Research paper - Intelligent Skins

FACULTY OF ARCHITECTURE, MANIPAL UNIVERSITY, MANIPAL DISSERTATION PAPER, OCTOBER (2015-16 )

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INTELLIGENT SKINS GAUTAMI PAUL Semester 7, Section D,Faculty of Architecture , Manipal University ,Manipal ,gautamipaul16@gmail.com

-----------------------------------------------------------------------------------------------------------------------------ABSTRACT The major global environmental problems faced by us in the beginning of twenty-first century is the risk posed by green house effect resulting in impact of climate change .It has been a concern for damaging the fragile ecosystem by increased development and resource extraction to meet the present needs. Buildings are the major burden on environment , they have a key role in significant environmental degradation .

But with the advancement in technology and awareness about the degrading environment has lead the designers to incorporate energy efficient strategies into the buildings and make them more environment friendly .

As a principle element of architecture ,technology advancement has made the wall as a dynamic part of the building .The traditional objectives of wall has been redefined .The research focuses on the emergence of new technologies .Their relevance in Indian context in terms of climate, energy consumption and practical application. The main objective of this research is to control internal environments through a responsive building fabric . And Explores a new approach to Intelligent Buildings, focusing on the fabric of the building responding to external changes and internal demand.The research has been conducted through various research papers , journals and articles on intelligent skins .Few references has been taken by the book 'Intelligent skins ' by Michael Wigginston and Jude Harris .To study about the feasibility of intelligent skins ,many secondary case studies have been referred .

KEY WORDS :Dynamic facades , adaptive skins ------------------------------------------------------------------------------------------------------------------------------1 INTRODUCTION The external walls are referred as 'facades' which has a fundamental function of protection from weather and also interior comfort . Another aspect is its aesthetic feature, need for ornamentation to give building its identity . The building facade mark the transition between outside and inside .Since facades acts as a physical barrier it should understand the need and comfort of its occupants , also to view , lighting, ventilation, solar gains are the tasks which it needs to address. This inability of self-detection and self adjustment lead to the development of building envelopes that would perform under all types of weather conditions . .Building membrane acts as a climatic mediator between climate and occupant . The term “intelligent” and “adaptive” building skins is referred in façade design to describe the building envelopes that enhance the relationship between the built and the natural environment by using design principles inspired by nature. The development of the facade technology involved the creation of

multilayered, lightweight and transparent skins . These characteristics are embodied in the curtain wall facade type, which led to design variations such as the “alternating” facade which combines single-skin and multi-skin facades, and the “integrated” facade equipped with facade systems as decentralized ventilation units. This chapter reviews on the concept of intelligence and how it is applied to the building skin .

2 DEFINITION The 'intelligent skin' is an essential part of the intelligent building, that element which performs the function of enveloping the inner space.Metaphorically ,'intelligent skin', emphasize its similarity with the human epidermis. It is a composition of construction elements confined to the outer, weather-protecting zone of a building, which respond predictably to environmental variations, to maintain a comfortable environment .

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WHY DO WE NEED INTELLIGENT SKIN?  Primary function of a building skin is to protect occupants , to act as a moderator between internal and external conditions .Building skins must 'damp ' the extremes of climate to make the interiors comfortable .  The need for intelligent skin to improve the performance of a building fabric by it capable and reduce the need for imported energy for heating , cooling , lighting and ventilation .  It provides a productive and cost effective built environment through optimization of its four basic components (structures , systems ,services and management ) and the interrelationship between them .  It Maximizes the efficiency of its occupants .Allows effective resource management with minimum life costs .

4 METAPHORS AND MODELS Intelligent skin programme is based on an example ,which is related to the environmental performance of the whole building , and also bears a closer kinship with the biological phenomenon of intelligence and response. While using the term 'intelligence 'for inanimate mechanisms, it is important to understand its metaphorical use .

1. ARTIFICIAL INTELLIGENCE The working of 'intelligent' systems for inanimate mechanisms has lead to the development of 'artificial intelligence '. With this concept objects are provided with the capacity to perform similar functions to that of human behavior , by emulating the thought process of living being . Artificial intelligence has been used to mimic the human tendency to process information through learning , understanding ,making and acting on decisions .

2. NATURAL INTELLIGENCE This intelligence relates to the faculty found in living beings , it is the naturally responsive system , such as thermo regulatory powers of the human skin , season change of coats in mammals , or opening and closing of flowers to sun light etc. Similar comparison of intelligent skins is to the human skin .The sensors installed in the building sense the fire or intruders just

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as our senses detect danger .The circulation or ventilation bears a close relation to our breathing system .

5 SINGLE SKIN FACADES Building skins are one of the major influencing factors on building technical system Various technologies are used to produce high performance building skins in order to reduce energy consumption ,the fundamentals are based on the concepts of solar heat gain , day lighting , ventilation , space conditioning .

