through a vertical shaft to the mechanical room above. In order for air to be continuously cycled through the narrow cavity, operable windows on the internal skin are not sealed with rubber gaskets as in a conventional window, but have instead bristles that maintain an open crease at all times even as the window is closed. Air movement is controlled through dampers in the ductwork. See Appendix A for a case study of this building.

Figure 11 Melvin J. and Claire Levine Hall, University of Pennsylvania School of Engineering & Applied Science, Kieren Timberlake Architects, 2006, credit, Kieren Timberlake Architects The exterior double glazed façade has roughly a 6”cavity connected to the return ducting system and used as a supplemental return air plenum for the building,

Outdoor and Indoor Air Curtain Much like the exhaust and supply modes, outdoor and indoor air curtain modes allow for the circulation of air within the cavity. In an outdoor air curtain, design outside air is circulated through the cavity and exhausted back to the outside. The indoor air curtain design works along similar principles, only the air is circulated and retained within the building’s enclosure. Often times mechanically assisted means provide the catalyst for moving air through large cavities and direct air movement towards particular areas within the building. Stack effect caused by thermal conditions are excellent means by which air can be passively controlled through larger cavity voids, therefore minimizing the need for mechanical equipment. Stack effect is defined as the natural process by which air rises in a shaft or closed space when it is heated. The principles of stack effect are applied within the cavity of a double skin glass façades as a way of moving air naturally through the cavity and controlling air flow particularly for natural ventilation of interior spaces. A good example of an outdoor air curtain strategy that utilizes the stack effect is the GSW Headquarters building in Berlin-Kreuzberg, Germany, by Sauerbruch Hutton Architekten, completed in 1999. See Appendix A for case study analysis of this building as well.

Double Skin Glass Façades

Ventilation Types Within these five modes, there are variations that can be implemented in one or another type of ventilation strategy. Double skin glass faรงades can be either naturally ventilated, meaning that air flows into or out of the building skin cavity without the aid of mechanical device. A mechanically ventilated skin means that a mechanical system is used to assist the movement of air. By far though, the most popular type of ventilation type is a hybrid system that takes advantage of both naturally occurring air movement, such as the stack effect, and mechanically assisted air handlers.

Figure 12 Double Skin Glass Faรงade Ventilation Types Typical ventilation type systems depend on mechanical equipment, natural environmental conditions or a combination of both. This categorization illustrates their flexible nature in combination with other building and/or environmental systems.

Double Skin Glass Faรงades

Partitioning Types Vertical partitioning of double skin glass faรงades fall into either single floor height or multi story. Additionally, horizontal partitioning can be continuous or segmented as well. Horizontal partitioning is usually based on a modular window mullion system. Partitioning types include the boxed window, shaft box, single story and multi story.

Figure 13 Shaft Box Strategy

Figure 14 Boxed Window Strategy

Double Skin Glass Faรงades

Single story glass facades, as the name suggests, span only from floor to underside of floor above. Stack effect is better controlled due to the short distance from floor to ceiling on each floor. By necessity though, this type of system often requires mechanical assistance in order to realize the potential in envelope performance. Levine Hall, in Figure 11, mentioned earlier is an example of multi story faรงade, while the Stadttor, City Gate is an example of a single story partition system with interior operating windows spanning floor to ceiling.

Figures 15 Single Story Strategy

Figure 16 Multi Story Strategy

Double Skin Glass Faรงades

Strategies Double skin glass façades are not a panacea or silver bullet in and of themselves. The greatest benefit is when they are considered holistically during the schematic design and development phase of a building in order to appreciate the full extent of the benefits. By holistic I mean taking into account all aspects of design and building energy performance options as sustainable design principles. Designed with other energy management solutions in mind, such as building orientation, daylighting and natural ventilation, double skin glass façades have been proven to contribute to the savings on energy bills over several years of occupancy11. The following strategies illustrate the benefits of double skin glass façades when implemented with sufficient knowledge of building science and environmental forces.

Thermal Strategy Solar radiation creates a condition within the cavity known as The Stack Effect. This effect can be described as the natural lift condition that occurs when air is heated. The molecules of the heated air become agitated and spread further apart from each other, forcing the lighter, warmer air to rise and the cooler air to sink. As air rises, the performance characteristics of the double skin glass façade cavity are related to the measure of thermal control. Air shafts, vent, ports and window openings are four common passive design strategies employed to harness the power of stack effect principles.

Figure 17 Thermal performance diagram Thermal performance is measured by the amount of heat and moisture build up and distribution is maintained within the cavity

The natural stack effect of thermal air movement of a multi-story double skin glass cavity can be used to draw heat away from the interior of a building during warmer months, or to collect heat within the cavity for distribution within the interior spaces during colder months. For multi story façades, it is important to model the height of the building, as it is natural for upper floors to be in advantageous or disadvantageous conditions as heat accumulates in the upper portion of a cavity due to this stack effect. This can be a reason for choosing between a single story or multi story partitioning scheme. The performance of the thermal strategy is measured by how much heat capacity the cavity can retain in colder winter months for distribution within the interior rooms, and conversely reducing heat gain during the summer months to reduce the effects of thermal loading of interior spaces.

Double Skin Glass Façades

Incidentally, thermal mass storage is a benefit and can be considered as part of a double skin glass façade strategy. Thermal mass storage, as the name suggests, is the ability for materials to retain heat. In concrete slab construction, floors or ceilings near the perimeter of the building can be left bare. During sunny winter days, the slab heats up. At night, the heat retained in the slab slowly dissipates back out to the rooms. This strategy is useful in saving energy as the cost of reheating a building in the morning can be reduced. A strategy in reverse to this called night cooled mass can be used to absorb heat during the days when ventilation may not be adequate, and then cooled at night with ventilation. The key is to know the local conditions of the site and choose materials wisely while developing a strategy.

Figure 18 Air pressure difference in cavity, drawn by the author, adopted from Double-Skin Façades, Integrated Planning by Oesterle Pressure differences in height combined with thermal changes in the cavity due to the stack effect need to be predicted against existing environmental conditions, such as temperature and moisture, in order to determine such issues as cavity depth, vent sizes and window opening dimensions.

Coupled with vents designed into the exterior skin, operable windows designed into the interior skin and a mechanical system such as forced air, the net effect of the double skin façade’s ability to perform as an integral building system is defined by the performance against a standard curtain wall. The energy it takes to run mechanical equipment when a double skin glass façade is used must be less than that of a standard curtain wall without the cavity.

Double Skin Glass Façades

Natural Ventilation Strategy Natural ventilation is a popular strategy for double skin glass faรงades as I found during a building survey included in Appendix B. In this strategy, fresh air from outside is brought into the building either through operable windows or vents. This has the benefit of reducing the need on costly mechanical equipment. For example, if natural ventilation is allowed to occur, the need to air condition a building through mechanical means can be reduced thereby saving on energy usage. Natural ventilation is also becoming a hot topic in response to healthy buildings. A healthy building can be thought of as a healthy place where people work or live. In sustainable design terms, it is a measure of the condition of the place that people work in. This is sometimes measured by productivity or number of sick days per occupant of building. The fewer sick days, the healthier a building is considered12.

Figure 19 Natural Ventilation diagram Prevailing winds can play a vital role in establishing performance measurements for natural ventilation within a building. Coupled with narrow floor plates, cross ventilation has been shown to improve air quality and reduce dependence on costly mechanical equipment

Buildings, particularly high-rise buildings, are prone to varying degrees of negative and positive wind pressures. On the leeward side of a building, negative pressure can build up quickly in gusts of wind, while in windward sides, positive air pressures can build. A concern for designers is high winds, or the opposite, static pressures, that can build up on the face of a building and produce unwanted effects. In considering the application of naturally ventilated interior office spaces, pressure differences require careful planning not to create problems such as difficulty in opening doors, and papers blowing off desks. For example, a tall round building has different characteristics in response to wind than a square building. The corners of buildings usually create breakaway airstream patterns behind any corners set at right angles to the wind13. If the criteria for the building design require air flow from outside to the inside, the negative pressure created at these corners can have significant impact on window or vent placement of the double skin glass faรงade.

Window Operation Because natural ventilation is a major theme for double skin glass faรงades, operable windows on the interior skin are often considered as part of the strategy. Occupants should have the option of opening or closing these windows without significant impact on the overall performance of the building. A good example that allows for individual interior window operation is Stadttor, otherwise known as the City Gate, in Dusseldorf by Petzinka Pink & Partners. See Figure 20. The full interior height glazing system swings open to allow natural ventilation as well as cavity access.

Double Skin Glass Faรงades

Figure 20 Stadttor, Photo Credit, Petzinka Pink & Partners

It should be emphasized that in order for individually controlled operable windows to be a successful strategy for natural ventilation, occupants and building maintenance crews need to be educated as to the importance of managing the opening and closing of windows throughout the day. It would be counterproductive if occupants left windows open at night, or if windows were not opened, when environmental conditions are optimal to do so. In an ideal situation, individually operable windows might also be controllable through computerized building information and management system. The drawback with this scenario is the initial cost of additional electronic controlled system, automated mechanisms and ongoing maintenance and monitoring.

Daylight Strategy The strategy for controlling daylight although not problematic requires additional thought when it comes to additional layers of glass on the building envelope. Consider for a moment the amount of light that glass absorbs and reflects leaving a percentage of penetration within the space. The percentage is small, but it should be considered especially with tinted or chemically coated glass. Extra depth for the cavity is reduces the depth by which daylight can penetrate into deeper rooms. Daylighting requires additional considerations in order to maximize the potential for a double skin glass façades’ performance. Good practice includes maximizing glass surface area to allow as much natural light penetration into the rooms as possible. One method for controlling daylight and glare is to use perforated or solid shading system. These are often introduced in the interstitial space and controlled through mechanical devices.

Figure 21 Natural Daylight diagram Natural daylight can penetrate deep into a room with the aid of large glass surface area, reflective paint colors and the use of light shelves. The added depth of the cavity needs to be calculated for daylight penetration into rooms.

Double Skin Glass Façades

Narrow Floor Plate Strategy Before the proliferation of the electric light bulb and mechanically controlled interior spaces, commercial buildings were designed on a narrow floor plate in order to take advantage of the benefits of natural daylighting and natural ventilation. With the narrow floor plate, office spaces and work spaces were more likely to be located nearer windows. The advantage was evident in keeping the areas cooler in warm summer months through cross ventilation and bringing in natural daylight throughout the work areas. This strategy was all but abandoned in favor of electric lights and air conditioning. As double skin glass faรงades have the advantage of large areas of glass walls, when combined with a narrower floor plates, the large glazed areas allow light deep into the rooms and properly designed operable windows or vents on opposing walls can help with natural cross ventilation. For this reason and as part of sustainable building design practice, narrow floor plates are preferred over deeper ones.

Sound Strategy Double skin faรงades can be effective in deadening sound from external sources. Depending on floor plan configurations though, double skin faรงades may not be effective enough as primary sound insulation techniques between adjacent rooms. For example if the cavity is open to adjacent rooms, it is also open to sound transmission as well. This requires analysis of STC rating requirements to determine if there is a need to mitigate potential noise problems. However, the opposite holds true in corridor partitioning scheme. If in a partitioned corridor it is desirable to split the perimeter bays into offices, typically done at the curtain wall mullions, controlling sound between offices can be mitigated, as there is also separation in the cavity between the office zones. If sound control is a critical factor between perimeter offices, corridor cavity schemes should be considered.

Figure 22 Typical cavity corridor schemes The cavity plan on the left has a glass partitioned cavity while the cavity plan on the right is continuous. As can be seen, if there is noise being generated in an adjacent office, the potential for that noise to travel across to the other room can be problematic.

Double Skin Glass Faรงades

Planning Controlling natural ventilation by channeling air circulation between building skin layers also necessitates managing moisture control, analyzing the effects of thermal conductivity and responding to daylighting for human productivity. These concerns require prioritization based on environmental conditions and utilization demands. There are many questions to be asked when choosing to include double skin façades to envelope a building. What best methods should be used to filter natural air throughout parts of a building, and should natural air be introduced at all? How would double skin façades interface with mechanical building environmental controls for a specific climate? What solar control devices should be used, if any are to be used at all, and what optimum heat gain or heat loss techniques are best suited? Not least of all is to determine what types of double skin façades are used in particular climates. Most sources regarding the use of double skin façades agree that they are best used in situation of colder climates, high winds, to take advantage of natural ventilation and air flow through buildings, and areas prone to unwanted exterior noise, since they provide a good sound barrier. Although the interstitial buffer zone also serves as a good thermal control factor, it is most effective when sun shades are introduced within the cavity. The size of the building is not a critical factor in deciding whether or not to use a double skin façade; they can be equally effective in low rise building as in high rise buildings. Several factors affect the potential for a successful implementation of a double skin façade. In order to minimize dependency on air conditioning, Oesterle, Lieb, Lutz & Heusler, in the book Double Skin Façades, raise these concerns. “Quality of air supply, adequate sound insulation, adequate opening areas in the façade and the air change in the rooms”. They go on to say that “…ventilation should be possible throughout the year and an adequate conditioning of the internal spaces should be provided by other systems (e.g. radiators and/or cooling soffits)”14. This opens up the question as to the viability of using double skin façades in every instance. Conditions need to be right in order to maximize the potential of double skin glass façades.

Double Skin Glass Façades in High Rise Design My thesis is relevant for all building types and sizes, from low to high rise. However, I am particular interested in high-rise buildings, as they tend to use considerable amount of energy to run and I believe this area can prove the most cost effective application. According to James Wines “…the skyscraper is the most anti-ecological of all building types”15. By this, he refers to the amount of energy it takes to run elevators and the amount of redundant floor space required, such as vertical cores and repeat corridors on each floor. Taken literally, there is an inherent flaw in the thesis when applied to high-rise buildings. But Wines’ refers to skyscrapers, as we know them, how they have been built in the past. Part of the research aims to look at how high rise building skins are designed in order to reverse the trend of poorly performing taller buildings. There are benefits to high-rise buildings though. Ecologically minded architects strive to disturb as little of the land as possible, as the footprint of a skyscraper is very small in comparison to the number of square feet total. Double skin glass façades can begin to address at least a part of the environmental issue by reducing the amount of energy required to run skyscrapers. Double skin glass façades are part of a solution to change how energy is consumed by skyscrapers, all buildings for that matter. Their aim should be to provide balance to the amount of energy it takes to manufacture components, install the skin and run the facility, otherwise known as embodied energy. Embodied energy is the science of calculating how much total energy is consumed to produce and run something. This thesis is not focused on embodied energy, but as a sustainable measure, it is worth noting.

Double Skin Glass Façades

Selection Process An analysis of existing local climatic environmental conditions with a mechanical or environmental engineering team during schematic design phase is the best time to investigate which mode and type may be best suited for an application. A design approach known as Concurrent Engineering brings together specialists early on in the schematic design phase of a project to hash out several aspects of the building’s designs. There is no one prescribed mode that is better than or worse than the other as far as performance is concerned. Local climatic data, such as sun path diagrams showing sun path travel throughout the year and wind rose diagramming identifying average wind direction and speed as well as the average sun hours per day, are all used to inform the design team of an initial approach for optimal performance. See Figure 33 for examples of sun path & wind rose diagrams. This information can be used to address occupant comfort with respect to natural ventilation or cross ventilation strategies, wind patterns, solar angles for daylight strategies, and solar capacity for thermal performance strategies. The selection process begins by first establishing some performance criteria, such as occupant comfort range in temperature and relative humidity, u-value of glazing, air flow and air pressure requirements for cavity and venting strategy of the cavity. A comparison between standard glass curtain wall construction and a double skin glass façade should be made to determine if extra up front costs are justified through longer term energy savings. The strategy should also address whether the interior spaces will require venting all year or part of the year. Next, develop the design to address the criteria by making some informed decisions about the type and mode of the façade to be considered. By using computational fluid dynamic modeling, or better known as CFD analysis, which is not part of this thesis, a model of a proposed façade can be tested and evaluated for performance. Any adjustments and refinements can take place and re-evaluated. The process should continue this way till all requirements are met. CFD is an advanced computational method of predicting air flow and thermal loading of a given volume. It is typically used in predicting air and thermal behavioral patterns in cavities. A typical CFD analysis can determine how much air flow is caused by the stack effect due to solar radiation against a certain type of glass skin. In this way, venting or window placement can be sized accordingly. In terms of selecting a specific type of double skin glass façade, where natural ventilation is an objective, the air supply mode would be a good choice. If a heat recovery system were to be considered as part of the cavity, an indoor air curtain would be a good selection. For high-rise buildings that require natural ventilation a combination outdoor air curtain and air supply mode would be advantageous. Since multistory cavities are difficult to predict in thermal and air flow behavior, single story partitioning is generally preferred. In a survey conducted, see “Appendix B: Survey”, the most common type of double skin glass façade was found to be the hybrid multi story outdoor air curtain taking advantage of natural forces when possible and mechanical system operation when needed. As part of the selection process, mechanical systems should be considered early on. As this thesis is focused on hybrid types, mechanical equipment should be determined and sized according to the requirements set out for occupant comfort levels. Air handlers may be required to move air through the cavity for days that no prevailing winds are available. Moisture control equipment may be required to handle any predicted moisture build up within the cavity. Hydronic radiant floor or ceiling systems are becoming more popular in commercial applications. This thesis proposes such a system as part of the strategy for heating in the winter mode. Cost benefits can be estimated by such methods as life cycle analysis or net present value calculations. As part of this thesis, I have prepared a net present value model, see “Part 4: Net Present Value Modeling”.

Double Skin Glass Façades

The goal was to take a simple box building and calculate the additional cost of a single wall on a single floor for a double skin glass façade as compared to a standard curtain wall. Factors such as extra maintenance, energy price increases, extra material and installation costs were figured in to estimate how long it may take to recover the additional up front, or green costs, for the added double skin glass façade.

Re-Skinning An area that has great benefit by the use of a double skin façade is in retrofitting existing exterior building skins that require considerable envelope upgrading. The look of frameless glass for the exterior new skin offers an opportunity to rethink the architectural characteristic of a building. Additional glass building skins can add weather protection. Older masonry or wood frame walls tend to be problematic with respect to air barrier and insulation conditions. Mechanical equipment can be upgraded if there is sufficient ducting capacity and mechanical floor area. The extra skin with the integration of an efficient mechanical unit can provide good value. This can include heat recovery, thermal mass activation of solid elements, and less dependence on mechanical heating. Figure 23 shows the potential for a retrofit with an extra glazed layer. This in effect can be considered a box window type double skin glass façade. Re-skinning is mentioned as a footnote for potential application, but is not investigated as part of this thesis.

Figure 23 Re-skinning Existing Buildings Existing buildings, particularly ones with balconies, can be skinned in glass utilizing the same strategies as conventional double skin glass façades to achieve better performance.

Double Skin Glass Façades

PART 3: Program and Performance Project Design & Strategy A project with a double skin glass façade strategy was investigated in order to illustrate the potential in high performance buildings. The strategy is based on wind, or air flow, thermal convection, solar massing and daylighting. The site is intended to be a generic setting in Syracuse NY. This area offers the right climate conditions, cold windy for much of the year, to demonstrate the potential of double skin glass façades. The project is to be a twelve story commercial tower with the west and south walls as double skin glass façades.

Building Form & Aerophysics The process begins by exploring basic shapes in plan and elevation. Starting with primary building forms and experimenting with wind patterns helps to inform what the overall building shape wants to be. This is based on existing local climate conditions. Specific design requirements for occupant comfort will be discussed later. The science of air circulation, or air flow, about a structure’s form can serve to inform the overall shape of a building for the optimum design approach of a double skin glass façade depending on what the designer is trying to accomplish. For this project, I am looking for cross ventilation strategy, therefore wind patterns against the building should facilitate the potential for natural air flow without causing much turbulence.

Figure 24 Plan & Elevation building shapes

Double Skin Glass Façades

Figure 25 Volumes for Building shapes The shapes are extruded into volumes and can be use for wind flow analysis

The forms are put through air flow software and analyzed for positive and negative air pressure differences around a building volume.

Figure 26 Wind Flow Modeling The darker areas reflect high pressure buildup zones. In the images above, as high winds drive into the curved form on the right, it is expected that the low pressure zones on the left will assist in pulling air through the building.

Double Skin Glass Faรงades

Figure 27 Air Flow modeling about a curved form

Figure 28 Air flow patterns These patterns represent the different forces at work on bottom, middle and top zones of a tower.

Double Skin Glass Faรงades

Skin Shape Diagramming Exploring skin shapes opens up opportunities to test theories of air flow and thermal convection to see how air movement is affected within different shapes of a cavity. Lofting and extruding techniques are applied, and surface texture is created. The idea of ports or valves is then introduced as a means of developing an approach to how natural ventilation will eventually be integrated into the envelope scheme.

Cavity shapes in plan and elevations

Figure 29 Cavity Plan & Section diagrams

Double Skin Glass Faรงades

Volumetrically lofted and extruded shapes

Figure 30 Volumetric lofted & extruded shapes A progression of shapes in volumetric proportions generated through lofting or extrusion. Further experiments conducted on numerous shapes derived from lofting express physical patterns.

Figure 31 Volumetric lofted & extruded compound shapes

These shapes explore uniform lofting and extruding by progressively adding either faceted or waved contours to the faรงade. The blue and red boxes are representational of ports, or valves, that will later be taken into consideration when planning for venting patterns. Vents are typically used to move air into or

Double Skin Glass Faรงades

out of the cavity of the faรงade. These representational vents can either be fixed in one position, or for more refinement of the system, can be controlled mechanically to open or close to allow natural air flow into or out of the cavity. For the first pass of the project, the vents are considered static open. In subsequent analysis or testing, possibly using CFD modeling, the vents can be testing in closed or partially closed position to determine how air exchange rate in the cavity affects performance. CFD analysis was not conducted as part of this thesis.

Figure 32 Lofted forms with ports

Further analysis of the skin for venting pattern on a curved or wavy surface and a more angular faceted surface is shown in Figure 32. What I would eventually look for is the way in which prevailing winds might be affected by the surface texture of the skin. This may lead to further refinement of the concept of lofting of a skin shape. Wind conditions from various angles can begin to define how the venting strategy for the building will eventually be implemented. For example, if air is driven from the west for the faรงade, angled louvers can take advantage of the natural flow of air with less air resistance.