5.1 SUNSCREEN SYSTEMS The shading strategies is one of the essential methods to combat undesired solar heat gains, which increases internal temperature . Shading of the facade enhances the human comfort by reducing the warming of interior spaces .There are two type of shading systems : external and internal shading .Internal shading includes angular selective facades which provides solar control on the basis of angle of sun incident to the facade .The main objective is to reflect or block the direct solar radiation .

5.1.1 FIXED EXTERNAL SHADING This type of shading does not need any maintenance by users or any adjustments , it is characterized by the part of the building mass .It is designed using sun path stereo path graphic diagram which detects the different dates and times for blocking and admitting the sun rays within the building .

5.1.1.1 HORIZONTAL SHADING These kind of shading are used in southern facades , where the sun path is at a high level , and casts their shadow most of the time of exposure to direct sun .

5.1.1.2 VERTICAL SHADING Generally used for eastern and western facades , since the sun path is low to make vertical shading more effective than horizontal shading where they have inclination with respect to building facade in order to block sun and admit illumination.

5.1.2 OPERABLE EXTERNAL SHADING These systems are used to control thermal gain , redirect sunlight and reduce sunlight .Operable systems are more flexible since they can be retractable according to outdoor conditions .They are interactive with users and adjustable according to occupants needs.

5.1.2.1 SHUTTERS These are movable wooden or metal coverings , when closed they keep the sunlight out .Shutters can be solid or slatted with fixed or adjustable slats .They also provide security and privacy .It is widely used due to its economical cost and effectiveness .

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5.1.2.2 ROLLER SHUTTERS These shutters are a series of horizontal slats which runs down along the track .They provide good security , many roller shutters can also be controlled from interiors. Its disadvantage is that they block view and light when fully opened 5.1.2.3 LOUVERS They are adjustable slats that control the level of sunlight entering the building .The slats are either vertical or horizontal .Louvers remains fixed to the exterior of the window frame . The louver is approximately 1.97 ft. (60 cm) wide and length may varies from 2.95-5.91 ft. (90180cm) mounted at sloping 45 or 135 degree positions.

5.2 DAYLIGHTING SYSTEMS The use of daylight is important for comfort and contentment of the users and also with regard to reduce demand for artificial light. Day lighting is applied according to room depths and precludes the direct use of daylight , where quality of lighting is main priority.

5.2.1 LIGHT REIRECTING SYSTEM It works on the principle of reflection, diffraction and reflection to enhance the incoming daylight within the building .Improved distribution enhances the lighting quality and visual comfort .

5.2.1.1 SUNLIGHT REDIRECTION Light shelves are horizontal projection that uses high reflectance or semi specular upper surface to reflect incident sunlight .Prismatic aluminum films are used on the upper surface to enhance the reflective optical efficiency , and moveable systems are used to alter the depth of redirection .Between -pane light shelves can be fabricated in volume and protect from dirt and dust between two panes of glass.

5.2.1.2 SKY-LIGHT REDIRECTION This light-redirecting system is designed for climate with cloudy conditions to get diffused skylight . Anidolic system works on the principle of non-imaging optics to collect omnidirectional diffused light and direct flux with mirrored curved geometries. This focused daylight can be then redirected along the ceiling plane and distributed through light ducts .The collector optics are created using plastic injection moulds which then be coated with a high grade aluminum coating

5.3 VENTILATION SYSTEM Natural ventilation is used for reducing energy consumption , as it is cost effective and also provides a healthy and comfortable and productive indoor climate .

5.3.1

VENTILATION CONCEPTS INTEGRATED WITH INTELLIGENT SKINS

5.3.1.1 SINGLE SIDED VENTILATION When windows are at only one side of the room .Cold air streams in , while the warm air streams out through the same window It is helpful for certain room height .

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5.3.1.2 SINGLE SIDED DOUBLE OPENING A development of the single sided principle provides a double opening , which is more efficient.

5.3.1.3 STACK VENTILATION Natural buoyancy of hot air is used for smoke ventilation ,which is allowed to vent through high level vent , replacing fresh air enters through the lower side via double facade . Highly glazed facade , with translucent motorized external glass louvers , operated by building management system .Which can also be overridden by the occupants .To diffuse direct sun light glass louvers can be rotated .Passive stack ventilation system draws the hot air through duct in the wave form structure ,low resistance propellers are attached at the top to provide minimum ventilation and to throw internal heat gains .