Double Skin Glass Faรงades

Project Design & Planning • • • • • •

Develop a scheme that demonstrates double skin glass façade strategies Assume standard office bay planning module at 5’ x 5’ for work space conformity, from “Building Type Basics for Office Buildings” by Eugene Kohn & Paul Katz Workspace desks to be within daylight proximity of exterior walls to maximize daylight potential Typical Floors 10’ ceiling height (office & research) for greater daylight penetration (typical is 9’) Approximate 12’ 6” foot to floor height for equipment integration into floor slab or plenum Basement levels assumed, no parking within building footprint

Typical single layer glass causes 10% reduction of natural light. Use of high transparency flint glass will be 7% to 8% reduction of natural light Slight reduction for thicker glass in structural applications

Climate & Meteorology The first order of business in designing a well performing double skin glass façade is the task of gathering meteorological and climatic data from the immediate vicinity. The data will be used to identify such issues as the best orientation of the façade, the potential for natural air flow within the cavity with respect to prevailing winds, solar heat gain with respect to sun angles and average sun hour days.

SOLAR DATA: LONGITUDE = 75° LATITUDE = 43° SUMMER SOLSTICE SUN ANGLE @ 73° WINTER SOLSTICE SUN ANGLE @ 26° AVERAGE SUN HOUR DAYS = 4

MEASUREMENTS FROM JULY 1 - SEPTEMBER 30 WIND SPEED DATA TAKEN FROM TMY2 SYRACUSE ROCK CUT ROAD, SYRACUSE, NY CALM, NO WIND 3.5% OF THE TIME HEAVIEST WINDS NW @ 12.5% OF THE TIME SOUTH WINDS @ 11% OF THE TIME LIGHTEST WINDS, NE @ 1% OF THE TIME

Figure 33 Sun Path & Wind Rose diagrams A Sun chart diagram on the left and a wind rose diagram on the right for a specific location, these are for Syracuse NY. The data is used in building skin performance analysis

Double Skin Glass Façades

Basic Double Skin Glass Façade Envelope A double-skin glass façade envelope consists of two glass curtain wall systems separated by a cavity of some distance. Cavity size and the ventilation of the cavity can be investigated through modeling software using known environmental data and prescribed criteria, such as occupant comfort levels. Ventilation attributes, such as intake or exhaust vent locations, sizes and orientation need to be sized according to this criteria. For example, if a certain air temperature and moisture content range is defined as part of the performance criteria, air vents on the exterior portion of the skin can provide the necessary amount of air flow through the cavity to assist in maintaining that range. In this project, an air temperature range for interior comfort conditions is assumed to be between 66°F & 72°F.

Figure 34 Analysis of air flow A 3D model analyzed for air flow within the cavity.

Figure 35 Double Skin Glass Façade Section diagram A prototype section of a double skin glass façade with a wide cavity and naturally vented ports occurring every other floor. The system is also designed as a double story high module for installation economy

Double Skin Glass Façades

Figure 36 Model Envelope with louvered vents A 3D model of a double skin glass façade with a 3’ cavity and operable intake and exhaust vents is shown. The exterior skin louvers are curved downwards to shed rain water.

Figure 37 Modular Façade Elevation Wind rose diagramming shown earlier indicated prevailing winds from the south and west. This indicates the pattern on the façade represented by the blue arrows across the front. The supply and exhaust, also indicated by blue and red vertical arrows respectively, are positioned in alternating pattern to prevent exhaust air from sweeping back up into the supply grilles.

Double Skin Glass Façades

The Site Plan The site plan below shows three different building schemes in a complex. Scheme A’ is a twelve story tower shown in plan that will be explored further as part of this thesis for the double skin glass façade properties. This scheme is based on wind and air flow strategy with thermal and daylight emphasis. Two additional schemes are also included in the plan below only to illustrate that various strategies can be alternated in degree of importance of performance. In other words, each strategy can work as a lead or main emphasis for design criteria in combination with the other strategies. Scheme B’ was conceived as thermal strategy with daylight emphasis, and Scheme C’ was conceived as daylight strategy with ventilation and thermal emphasis. These last two schemes have not been developed as part of the scope of this thesis.

Figure 38 Building & Site Plan Site Plan showing three schemes, each a manifestation of a double skin glass façade strategy: Natural Ventilation, Thermal Mass and Daylight.

The suns movement is plotted to determine the extent of shading on the different faces of the building, this might come from other buildings near by or from the form that the building takes.

Double Skin Glass Façades

Figure 39 Typical Tower Floor Plan

The shape of this floor plan was selected during the building mass exploration because of the way air pressures build up on the west curved face, where the double skin glass faรงade is located. Since the east side of the building has less air pressure buildup, a natural air flow would tend to be pulled from east to west. The west wall cavity will have vents located and sized to regulate air pressure by the stack effect method throughout the year in order to facilitate natural cross ventilation.

Double Skin Glass Faรงades

Tower Scheme This scheme is based on a natural ventilation strategy with daylight and thermal emphasis.

Figure 40 Performance Design Criteria

Tower Program •

• • • •

Double skin glass façade on west and south elevations, east elevation louvered double skin for cross ventilation Twelve stories with narrow floor plate scheme Varied width floor plate approximately 40’ to 100’ wide by approximately 300’ long Lobby ceiling height 15’ - possible atrium or light well Interstitial space range from 3’ width for maintenance and balcony access to 12’ width for green zone recreation and break area

Building Skin • The skin will be broken up into single story and multi story corridor type partitioning • Air supply and air exhaust mode is proposed • Hybrid ventilation will take advantage of natural ventilation, stack effect and mechanical air handlers with moisture control equipment provided • Winter Operation o Inner façade closed, but may be opened by user for natural ventilation o Interstitial space acts as buffer zone o Heating by mechanical radiant augmented by solar thermal conductivity o Shade system retracted for solar heating o Preconditioned air of interstitial space captured into heat recovery system for preconditioned air to maximize efficiency operation • Summer Operation o Inner skin operable for natural ventilation o Stack effect venting per floor o Shade system extended to block solar gain, reduced solar radiation to inner skin

Double Skin Glass Façades

Ventilation • Operable inner façade, fixed vented exterior façade allowing for naturally ventilated partitioned cavity • Stack effect managed through multi story and single story partitioned cavity • Narrow floor plate allows for better cross ventilation and daylighting Daylighting • Daylight reduction factor needs to be considered due to extra layer of glass • Daylight room depth penetration reduced due to façade cavity width • Larger area of glass means greater depth of light penetration • Light deflecting elements in façade cavity integrated with perforated shading to control glare but allow daylight penetration into office space • Work space desk height consideration for daylighting requirements • Evaluation strategy through solar tracking software for exterior shadow casting and interior daylight penetration Thermal • Partial exposed concrete slab near perimeter for thermal loading • Stack effect at multi story partition cavity • Mechanical air handling system integrated with façade • Shading in cavity to control thermal loading • Thermal massing of concrete slab near perimeter of building Cost • • • • •

Extra expense due to depth of cavity and extra glazing layer Additional design and engineering fees Concentration on functional space between cavity creating atria of usable space Savings based on energy savings of electricity for daylighting strategy, mechanical costs due to reduction of lighting needs, and efficient integrated radiant heating system Evaluation to be based on average mean costs of similar projects not incorporating green building and double skin façade measures, Means Construction Cost Data as part of evaluation

Figure 41 Perspective view of building with faceted skin

Double Skin Glass Façades

Figure 42 Site shadow studies

Figure 43 Cross Section of tower with Wind Strategy

The plans, sections and strategies proposed are used as a starting point for the investigation of the potential for the double skin glass faรงade on the west and south walls of the tower.

Double Skin Glass Faรงades

Figure 44 Year round mode daylight strategy

Figure 45 Heat recovery strategy – Winter Operation

Figure 46 Ventilation strategy – Summer Operation

Double Skin Glass Façades

Figure 47 Standardized detail for double skin glass facade

A Prototypical design is made up of components for mass customization. Louvers in the interstitial space control how much solar radiation is let into the cavity. Vents in the curtain wall frame allow integrated systems design. Air flow through operable windows in the rooms allow for natural ventilation. Perimeter vents allow for air infiltration from lower angles thus providing an opportunity to utilize thermal mass when possible. Thermal mass is proposed as a means of storing heat during the day by preheating portions of the interior concrete perimeter from solar radiation, and allowing the heat to dissipate slowly into the rooms at night relieving the need to fully heating with mechanical equipment.

Double Skin Glass Faรงades

Faceted Surface Texture

Figure 48 Rough surface texture cavity shape

Single Bay Design Development

Figure 49 Faceted Form Module The bay takes on a faceted shape

Figure 50 Single Bay Modules Single bay faceted options are developed with venting strategies based upon prevailing wind patterns, in this case from parallel to right angle to the faรงade. Data are obtained by using wind rose diagrams created for the area.

Double Skin Glass Faรงades

The next step is to identify width and height of cavity. As mentioned earlier, this can be accomplished by simulation using CFD analysis. Air flow and thermal conduction and convection are considerations for the evaluation criteria. We want consistent heat and air flow throughout the cavity. Too much heat buildup may negate the benefit of the faรงade. Too much air flow may cause positive air pressure build up and unwanted effects such as opening windows for natural ventilation and getting too much air blowing through. We are also looking for any anomalies, such as sporadic air movement, or down drafts. The goal is to design for consistency and predictability in overall thermal heat gain, heat loss, thermal mass build up and natural ventilation.

Figure 51 Cavity thermal distribution The predictions can be tested with mock up or CFD modeling to determine more precisely how air flow affects thermal distribution. This is a good indicator for sizing and positioning of vents and selecting the types of shading devices for best performance.

Figure 51 shows thermal distribution in a slice of a single bay for a faceted design. Operable shading devices can be used to adjust the amount of heat build up within the faรงade, while the natural occurrence of stack effect can be used to distribute or dissipate the heat through exterior vents as needed.

Double Skin Glass Faรงades

Figure 52 Faceted wall

When multiplied across the faรงade, the faceted single bay begins to take on a rough textured surface. Responding to prevailing wind conditions, this wall presents an opportunity to test how intake air through vents on the front and outdoor vents on the sides of the skin can react to positive and negative air pressures.

Double Skin Glass Faรงades

Figure 53 Faceted Skin Section The air intake vents serve to provide air flow through the cavity, in turn, interior conditioning can occur through vents in the perimeter of the inside face of the skin.

Double Skin Glass Faรงades

Figure 54 Building Elevations for faceted surface texture scheme

Double Skin Glass Faรงades

Curved Surface Texture The cavity can be used either strictly as a utilitarian area for service or may be expanded to become an interstitial habitable environment for balconies, or areas of refuge for high rise buildings. This scheme explores the architectural spatial relationship between cavity and occupy-able space.

Figure 55 Wavy or curved surface texture cavity scheme

Figure 56 Wavy or curved formed surface with contoured vents

Double Skin Glass Faรงades

Figure 57 Habitable environment within vented cavity

Figure 58Air flow prediction w/ contoured vents

Figure 59 Venting the Skin

Double Skin Glass Faรงades

Figure 60 Wavy or contoured curve formed surface with ports

Double Skin Glass Faรงades

Figure 61 Habitable environment within ported cavity

Figure 62 Air flow and thermal prediction w/ contoured ports

Double Skin Glass Faรงades

Figure 63 Venting the skin using a port

Figure 64 Building Elevations with contoured wavy port surface texture scheme

Figure 65 Strategy Technology Matrix Elementary Facade is on the left and interstitial environment matrix is on the right

Double Skin Glass Faรงades

Performance Criteria for Evaluation The performance of double skin glass façades is based upon controlling indoor comfort while minimizing energy usage. The harnessing of passive solar power, or thermal performance, is one strategy of the double skin glass façade. Controlling natural air flow, natural ventilation and the management of daylight are other strategies. A benefit of the double skin glass façade is that conditioning spaces within the building can be augmented by drawing from or contributing to thermal and wind energy stored within the cavity. The sustainable principle of the conservation of natural resources says that the use of free natural energy is preferred over costly non-renewable natural resources. Criteria for performance are therefore related directly to human comfort within the interior building spaces with minimal disturbance of natural fossil fuels. The performance of a double skin glass façade is based upon its ability to maintain cavity conditions and reduce energy usage that buffer the internal rooms from the external environment in varying degrees based upon specific measurements set up in determining the range of human comfort. In order for proper evaluation to occur, a standard curtain-wall system should be evaluated as a baseline. Simulation of the baseline should be done for the exact climatic conditions as for testing of the double skin glass façade. Construction components of the double skin glass façade should be comprised of known cavity dimensions of width and height. U value for single pane exterior glass and U value for double pane interior glass including any argon filling or low-e coatings should be counted. Several tests should be conducted to simulate conditions throughout the day with changing solar angles against the glass wall, outdoor temperatures and moisture content or relative humidity within the cavity. The performance of a well designed double skin façade depends on the dimensional depth of the building and solar orientation of the glass façade. Component or modular component size is also of concern, as well as glazing color that affects solar radiation and daylighting potential. The aesthetics of the building are dependent upon all these factors and play a role in working out specifics for the logic behind form.

Figure 66 Performance Considerations diagram Performance criteria are based upon a number of factors as shown on this illustration

Double Skin Glass Façades

The cost of material and installation for a double skin glass façade is greater than standard curtain wall construction, therefore, a reasonable return on investment over time through energy savings and occupant productivity are critical to their success. This puts the performance of the double skin glass façade into energy efficient or high performance building category and must be evaluated against this for human comfort. In Part 4, I have performed some simple net present value calculations to compare costs of double skin glass façades against standard curtain wall performance over time.

Analysis Mechanical equipment such as air handlers, air exchangers, and/or hydronic radiant piping each constitutes alternate solutions that are integral to designing a hybrid ventilated façade. The strategies for successful implementation of double skin glass façades are summarized. Summer mode operation will consider vents in the exterior glass layer in the open position, interstitial space shades in extended position and air flow through the cavity regulated to cool the interior space. The regulated air flow is necessary in order to prevent too much air flow that can cause unwanted behavior, such as down draft caused by negative pressures or high velocity caused by too much pressure. Thermal Loading – Analysis consisting of solar heat gain for performance based on time of day and seasonal environmental changes. Mechanical equipment integrated with façade is taken into account. CFD modeling can be used to determine what thermal characteristics would be best suited for energy performance, such as amount of heat build up, heat dispersion and air flow within the cavity. The process is set up to determine cavity size in relation to vent openings. Ventilation – Analysis consisting of air pressurized zones and accountability for external environmental conditions to determine optimal building shape, and cavity partitioning. Known external air flow conditions against the building can be used to determine vent sizes and window operability. Vents are typically used in exterior skin of a double skin glass façade to move natural air into or out of the cavity. In some instances, vents are incorporated into the curtain wall frame, as I have proposed for this project. Potential for volume and velocity of air flow should be calculated in order to address the optimal width of a building footprint in relation to window or vent opening sizes. This is beyond the scope of this thesis. Daylight – Analyze building orientation and shape with respect to area of glazing for greatest potential of light penetration to determine optimal work conditions and minimal use of electric lighting. Minimize depth of building by proportioning it longer along north south axis where possible. South and west façades could be double skin glazed. Façade performance is dependent on glass composition that may affect optimum amount of daylight potential. Daylight or shadow casting software with local solar pattern data fed into it is preferable. Photometric charts can further assist in determining optimal luminosity of daylight penetration. Cost Analysis – Means Costs Data for Construction, similar projects of scope or size, national and regional averages based on square foot available, such as the Buffalo Niagara Builders Association. Present and projected energy cost is used to estimate potential savings or loss over time with respect to initial construction costs.

Double Skin Glass Façades

Test Case Parameters The following criteria were developed to establish parameters for measuring performance. Although I was unfortunately unable to procure an engineering resource to assist with actual computational fluid dynamic modeling, the CFD test set up is included to approach engineering resources later for analysis. It describes a procedural guideline for testing double skin glass façades.

Curtain Wall Components Used 1. 2. 3. 4. 5. 6. 7.

Single Pane exterior glazing with integrated fixed vents Double pane interior glazing with Low-e coating on interior surface of exterior pane, argon filled cavity Interior glazing operable for natural ventilation Interstitial space conditioned depending on width and use, i.e. no access, maintenance access or multi function useable space (room) Interstitial solar shading device, such as perforated shades for thermal, daylight and glare control External solar shading device to control extreme heat gain from hot summer sun Light shelf on interior space to direct daylight further into room

Mechanical Equipment Used 1. 2.

Heat exchanger can be evaluated in computer simulation and modeling methods to determine optimal installation and sizing Radiant floor or ceiling piping with individual control

Envelope as Wall or Habitable Space 1. 2. 3.

Buffer zone up to 6” interstitial space constitutes wall Buffer zone greater than 6” and up to 3’ interstitial space as maintenance corridor or small balcony Buffer zone greater than 3’ and up to 12’ interstitial space as habitable space, such as place of refuge or break area from office zone

CFD Test Set up Testing for buildings exterior shape for wind conditions Testing for buildings interior conditions 1. Testing for Ventilation and air movement for determining best use of mechanical equipment for human comfort range a. size of vents in exterior skin b. size of vents for interior skin 2. Testing for moisture control, relative humidity to prevent condensation and maintain human comfort range, dehumidification a. Condensation buildup of interior surface of exterior skin 3. Testing for Thermal Loading to determine best use of mechanical equipment for human comfort range a. Heat buildup and difference from once side of cavity to the other b. Heat buildup and difference from lower area of cavity to upper c. Different heights, from single story, 12’ tall to multi story, 60’ tall 4. Testing of shading options, vertical or horizontal louvers a. Shading on interior surface b. Shading on exterior surface 5. Testing of hydronic versus forced air heating elements, individually controllable where suitable application a. Components in cavity b. Components next to glazing on interior room

Double Skin Glass Façades

Criteria Range • • •

Low Temperature Range = 0°F - 32°F Medium Temperature Range = 33°F - 65°F High Temperature Range = 66°F - 95°F

• • •

Low Wind Speed = 0 mph - 9 mph Medium Wind Speed = 10 mph - 19 mph HIGH Wind Speed = 20 mph - 30 mph

• •

Indoor Temperatures Range 68°F - 72°F Indoor Wind Speed < 1 mph @ desk height

Ventilation Testing for Defined Shapes • • •

Wind load perpendicular to building Wind load angular to building Wind load parallel to building

• • •

Slow wind speeds Medium wind speeds High wind speeds

Evaluation Results: • Where are high pressure systems created • Where are low pressure systems created What tolerances allow air movement within cavity to be manageable for natural ventilation to occur, i.e. do not blow paper off desks when windows are open.

Thermal Testing for Cavity Width Testing of cavity space to include variable height and width combinations • Low Temperature No Air Movement • Medium Temperature No Air Movement • High Temperature No Air Movement • • •

Low Temperature High Air Movement Medium Temperature High Air Movement High Temperature High Air Movement

Pros & Cons of cavity widths Analysis of a double skin glass façade cavity is undertaken by categorizing the width of the cavity into narrow and wide areas. Height is critical in so far as thermal stack effect and air flow are concerned. The higher a cavity is, the more likely anomalies will occur, such as unexpected down drafts, or excessive uplift speeds. Conditions affecting pros and cons are listed for two zone sizes, interstitial space up to 6” wide and then up to 8’ wide. Buffer Zones up to 6” interstitial space Pros: • Aesthetic appeal for an all glass building • Less cost of construction than 8’ width

Double Skin Glass Façades

• • • • • • • • • • Cons: • • • •

Better thermal performance than traditional single glazed/double pane curtain wall assembly Better integration with mechanical equipment than traditional curtain wall Greater energy savings in thermal performance throughout building due to extra layer of glass and integrated mechanical equipment Greater energy savings due to less required electrical lighting because of daylight penetration More viewable area possible with less energy consumption required than traditional curtain wall Interstitial space can be used as air supply or exhaust plenum Preheated or preconditioned air can be managed within the interstitial space Thin wall allows for system to be modularized and custom mass produced as unit components for better cost control Interior glazing operable for maintenance Numerous shading option available for exterior surface application due to narrow interstitial space Daylight more restrictive due to extra glass layer, requires analysis of glass composition and type More cost of construction than traditional single layer double pane curtain wall Interior surface of exterior skin requires moisture control measures designed with hybrid or mechanical system integration Narrow interstitial space has more resistance of air movement than wider space

Buffer Zones greater than 6” and up to 8’ of interstitial space Pros: • Aesthetic appeal for an all glass building • Interstitial space can be used for multifunction, such as terrace or break room • Planting in interstitial space allows for more green environment on multiple levels of building and soften feeling of hard edges • Better thermal performance than traditional curtain wall assembly • Better integration with mechanical equipment than traditional curtain wall • Better thermal performance than traditional single glazed/double pane curtain wall • Greater energy savings in thermal performance throughout building due to extra layer of glass and integrated mechanical equipment • Greater energy savings due to less required electrical lighting because of daylight penetration • More viewable area possible for building occupants to the outdoors, but with less energy consumption required than traditional curtain wall • Interstitial space can be used as air supply or exhaust plenum • Passively preheated space in winter months • Possibility to control thermal loading on horizontal surfaces, i.e. concrete floor for heat retention in colder days, increased contribution of mass • Preheated or preconditioned air can be managed within the interstitial space • Numerous readily available shading option available for interior surface application due to wide interstitial space Cons: • Costly due to deep cavity, requires two separate installation components • More maintenance of useable space, longer term costs • Less revenue per square foot due to loss of rentable/saleable space • Daylight more restrictive due to extra glass layer and deeper interstitial space, requires analysis of glass composition and type • Interior surface of exterior skin requires moisture control measures • Deeper buffer zones requires deeper building

Double Skin Glass Façades

PART 4: Net Present Value Modeling The following calculations are based on net present value formula to determine what savings if any are possible when comparing a double skin glass façade against a standard single skin curtain wall on an 8 story building in Syracuse, NY.