6 DOUBLE SKIN FACADE A new trend has been developed by the invasion of multiple skin facade .The spacing the two layers is used for ventilation and other purposes. Various features are integrated with facade to address the specific need : screens , blinds ,louvers operable windows for air to migrate from interiors to exteriors , insulating glass with coatings to reduce transmission loss .The double skin facade consists of two glass skins placed in a way to allow air flow through the cavity ventilation can be natural , mechanical or fan supported. The glass can be single or double glazed placed at a distance of 20cm to 2 meters. These facades also provide acoustic insulation .The construction of facade regulates cold ,heat ,light as well as noise to get optimum comfort and less consumption of energy .

6.1.1

PARTITIONING OF THE FACADE

6.1.1.1 BOX WINDOWS This is the oldest type of two layered facade .I t consists of a frame with inward opening casement .The single glazed exterior skin has opening which allows ingress of fresh air and out flow of vitiated air .The cavity between the two layers is divided horizontally along the constructional axes. Vertically, it is divided either between stories or between individual window elements 6.1.1.2 SHAFT BOX FACADE The concept is based on the twin face which consists of a box window with continuous vertical shaft to create a stack effect . On every floor shaft is connected with opening .The stack effect draws hot air through the box window and take upwards where they are emitted.

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6.1.1.3 CORRIDOR FACADES In these facades the intermediate space is blocked at every floor level .The openings for intake of fresh air and extraction of air is placed near to the ceiling and floor.

6.1.1.4 MULTI STORY FACADE In multistory facade the intermediate space is adjoined vertically and horizontally .These facades are used where the external noise level is very high . The ventilation is carried out by a large opening at the ground floor and at the roof .During summers , the facade space can be closed for optimizing solar energy gains .Facade can ne joint and used as a air joint duct , which needs to be ventilated mechanically .

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ENERGY PERFORMANCE AND COMPARATIVE ANALYSIS OF TRADITIONAL AND INTELLIGENT FACADE This is a study between two buildings with masonry wall facade with punched windows, while the other with curtain wall facade .Only one wall is exposed to the exterior and floor to thermal resistance is 0.9 sq.m.K/W . Buildings have been placed in two different climates one is composite with cold winters and warm summers and other is warm and humid climate with cool and humid winters and hot and dry summers .

7.1.1 CASE I The first test is to compare the heating and cooling demand for both the climates , provided that no internal gain is assumed and no lighting and shading systems are used .

COMPARISON As a result transparent facade demands higher amount of heating and cooling , when lighting and shading are not taken into account. Due to increase in solar gain with no shading and also no natural ventilation is used resulted in increase of cooling demand . the annual source energy consumption for building with masonry wall facade is 66.5KWh/m2 for composite climate and 36.1KWh/m2 for warm and humid climate , whereas for building with curtain wall facade it was 106.8KWh/m2 and68.5KWH/m2 respectively .

7.1.2 CASE 2 When internal heat gain is taken into account and basic lighting ,shading and ventilation system is used. South facing building is considered with two occupant load . Installed lighting power density is 12W/m2 for building with masonry wall facade and 9W/m2 for building with curtain wall .Interior roller shades are used for windows . Curtain wall uses reflective shade of 77% reflectance, while 37% for the building with masonry wall facade .

COMPARISON Table 1. Annual heating,cooling,lighting demand The curtain wall results in high heating and cooling demand than the masonry wall but lower lighting demand , which also affects the cooling energy use . Heating gains also increased as occupant load was also considered.Use of lighting system in 6|Page

building with curtain wall facade benefits the daylighting level which helps in total source energy consumption.

masonry facade

curtain wall facade

Composite climate

masonry wall facade

curtain wall facade

Warm and humid climate

The total energy consumption of building with curtain wall is 12% lower than the masonry wall building in composite climate , whereas it is 15% lower in Warm and humid . Using basic lighting and shading systems resulted in reduction in energy consumption .

7.1.3 CASE 3 Earlier study was based on basic lighting ,shading and ventilation devices , in this section advanced system is used to make the facade intelligent .

COMPARISON The curtain wall building results in lower overall source energy use considering all the climates than the masonry wall facade building . Intelligent facade includes advanced solar shading devices which reduces heat gains and optimizes day lighting ,and natural ventilation leading to less load on cooling system. The energy consumption varies in different climates , for composite the energy use is comparatively more than warm and humid for both curtain wall as well as masonry wall building since the heating and cooling requirements are more in warm and humid climate .

Composite climate

Warm and humid climate

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8 CONCLUSION This study compares the energy performance of two buildings, one made up of brick wall, and other with curtain wall construction integrated with intelligent facade. Faรงade design is considered a perimeter zone design, and the aim is to balance the need for day lighting , view, the need of controlling of solar gains and maintaining human comfort, while reducing the energy demand for air-conditioning and lighting. Result shown that the building consumes less energy if equipped with intelligent skin . This study on intelligent skins shows that intelligent faรงades not only provide more natural light and ventilation but also, if properly controlled and integrated with perimeter zones systems, they may result in lower energy use and operational cost compared to traditional faรงade.

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