Where: - “Co” is the value of any initial investment (usually a negative value). - “rate i” is the constant “cost of capital” per unit of time (x.x%/yr). - “n” is the number of time units (i.e. years) over which value is being calculated. - “value i” is the constant investment return per unit of time (in dollars). Net present value formulas like this one can assist in forecasting return on investment against higher initial green construction costs, such as double skin glass façades. In plain terms, the formula projects today’s dollar value over a period of time, (n), by adding in upfront green construction costs, (Co), and factoring in savings over time (value i) while also taking into consideration any cost of capital, i.e. bank loan percentages, (rate i). A simple box building was designed with the west wall a double skin glass façade. This cost of building this wall was then compared to a typical single skin curtain wall. Certain assumptions were made, such as productivity gains, to evaluate long-term financial effects. Modeling was done for 5% and 10% energy increase yearly for 10 years. Productivity gains were also calculated for 0% productivity and .5% productivity over the same 10 year period. Interest rate for loans was calculated at 0%, 5% and 10% interest. BUILDING STATISTICS Location: Downtown Syracuse, NY Latitude = 43° Longitude = 46°

ENERGY EFFICIENT DESIGN Floor to ceiling glass and tall floor to ceiling heights to increase daylight access results in reduced lighting needs

Total Floor Area Per Floor = 10,000 Sq. Ft. Core Floor Area Per Floor = 1,700 Sq. Ft. Double skin Interstitial Walkway = 300 Sq. Ft.

Double skin glass facade on west facade for natural ventilation and thermal control

Rentable Floor Area Per Floor = 8,000 Sq. Ft.

Mechanical equipment works less in summer and winter due to thermal control of west facade

WINTER OPERATION: Inner facade closed Flue acts as buffer Optional heating mechanical Shades pulled up to allow solar heating Radiant ceiling heating

SUMMER OPERATION: Inner skin opened Shaded pulled down to block solar gain Reduced solar radiation to inner skin Stack effect vents each floor Radiant ceiling cooling

Double Skin Glass Façades

Figure 67 Building Floor Plan for NPV modeling Floor plan outline of a building showing west wall as double skin glass faรงade

Figure 68 Building Elevation for NPV modeling Elevation and building section of a building for use in NPV calculations

Double Skin Glass Faรงades

Project Information

Calculated with .5% productivity savings

Project Title: Location: Stories: Basement: Construction:

Syracuse Office Central Syracuse NY 8 stories Not Included Precast Concrete Floors, Steel Frame, Curtain Wall 4 sides 1 side (west face) double skin façade Operable windows all floors Mechanically controlled shades within interstitial space of DSF Heating/Cooling plant in Basement & Roof

Glazing: Shades: Mechanical:

Summer Operation of DSF: Windows manually Operable by individual user Shades electronically controlled by individual user, switch on wall Naturally ventilated - Air flow through cavity and office for cooling Winter Operation of DSF: Heat Recovery through double skin façade Thermal storage mass Story Height Average:

12 feet floor to floor Average energy efficient office 3 - 4 watts/sf (6 or more standard) 80,000 sf x 3 = 240kW

Geographic Data: Sun Hours / Day Syracuse, NY

High 3.93

Latitude Longitude

43° 76°

Low 1.62

Average 3.16

Double Skin Glass Façades

National Grid Business Rate Chart: Customer charge Delivery charge (for 240 kW average) first 40 kW next 200kW = 200 x 16.61 Delivery charge (per kwh) 450 hrs max usage = 240 x .01039 System Benefits + Renewable Portfolio surcharge = (.1619+.0491) x 240 = .211 x 240

= = =

$ 664.40 $ 3,322.00 $ 2.49

Monthly electric charge

$ 4,299.68

Monthly charge average = $4,299.68 x 12 months Divided by 8 floors

= =

$51,596.16 $ 6,449.52

yearly per floor

Yearly Electric usage = $6,449.52 per floor 20% energy reduction per year for green design 1st year, then increase 5% or 10% yearly

$ 5,159.62 $ 1,289.90

Savings

Double Skin Glass Faรงades

260.15

50.64

Construction Cost Analysis with and without Double Skin Facade Low $

Cost Range w/o DSF: Total: OH&P: Design Fees: Total Building Cost:

$ $ $ $

6,960,000.00 1,740,000.00 470,000.00 9,170,000.00

Avr. $

High $

$ 8,265,000.00 $ 2,080,000.00 $ 565,000.00 $ 10,910,000.00

$ 9,570,000.00 $ 2,420,000.00 $ 660,000.00 $ 12,650,000.00

Avr. $

High $

Low $

Cost Range w/ DSF: Extra cost for DSF Total: OH&P: Design Fees: Total Building Cost w/ DSF:

$ 190,000.00 $ 6,960,000.00 $ 1,740,000.00 $ 482,625.00 $ 9,372,625.00

$ 335,000.00 $ 8,265,000.00 $ 2,066,250.00 $ 580,500.00 $ 11,246,750.00

Total glazing area per side = 100' x 96' = 9600 sq.ft. Additoinal cost of DSF $20/sf

$35/sf

$ $ $ $ $

480,000.00 9,570,000.00 2,392,500.00 678,375.00 13,120,875.00

$50/sf

For Syracuse Office Central, assume average costs for calculating NPV: Additional DSF cost @ $35 Average cost of base building Total Building Cost

= + =

$ $ $

335,000.00 10,910,000.00 11,246,750.00

/ 8 floors = $41,875 per floor / 8 floors = $1,363,750 per floor / 8 floors = $1,405,843.75 per floor

Construction cost for 1 floor

1,405,843.75

per floor

Design fees increase by $15,000 / 8 floors = $1,875 added cost per floor

(source: Construction cost and fee rates obtained from Means Construction Cost Data, 2006) for Syracuse NY Construction Cost Analysis with and without Double Skin Facade

Double Skin Glass Faรงades

NYS Tax Credit Data: NYS Tax Law Article 1. NY CLS Tax 19 Green Building Credit up to 1.4% credit component of capital costs up to 1.6% credit component in economic development area up to $2M aggregate total At $1,405,843 per floor - 1.6% = $22,494 savings = Includes commissioning built into base cost

$ 22,493.50

savings on taxes

Green Analysis per one floor of office building: Double Skin Faรงade Approx. $0.5M cost of lighting total - 3%

$ (41,875.00)

up front fixed cost

= $15,000 / 8 floors

1,875.00

savings on lighting install

Approx. $1M cost for HVAC total - 5% = $50,000 / 8 floors

6,250.00

savings on hvac equip.

Cleaning & Maintenance additional for DSF = $ (225.00) per cleaning 4 cleanings per year = $ (900.00) yearly (based on $0.75 per square foot, special maintenance from Double Skin Faรงades Manual) Rental space average for Syracuse @ $12/S.F. yearly Increased by 3% for Green Building Premium 8,000 s.f. per floor rental space x $12/s.f. = 8,000 s.f. per floor rental premium x $12.36 / s.f. =

0.36

$ 96,000.00 $ 98,400.00

/S.F. additional income Basic income Prime Green income ($2,400 savings add)

(source multiple listings, commercial leases, Syracuse NY)

Double Skin Glass Faรงades

Productivity Calculated at .5% Savings National Fire Protection Code allows for: 100 s.f. per occupant office space 15 s.f. per occupant conference room 8,000 s.f. per floor / 100 s.f. x 25% for aisles, conference rooms, etc. = 60 occupants per floor 60 occupants x average salary of $45,000 yearly = $2,700,0000 per year x 2 national average compensation overhead = $5,400,000 per year per floor of workers Acording to Katz study, page 111, direct productivity costs can save between .5% to 5%) for the purposes of this study, assume .5% productivity savings Assume Worker Salary increase of 5% yearly year 1 2 3 4 5 6 7 8 9 10

base + 5% increase $ 5,400,000.00 $ 5,670,000.00 $ 5,953,500.00 $ 6,251,175.00 $ 6,563,733.75 $ 6,891,920.44 $ 7,236,516.46 $ 7,598,342.28 $ 7,978,259.40 $ 8,377,172.37

difference 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5%

.5% productivity savings $ 27,000.00 $ 28,350.00 $ 29,767.50 $ 31,255.88 $ 32,818.67 $ 34,459.60 $ 36,182.58 $ 37,991.71 $ 39,891.30 $ 41,885.86

Double Skin Glass Faรงades

SUMMARY ANALYSIS FOR SINGLE FLOOR Summary of Additional Initial Upfront Costs & Savings DSF additional expense = Fees additional expense = Lighting cost savings = HVAC cost savings = NYS Tax Credit (savings) =

$ $ $ $ $

(41,875.00) (1,875.00) 1,875.00 6,250.00 22,493.50

Total Green Premium

(13,131.50)

Summary of Energy Savings & income over time yearly energy savings = yearly increased rental income = yearly additional cleaning costs = yearly increase productivity savings =

$ $ $ $

1,289.90 2,400.00 (900.00) 27,000.00

29,789.90

Total Savings yearly = (first year, before energy rate and worker comp increase) Note: Energy prices increase 5% yearly Worker salary increases 5% yearly Rental income same for 10 years Cleaning and maintenance same for 10 years

Double Skin Glass Faรงades

Energy Savings Energy Savings based on 5% energy increase per year Year Base 20% reduction 1 $ 6,449.52 $ 5,159.62 2 $ 6,772.00 $ 5,417.60 3 $ 7,110.60 $ 5,688.48 4 $ 7,466.13 $ 5,972.90 5 $ 7,839.43 $ 6,271.55 6 $ 8,231.40 $ 6,585.12 7 $ 8,642.97 $ 6,914.38 8 $ 9,075.12 $ 7,260.10 9 $ 9,528.88 $ 7,623.10 10 $ 10,005.32 $ 8,004.26

$ $ $ $ $ $ $ $ $ $

difference 1,289.90 1,354.40 1,422.12 1,493.23 1,567.89 1,646.28 1,728.59 1,815.02 1,905.78 2,001.06

Energy Savings based on 10% energy increase per year Year Base 20% reduction 1 $ 6,449.52 $ 5,159.62 $ 2 $ 7,094.47 $ 5,675.58 $ 3 $ 7,803.92 $ 6,243.14 $ 4 $ 8,584.31 $ 6,867.45 $ 5 $ 9,442.74 $ 7,554.19 $ 6 $ 10,387.02 $ 8,309.61 $ 7 $ 11,425.72 $ 9,140.57 $ 8 $ 12,568.29 $ 10,054.63 $ 9 $ 13,825.12 $ 11,060.10 $ 10 $ 15,207.63 $ 12,166.10 $

difference 1,289.90 1,418.89 1,560.78 1,716.86 1,888.55 2,077.40 2,285.14 2,513.66 2,765.02 3,041.53

Double Skin Glass Faรงades

Yearly Increases Energy Savings based on 5% energy increase per year year 1 2 3 4 5 6 7 8 9 10

energy savings $ 1,289.90 $ 1,354.40 $ 1,422.11 $ 1,493.22 $ 1,567.88 $ 1,646.28 $ 1,728.59 $ 1,815.02 $ 1,905.77 $ 2,001.06

additional rent $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00

maintenance $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00)

productivity savings $ 27,000.00 $ 28,350.00 $ 29,767.50 $ 31,255.88 $ 32,818.67 $ 34,459.60 $ 36,182.58 $ 37,991.71 $ 39,891.30 $ 41,885.86

Total savings $ 29,789.90 $ 31,204.40 $ 32,689.61 $ 34,249.10 $ 35,886.55 $ 37,605.88 $ 39,411.17 $ 41,306.73 $ 43,297.07 $ 45,386.92

productivity savings $ 27,000.00 $ 28,350.00 $ 29,767.50 $ 31,255.88 $ 32,818.67 $ 34,459.60 $ 36,182.58 $ 37,991.71 $ 39,891.30 $ 41,885.86

Total savings $ 29,789.90 $ 31,268.89 $ 32,828.28 $ 34,472.73 $ 36,207.21 $ 38,037.00 $ 39,967.72 $ 42,005.36 $ 44,156.31 $ 46,427.38

Energy Savings based on 10% energy increase per year year 1 2 3 4 5 6 7 8 9 10

energy savings $ 1,289.90 $ 1,418.89 $ 1,560.78 $ 1,716.86 $ 1,888.54 $ 2,077.40 $ 2,285.14 $ 2,513.65 $ 2,765.02 $ 3,041.52

additional rent $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00

maintenance $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00)

NPV = Value + (valuesi / 1+ratei)i

Double Skin Glass Faรงades

Net Present Value calculated with .5% productivity savings

Cost of CAPITAL @ 5% energy increase per year Interest Rate 0% 5% 10% $ 15,239.83 $ 13,950.23 1 $ 16,658.40 $ 43,543.14 $ 39,738.98 2 $ 47,862.80 $ 71,781.66 $ 64,299.17 3 $ 80,552.41 $ 99,958.47 $ 87,691.77 4 $ 114,801.51 $ 128,076.52 $ 109,974.49 5 $ 150,688.06 $ 156,138.61 $ 131,202.03 6 $ 188,293.93 $ 227,705.10 $ 184,147.39 $ 151,426.19 7 $ 212,105.41 $ 170,696.09 8 $ 269,011.84 $ 240,015.09 $ 189,058.27 9 $ 312,308.90 $ 267,878.72 $ 206,556.89 10 $ 357,695.82 ROI in all cases in 1st year YEARS

Cost of CAPITAL @ 10% energy increase per year YEARS Interest Rate 0% 5% 10% $ 15,239.83 $ 13,950.23 1 $ 16,658.40 $ 43,601.64 $ 39,792.29 2 $ 47,927.29 $ 71,959.94 $ 64,456.66 3 $ 80,755.57 $ 100,320.74 $ 88,002.00 4 $ 115,228.30 $ 128,690.04 $ 110,483.83 5 $ 151,435.51 $ 157,073.83 $ 131,954.72 6 $ 189,472.51 $ 185,478.15 $ 152,464.48 7 $ 229,440.23 $ 213,909.03 $ 172,060.29 8 $ 271,445.59 $ 242,372.58 $ 190,786.88 9 $ 315,601.90 $ 270,874.96 $ 208,686.64 10 $ 362,029.28 ROI in all cases in 1st year

Double Skin Glass Faรงades

NPV @ 5% Energy Increase Yearly & .5% Productivity Savings

ROI

0% 5% 10%

YEARS

NPV @ 10% Energy Increase Yearly & .5% Productivity Savings

ROI

0% 5% 10%

YEARS

Double Skin Glass Faรงades

Productivity Calculated at 0 Savings National Fire Protection Code allows for: 100 s.f. per occupant office space 15 s.f. per occupant conference room 8,000 s.f. per floor / 100 s.f. x 25% for aisles, conference rooms, etc. = 60 occupants per floor 60 occupants x average salary of $45,000 yearly = $2,700,0000 per year x 2 national average compensation overhead = $5,400,000 per year per floor of workers No Productivity Savings

Assume Worker Salary increase of 5% yearly

year 1 2 3 4 5 6 7 8 9 10

base + 5% increase $ 5,400,000.00 $ 5,670,000.00 $ 5,953,500.00 $ 6,251,175.00 $ 6,563,733.75 $ 6,891,920.44 $ 7,236,516.46 $ 7,598,342.28 $ 7,978,259.40 $ 8,377,172.37

no difference 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

NO productivity savings $ $ $ $ $ $ $ $ $ $

Double Skin Glass Faรงades

$ $ $ $ $

Total Green Premium

(13,131.50)

Summary of Energy Savings & income over time yearly energy savings yearly increased rental income yearly additional cleaning costs yearly increase productivity savings

= = = =

$ $ $ $

1,289.90 2,400.00 (900.00) -

Total Savings yearly = (first year, before energy rate and worker comp increase)

2,789.90

(41,875.00) (1,875.00) 1,875.00 6,250.00 22,493.50

Note: Energy prices increase 5% yearly Worker salary increases 5% yearly Rental income same for 10 years Cleaning and maintenance same for 10 years

Double Skin Glass Faรงades

$ $ $ $ $ $ $ $ $ $

difference 1,289.90 1,354.40 1,422.12 1,493.23 1,567.89 1,646.28 1,728.59 1,815.02 1,905.78 2,001.06

Energy Savings based on 10% energy increase per year Year Base 20% reduction 1 $ 6,449.52 $ 5,159.62 2 $ 7,094.47 $ 5,675.58 3 $ 7,803.92 $ 6,243.14 4 $ 8,584.31 $ 6,867.45 5 $ 9,442.74 $ 7,554.19 6 $ 10,387.02 $ 8,309.61 7 $ 11,425.72 $ 9,140.57 8 $ 12,568.29 $ 10,054.63 9 $ 13,825.12 $ 11,060.10 10 $ 15,207.63 $ 12,166.10

$ $ $ $ $ $ $ $ $ $

difference 1,289.90 1,418.89 1,560.78 1,716.86 1,888.55 2,077.40 2,285.14 2,513.66 2,765.02 3,041.53

Double Skin Glass Faรงades

Yearly Increases Energy Savings based on 5% energy increase per year year 1 2 3 4 5 6 7 8 9 10

energy savings $ 1,289.90 $ 1,354.40 $ 1,422.11 $ 1,493.22 $ 1,567.88 $ 1,646.28 $ 1,728.59 $ 1,815.02 $ 1,905.77 $ 2,001.06

additional rent $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00

maintenance $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00)

productivity savings $ $ $ $ $ $ $ $ $ $ -

Total savings $ 2,789.90 $ 2,854.40 $ 2,922.11 $ 2,993.22 $ 3,067.88 $ 3,146.28 $ 3,228.59 $ 3,315.02 $ 3,405.77 $ 3,501.06

productivity savings $ $ $ $ $ $ $ $ $ $ -

Total savings $ 2,789.90 $ 2,918.89 $ 3,060.78 $ 3,216.86 $ 3,388.54 $ 3,577.40 $ 3,785.14 $ 4,013.65 $ 4,265.02 $ 4,541.52

Energy Savings based on 10% energy increase per year year 1 2 3 4 5 6 7 8 9 10

energy savings $ 1,289.90 $ 1,418.89 $ 1,560.78 $ 1,716.86 $ 1,888.54 $ 2,077.40 $ 2,285.14 $ 2,513.65 $ 2,765.02 $ 3,041.52

additional rent $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00 $ 2,400.00

maintenance $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00) $ (900.00)

NPV = Value + (valuesi / 1+ratei)i

Double Skin Glass Faรงades

Net Present Value calculated with No productivity savings

Cost of CAPITAL @ 5% energy increase per year Interest Rate 0% 5% 10% $ (10,474.45) $ (10,595.23) 1 $ (10,341.60) $ (7,885.43) $ (8,236.22) 2 $ (7,487.21) $ (5,361.20) $ (6,040.80) 3 $ (4,565.09) $ (2,898.67) $ (3,996.39) 4 $ (1,571.87) 1,496.01 $ (494.90) $ (2,091.47) 5 $ 4,642.29 $ 1,852.90 $ (315.48) 6 $ $ 7,870.88 $ 4,147.39 $ 1,341.30 7 $ 6,391.13 $ 2,887.78 8 $ 11,185.90 $ 8,586.52 $ 4,332.15 9 $ 14,591.67 $ 10,735.86 $ 5,681.96 10 $ 18,092.72 ROI in 5th, 6th & 7th year YEARS

Cost of CAPITAL @ 10% energy increase per year YEARS Interest Rate 0% 5% 10% $ (10,474.45) $ (10,595.23) 1 $ (10,341.60) $ (7,826.93) $ (8,182.92) 2 $ (7,422.71) $ (5,182.92) $ (5,883.31) 3 $ (4,361.93) $ (2,536.40) $ (3,686.16) 4 $ (1,145.07) 2,243.47 $ 118.61 $ (1,582.14) 5 $ 5,820.87 $ 2,788.12 $ 437.21 6 $ 9,606.00 $ 5,478.15 $ 2,379.58 7 $ $ 8,194.74 $ 4,251.98 8 $ 13,619.65 $ 10,944.01 $ 6,060.76 9 $ 17,884.67 $ 13,732.11 $ 7,811.71 10 $ 22,426.18 ROI in 5th & 6th year

Double Skin Glass Faรงades

NPV @ 5% Energy Increase Yearly & No Productivity Savings

ROI

0% 5% ```

10%

YEARS

NPV @ 10% Energy Increase Yearly & No Productivity Savings

ROI

0% 5% 10%

YEARS

Double Skin Glass Faรงades

PART 5: Conclusions US Market Acceptance Double skin glass façades can be a value added feature for high performance buildings provided they can be proven to reduce energy costs substantially enough to warrant their extra expense over standard curtain walls. They have yet to become a commonly used strategy in buildings in the United States. Based on my research, I can make an informed guess that the reasons behind the slow acceptance of double skin glass facades in the US market are attributed to the high initial costs, lack of stricter energy codes, access to relevant historic performance data and a bias in favor of immediate less expensive solutions. Double skin glass façades can become more commonly used in the United States provided these issues be addressed. I have already documented considerable knowledge about the building science of double skin glass façades that indicates there is value. In terms of government legislation, the question is, should stricter energy efficient codes be forced upon architects and engineers to develop buildings that adhere to tighter energy codes or to LEED ratings for example? Will ethical beliefs be sufficient? For the present, a debate on the legislative level in support of implementing and absorbing higher up front costs of technology such as double skin glass façades would have considerable merit. In addition, there is a need to develop production and installation methodology that reduces the cost of double skin glass façades in general. In my research, I found one reference to a mass customized double skin glass façade, by a German manufacturer. Lastly, since intelligent building design is integral to the success of double skin glass façades, it is imperative that this building envelope system be considered only a part of a comprehensive design decision that includes all other facets of sustainable building design. For double skin façades to be acceptable and made viable for the American market, methods affecting and affected by the production and assembly process need to be developed. Emphasizing natural ventilation in low to mid-rise buildings is a long term investment as shown in my net present value exercise, as much as six years. This exercise was not comprehensive, nor was it intended to be so, and further detailing of costs may uncover other factors not considered. In order for small to mid size developers to buy into greener building technology practices, a percentage of return on investment ratio within 3 to 5 years is usually the norm. A study conducted by Greg Kats of Capital E has identified 28 buildings that have achieved LEED Certification or better and has compared them to non-rated buildings. The results showed that some 30% to 70% energy saving of investment costs in green building practices over a 3-year period is possible.16 I have not investigated these claims, nor have I found validated contradictory evidence; therefore, the percentages provided should be taken lightly until verified. Double skin glass façades have a number of financial pros and cons, a primary con being the initial high cost compared to traditional single skin curtain walls. As indicated in Part 4, the initial construction costs though can be justified when compared to energy savings over time. Government sponsored programs that can make it easier for reducing fossil fuel consumption can also be beneficial to building owners. Not all applications of double skin façades are cost effective. Depending on the building technology used, recovering the cost of additional curtain wall skin may be a tricky matter. In most cases, where poor insulation and low energy efficient means are compared against double skin glass façades, it may seem

Double Skin Glass Façades

practical. As compared to less efficient design methods and the factor of rising energy prices mentioned earlier, cost savings can be significant.17 Key factors to consider include the cost of an additional glass curtain wall, additional maintenance costs, additional design services and possibly additional customized components depending on detailing. The most cost effective use of a double skin glass façade is when natural ventilation is introduced and utilized to its maximum capability. This will cut the use of mechanical HVAC system load, thereby reducing the dependence on electricity. It is easy to see the draw to double skin façades. Through trial and error, modeling software and almost 20 years of historic data, we have learned that they can be used successfully to achieve high performance vertical enclosures. Integrated with advanced mechanical systems, building life cycle costs savings could offset any initial higher than normal costs of construction.

Design and Production Concurrent engineering is a design process that employees interdisciplinary teams from the very beginning of a project to ensure that multiple experts weigh in concurrently and coordinate ideas. When multiple disciplines exchange ideas and detect problems early on, unnecessary or redundant engineering time and expense can be avoided later on. Technologically, engineering problems of airflow, moisture control, thermal control and air barrier have been investigated and addressed successfully in numerous projects. Building systems integration, high performance-building concepts, and economic factors associated with mechanical versus passive environmental control systems as broadly outlined in various case studies in European and US markets show a wealth of success for double skin glass façades. As it stands now, economic factors for massproduced systematized components and mass customization techniques in relation to prevailing practices in the US offers manufacturers an opportunity to reconsider building envelopes. This allows an opportunity to rethink the curtain wall industry’s potential in the marketplace. Nevertheless, it appears that unless the cost of producing and installing a double skin façade is considerably reduced, without deteriorating the quality of material and installation, it will be difficult to build in this manner. “The challenge is to reduce the thermal loads to the point where the winter solar gains and annual daylight benefits exceed the losses, thus erasing the current impacts and making the facades ‘energy neutral’”18. At present, individual curtain walls are developed by the frame manufacturer and the logistics of a systematized double skin glass façade falls upon the architectural and engineering team to design. There is as of yet, no off the shelf, systematized components that comprise the double skin façade as an integral system developed and marketed by a single product manufacturer. A proposed solution is the production and assembly of a unitized mass customized system, designed with respect for the US market. Based on what I have learned, I believe that it remains in this realm of the cost effective mass customized solution to help boost their acceptance.

Double Skin Glass Façades

Notes: 1

For more information on St. Gobain’s testing of Le Corbusier’s mur neutralisant and his reaction, see Reyner Banham, The Architecture of the Well-tempered Environment, 1969, p. 161 2 Ibid., Banham, an excellent critical essay that explores the disadvantages of growing popularity of mechanical equipment over more natural passive design objectives in buildings across America. 3 Erwin Panofsky, Abbot Suger on the Abbey Church of St.-Denis and its Art Treasures, Princeton University Press, 2nd Ed, 1979 4 Schittich, Staib, Balkow, Schuler, Sobek, Glass Construction Manual, p. 14 5 William McDonough, Sim Van der Ryn, Bob Birkebile, Pliny Fisk, and Jason McLennan are but a few names to look up as people who have contributed to the sustainable building design movement, of course, there are countless others. 6 James Wines, Green Architecture, Taschen, 2000, p. 38 7 By fossil fuel, I refer primarily to oil, coal and natural gas 8 U.S. Environmental Protection Agency, U.S. Department of Energy, Energy Star 9 U. S. Census Bureau 10 U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology report #NISTIR 7062, “Impact of Natural Ventilation Strategies and Design Issues for California Applications, including Input to ASHRAE Standard 62 and California Title 24”, October 2003 11 Oesterle, Lieb, Lutz, Huesler, Double-Skin Façades, Prestel Verlag, 2001, p. 178 12 Ibid., U.S. Department of Commerce, report #NISTIR 7062 13 Ibid., See Oesterle, p. 114 for illustrations and a description of pressure and suction of air flow around the plans of tall buildings of different shapes 14 Oesterle, et. al., Double-Skin Facades, Integrated Planning, Prestel, 2001, p. 15 Ibid., p. 41 16 U.S. Green Building Council, 2005, based on Greg Kats’ study of the cost of building Green, 2005 17 Ibid., Oesterle, p27 18 Eleanor S. Lee, Lawrence Berkeley National Laboratory, research conducted on Advanced Interactive Facades, Nov. 2003

Double Skin Glass Façades

Double Skin Glass Faรงades

Appendix A: Case Studies As part of this thesis, three buildings utilizing double skin glass façades have been chosen as case studies. These buildings exhibit a successful implementation of the double skin façade technology. GSW Headquarters by Sauerbruch Hutton Architekten in Berlin, Levine Hall by Kieren Timberlake Architects at the University of Pennsylvania and the soon to be completed Center of Excellence by Toshiko Mori Architects in Syracuse, NY.

GSW Headquarters GSW Headquarters, Berlin, Germany, Sauerbruch Hutton Architekten, 1995 – 1999 Features: CFD software determined shape of high-rise, wind used as natural ventilation, thermal mass of floors used in winter, shades manually operated by individuals in summer to control heat gain. All windows are operable on double skin west façade, louvers operable on east façade for controlling cross ventilation for fresh air. In this building design, western prevailing winds are used to draw air through the building via a full height, twenty-two story double skin glass façade. Vertical air movement through the interstitial space relies on the stack effect and a cleverly designed wind foil at the roof of the building. See the chapter titled Thermal Strategy for more information on stack effect. Air that enters from the bottom of the curtain wall cavity is drawn upwards by convection. The wind foil on the roof is essentially an upside down airplane wing positioned above the top most cavity vents creating a positive pressure zone assisting in drawing the air the entire height of the structure. The building was designed on a narrow floor plate in order to take advantage of the prevailing winds for use in cross ventilating the office spaces during warm summer months, alleviating the need for excessive use of mechanical equipment. As illustrated in Figure 74, westerly winds driving into the concaved side of the curved shaped tower create a positive air pressure system drawing air from the east side of the building. The east wall is designed as a double skin façade as well but with operable louvered vents to allow for the cross ventilation. Interior partitions also have integrated louvered vents in order to maintain a continuous path for air flow from one side of the building to the other.

Figure 69 GSW West Façade Detail

Double Skin Glass Façades

Section detail of the west wall showing the double skin glass faรงade and shading device within the interstitial space that can be controlled manually as well as mechanically

Figure 70 GSW Plan Complex illustrating key strategies used in the tower portion of the design

Double Skin Glass Faรงades

Figure 71 GSW Elevation Tower elevation with wind patterns & the wind roof that assists the uplift of air through the tall cavity

Figure 72 GSW Tower Cross Section Cross section illustrating natural ventilation strategy with the double skin glass faรงade on the right

Figure 73 GSW Diagrammatic studies

Double Skin Glass Faรงades

Analysis of building showing how wind foil roof creates pressure zones to draw air through the twenty-two story faรงade cavity

Figure 74 GSW Building Section Designed to take advantage of prevailing winds for natural ventilation, the west wall is a fully glazed double skin glass faรงade, while the east wall is a louvered double skin faรงade with operable louvers to allow for natural cross ventilation

Double Skin Glass Faรงades

Levine Hall Melvin J. and Claire Levine Hall, University of Pennsylvania School of Engineering & Applied Science, Kieren Timberlake Architects, 2006 Features: East and West wall double skin glass faรงades, cavities treated as return air plenum only, cavity is only a few inches deep, components were mass customized and built offsite to specific tolerances to keep costs down, interior windows use bristles instead of sealants to allow free air flow to cavity space.

Figure 75 Levine Hall Massing 3D model of Levine Hall showing how it was designed within a court yard setting

Figure 76 Levine Hall curtain wall concept section

Double Skin Glass Faรงades

Figure 77 Levine Hall curtain wall detail section

Figure 78 Levine Hall winter mode operation

Figure 79 Levine Hall summer mode operation

Double Skin Glass Faรงades

Center of Excellence Syracuse, NY, Toshiko Mori Architects – under construction Feature: The CoE includes a number of sustainable features integrated to support minimal energy usage. Double skin façade on south wall is designed to control air flow and thermal control, at one time an aero gel wall was proposed for the north wall to control sound from nearby highway’s 81 and 690.

Figure 80 CoE, Energy Strategies

Figure 81 CoE, Exhaust Strategy

Double Skin Glass Façades

Figure 82 CoE, South-East Elevation Showing location of double skin glass facade

Figure 83 CoE Floor Plan

Figure 84 CoE Double Skin Glass Faรงade Detail

Double Skin Glass Faรงades

Figure 85 CoE, Winter - Summer Ventilation Strategies

Double Skin Glass Faรงades

Appendix B: Survey A survey was also conducted and found that there are far more examples in Europe of building built with double skin glass façades than in the United States. Two survey maps graphically show approximate numbers, and locations of these buildings in the United States and Europe. At the time that this survey was conducted, the fall of 2006, the total number of buildings found was 112 with only 6 found in the United States.

Figure 86 Survey of Ventilation Modes Illustration showing number of modes found for buildings in the United States, Canada and Europe.

The reason that the numbers don’t necessary correlate with the final building numbers found was due to the fact that there was no mode data was available for some buildings, while others operated on more than one.

Double Skin Glass Façades

Europe, 106 buildings found with double skin glass faรงades

Figure 87 European Map Map showing locations of one hundred and six buildings with double skin faรงades throughout Europe.

Double Skin Glass Faรงades

United States & Canada, 6 buildings found with double skin glass faรงades

Figure 88 US & Canada Map Map showing locations of six buildings with double skin faรงades throughout United States and Canada.

It is interesting to note that all of the buildings were built north of 40 degrees latitude.

Double Skin Glass Faรงades

Bibliography & Reference Glass & Glazing Alan J. Brookes, Cladding of Buildings, (Spon, 1998) Sophia and Stefan Behling (Eds.), Glass, Structure, and Technology in Architecture, (Prestel, 1999) Andrea Compagno, Intelligent Glass Facades: Material, Practice, Design, (Birkhäuser, 2002) Michael J. Crosbie, Curtain Walls: Recent Developments by Cesar Pelli & Associates, (Birkhäuser, 2005) Hugh Dutton, Structural Glass, (Taylor & Francis, 1996) Thomas Herzog, Façade Construction Manual, (Birkhäuser, 2004) Dirk U. Hindrichs, Winfried Heusler (Eds.), Facades – Building envelopes for the 21st Century, (Birkhäuser, 2004) Frank Kaltenbach, Detail Practice: Translucent Material: Glass, Synthetic Materials, Metal, (Birkhäuser, 2004) Heinz W. Krewinkel, Glass Buildings: Material Structure and Detail, (Birkhäuser, 1998) Patrick Loughran, Falling Glass, (Birkhäuser Verlag, 2003) Oesterle, Lieb, Lutz, Heusler, Double-Skin Facades, Integrated Planning, (Prestel, 2001) Peter Rice, Structural Glass, (Spon Press, 2005) Werner Sobek, Glass Construction Manual, (Birkhäuser, 1999) Christian Schittich (Ed.), Building Skins, Concepts, Layers, Materials, (Birkhäuser Edition Detail, 2001) Christian Schittich (Ed.), In Detail: Solar Architecture, (Birkhäuser, 2003) Schittich, Staib, Balkow, Schuler, Sobek, Glass Construction Manual, (Birkhäuser, 1999) Catherine Slessor, John Linden, Eco-Tech: Sustainable Architecture and High Technology, (Thames & Hudson, 1997) Michael Wigginton, Jude Harris, Intelligent Skins, (Architectural Press, 2002)

Sustainability & Green Edward Allen, Fundamentals of Building Construction: Materials and Methods, (John Wiley & Sons, 3rd edition, 1998) Reyner Banham, Theory & Design in the First Machine Age, (The Architectural Press, 1983 Reyner Banham, The Architecture of the Well-Tempered Environment, (The Architectural Press, 1969) Janine M. Benyus, Biomimicry, Innovation Inspired by Nature, (William Morrow & Co., 1997) Peter Blake, God’s Own Junkyard, (Holt, Rinehart & Winston, 1964) G.Z. Brown, Mark DeKay, Sun, Wind & Light, (John Wiley & Sons Inc., 2001) Rachel Carson, Silent Spring, (Houghton and Mifflin, 1962) Norman Crowe, Nature and the Idea of a Man Made World, (MIT Press, 1997) Klaus Daniels, The Technology of Ecological Building, Basic Principles and Measures, Examples and Ideas, (Princeton Architectural Press, 1997) Kenneth Frampton, Studies in Tectonic Culture, (The MIT Press, 1995) David Gissen (Ed.), Big & Green, Toward Sustainable Architecture in the 21st Century, (Princeton Architectural Press, 2003) Al Gore, Earth in the Balance: Ecology and the Human Spirit (Rodale Books 2006) Peter Hall, Urban Future 21: A global Agenda for 21st Century Cities, (Routledge, 2000) Karsten Harries, The Ethical Function of Architecture, (MIT Press, 1998) Paul Hawken, The Ecology of Commerce, A Declaration of Sustainability, (Harper Business, 1993) Philip Jodidio, Architecture Now, Vols. 1 & 2, (Taschen, 2002, 2005) David Lloyd Jones, Architecture and the Environment, Bioclimatic Building Design, (Laurence King Publishing, London) Norbert Lechner, Heating, Cooling, Lighting; Design Methods for Architects, (John Wiley & Sons Inc., 2001) James Lovelock, GAIA: A New Look at Life On Earth, (Oxford University Press, 2000)

Double Skin Glass Façades

William McDonough, Cradle to Cradle: Remaking the Way We Make Things, (North Point Press, 2002) Ian L. McHarg, Design with Nature, (The Falcon Press, 1969, 1971) Jason F. Mclennan, The Philosophy of Sustainable Design, (Ecotone LLC, 2004) Eugene P. Odum, Ecology: The link Between the Natural and the Social Sciences, (Holt Reinehart and Winston, 1963, 1975) Amos Rapoport, House Form and Culture, (Prentice Hall, Inc., 1969) Amos Rapoport, The Meaning of the Built Environment, (The University of Arizona Press, 1990) Bernard Rudofsky, Architecture Without Architects, (Museum of Modern Art, 1964) Sim Van Der Ryn, Ecological Design, (Island Press, 1995) Christian Schittich (Ed.), In Detail: High-Density Housing, Concepts Planning Construction, (Birkhäuser, 2004) H. Leslie Simmons, Harold B. Olin, Construction Principles, Materials, and Methods, (John Wiley & Sons, 2001) James Steele, Sustainable Architecture, Principles, Paradigms, and Case Studies, (McGraw-Hill, 1997) David Suzuki, The Sacred Balance: Rediscovering our Place in Nature, (Prometheus Books, 1998) Steven V. Szokolay, Introduction to Architectural Science: The Basis of Sustainable Design, (Architectural Press, 2004, 2005) Various Authors, Details in Architecture Vols. 1 through 6, (The Images Publishing Group Pty Ltd) Terry Williamson, Antony Radford, Helen Bennetts, Understanding Sustainable Architecture, (Spon Press, 2003) James Wines, Green Architecture, (Taschen, 2000)

Monographs Peter Buchanon, Renzo Piano, Renzo Piano Workshop Vols. 1 though 4, (Phaidon Press) Massimo Dini, Renzo Piano, Projects and buildings 1964-1983, (Electa Rizzoli, 1984) Norman Foster Works Vols. 1 through 4 Joachim Krausse, Claude Lichtenstein, Your Private Sky R. Buckminster Fuller, The Art of Design Science, (Lars Muller Publishers, 2001) Nicholas Grimshaw: Colin Amery, Architecture, Industry and Innovation: Early Work of Nicholas Grimshaw & Partners, (Phaidon, 1995) Nicholas Grimshaw, Structure, Space and Skin: The Work of Nicholas Grimshaw & Partners, (Phaidon 1993) Hugh Pearman, Equilibrium: The Work of Nicholas Grimshaw & Partners, (Phaidon Press, 2000) Jayne Merkel, Eero Saarinen, (Phaidon, 2005) Antonio Roman, Eero Saarinen, An Architecture of Multiplicity, (Laurence King, Princeton Architectural Press, 2002) Roman Moore (Ed.), Structure, Space and Skin: The work of Nicholas Grimshaw & Partners, (Phaidon Press, 1993) Martin Pawley, Norman Foster A Global Architecture, (Universe Publishing, 1999) Renzo Piano, Renzo Piano: Logbook, (Monacelli Press, 1997) Malcolm Quantrill, The Norman Foster Studio: Consistency through diversity, (E&FP Spon, 1999) Franz Schulze, Mies Van Der Rohe: A Critical Biography, (Univ. of Chicago Press, 1985) James Steele, Pierre Koenig, (Phaidon Press, 2002)

Articles and published papers John Gonchar, Peter Reina, Glass Façades Go Beyond Skin Deep, (ENR, 2/10/03) Jan Hensen, PhD, Martin Bartak, MSc, Frantisek Drkal, PhD, Modeling and Simulation of a Double-Skin Façade System, (Eindhoven University) Barbara Knecht and Sara Hart, Commercial Buildings Open Their Windows, (Architectural Record, September 2005)

Double Skin Glass Façades

Werner Lang and Thomas Herzog, Using multiple glass skins to clad buildings, (Architectural Record, July 2002) Stephen Selkowitz, Øyvind Aschehoug, Eleanor S. Lee, Advanced Interactive Façades – Critical Elements for Future Green Buildings? (Presented at GreenBuild, USGBC Conference and Expo, Nov. 2003) C.C. Sullivan, High Performance Building Envelopes: Double Whammy, (Environmental Design and Construction Magazine, May 2006) X. Loncour, A. Deneyer, M. Blasco, G. Flamant, P. Wouters, Ventilated Double Façades, Classification & Illustration of Façade Concepts, (Belgian Building Research Institute, October 2004)

Web Sites http://gaia.lbl.gov/hpbf/backgr.htm High Performance Commercial Building Façades, Building Technologies Program, Environmental Energy Technologies Division Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley http://www.glassonweb.com/articles/article/72/ Glass on Web, Architecture, Double Skin Façades http://www.battlemccarthy.com/Double%20Skin%20Website/index.htm Research, performed by Franklin Andrews, Professor Michael Wigginton of the University of Plymouth and Battle McCarthy, on behalf of the United Kingdom Department of Environment, Transport and Regions http://www.eere.energy.gov/buildings US Department of Energy, Energy Efficiency and Renewable Technology

Double Skin Glass Façades

Biographical Data Name of Author: Place of Birth: Date of Birth: Undergraduate: Degree Awarded:

Anthony M. Catsimatides New York, NY August 23, 1960 Pratt Institute, School of Architecture B. Arch

Professional Experience: Licensed architect in several states, currently practicing in California and New York. Founded “The Open Atelier” in 2002, an architecture planning and design firm designing residential and commercial projects. Presently conducting research into architecture and building technology in a Post Professional Graduate program at Syracuse University School of Architecture. Author of several articles on architecture, modernism, architectural design and architecture of the recent past. In 1995, founded Plan Net Professional Online Service, a technology and web based magazine of resources, ideas and articles about architecture and urban design. Interests include continued studies in architecture theory and communication, and practical applications of architectural technology for housing, communities, and urban design. An accomplished classical pianist, performed works by Beethoven, Bach, Chopin, Debussy, Medner and others.

Summary of Qualifications: Custom high-end residential, multi family, commercial, tenant improvement and retail planning & design. Experienced in all phases of design, building and construction including schematic design, design development, construction documentation, and construction administration.

Architecture / Design Firms: o o o o o o o o o o o o o o o

The Open Atelier for Technology & Design, Architects, San Rafael, CA Michael Rex Associates, Architects, Sausalito, CA Freebairn-Smith & Crane Architects & Planners, San Francisco, CA Gazoontite.com, Retail Planning, San Francisco, CA Plan Net Professional Online, Architectural Web Magazine, Sausalito, CA Interim Technology, Software design and testing, San Francisco, CA Autodesk, CAD software design, San Rafael, CA Levy Design Partners, Architects, San Francisco, CA Barnhart Associates Architects, San Francisco, CA ELS Elbasani & Logan, Architects, Berkeley, CA Glass Associates, Architects, Oakland, CA Acheson Thornton Doyle Architects, New York, NY Arnold Ward Studios, Retail Planning & Design, New Hyde Park, NY J.N. Pease Associates Architects, Charlotte, NC Frank C. Cockinos, & Associates, Professional Engineers, Charlotte, NC

Double Skin Glass Façades

Partial Project List: o o o o o o o o o o o o o o o o o o o

Castro-Allen Housing Project, San Rafael, CA, multi unit housing, single family condominium. Miller Avenue Mixed Use Housing Project, Mill Valley, CA, Multi Family Residential & Commercial New Design & Construction Numerous Single Family Custom residential new construction and remodels throughout Northern CA, New York and New Jersey. Marin Hardwood Floors, Kentfield, CA, Commercial Remodel Tam Junction Redevelopment, Mill Valley, CA, Mixed Use planning & TI G Street Rentals, San Rafael, CA, Multi family residential remodel All Terrain Engineering, Richmond, CA, New Office Building Terminal Plaza Associates, 450 Mission Street, San Francisco, CA, High tech TI Pacific Bell, San Ramon, CA, Corporate TI Epicenter Communications, Sausalito, CA, Office TI Autodesk, Inc., San Rafael, CA, CAD Technology Carnegie Council on Ethics and International Affairs, New York, NY, Office Remodel and New Auditorium Addition Telstar Video Editing Studios, New York, NY, Video Editing Studio Remodel The Towers, New York, NY, Mixed Use Commercial & Hospitality Complex Charlotte/Mecklenberg County Government, Charlotte, NC, New Office Building Duke Power, Charlotte, NC, New Corporate & Technology Facility Underwriters Laboratories, Research Triangle Park, NC, New Office Building Camp Lejeune barracks design and planning, Camp Lejeune, NC Onslow County Correctional Facilities, Onslow County NC, Jail Remodel

Double Skin Glass Faรงades