URBAN RESERVE _ Integrated Environmental Simulation Abstract In the past few years, the wide acceptance of CAD (Computer Aided Design) softwares has revolutionised the process of building design. They are capable of providing sophisticated technical, visual and quantitative outputs. But these outputs alone do not always lead to a desired result. As we know, buildings often do not perform as well in practice as they do on paper, nor even as measured during commissioning and maintenance operations. This is when the use of environmental simulation programs can prove paramount. It allows architects and engineers to monitor and gauge the impact of contemporary construction systems and energy models operating in buildings during the primary design phase. This helps provide building performance data and optimise resource consumption, thus resulting in a sound and sustainable output. The paper aims to examine the performance and environmental implications of the proposed sustainable design project (The Urban Reserve) in the Leith docks by using the Integrated Environmental Simulation software as a tool. It will primarily look at the optimal thermal comfort that can be achieved within the building which uses locally available materials while utilizing maximum solar gain, natural light and ventilation. It will also investigate the role they play in reducing the energy demand of the building.
Introduction As much challenging as it is to design a building that creates minimum environmental impact, it is equally difficult to design and execute a space that all people can feel comfortable in. A high level of sophistication can still be achieved with the correct approach. Even though these graphs vary, a comfortable and environmentally sound building should aim to address the following: • Maximizing site potential • Optimizing Energy Use • Protecting and conserving water • Use of low impact, locally available materials • Enhancing indoor comfort • Minimizing operational costs
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The building design process starts with zoning and conceptual design phases and ends with the final design and production of working drawings. It then moves to the construction phase. Once the building is erected on site, the occupants or post occupancy evaluators assess how well the building functions or meets the requirements of its users. Many a times, the predicted performance does not meet the on-site performance of the building. This prompts the need for an intermediate step during the design stage where the energy performance and comfort levels of a building can be predicted. There is a need for an integrated lifecycle energy performance model to provide feedback that can be used to optimize systems’ operation, detect and correct problems for an individual building as well as provide design feedback to improve the design and construction of future buildings. This is when the use of environmental simulation softwares comes into picture. Its use can mean the difference between a good building and a poorly performing one. Whole building design and energy analysis software tools help design professionals analyse the energy performance of their designs. These energy analysis tools help designers understand the implications of design decisions on annual operating costs. Several available software tools have well-developed graphical user interfaces and make intelligent assumptions to assist the user.
Performance feedback provided by whole building energy analysis tools allows designers to provide optimized buildings for their clients. These tools help assure equipment is properly sized for the design conditions of a given building and that the part-load performance of the building subsystems are optimized to provide a comfortable environment with the lowest possible energy costs.
Basic Principles of IES The Integrated Environmental Solution Virtual Environment performance analysis software is a robust energy analysis tool which allows architects and engineers to examine a sustainable design process by offering quantitative feedback on the environmental performance of different design options and complete computationally intensive tasks more quickly and accurately. The simulations aid comparisons between predicted and actual performance of a building thus providing a thorough understanding of how a given building should perform under certain criteria and delivers means to compare and explore different building design alternatives. While doing this, it looks at different attributes of a space like energy performance, thermal comfort for its occupants, natural and artificial lighting, heating and ventilation, systems costs, etc. It can also involve an analysis of the embodied energy within building materials and of methods used to construct 2
buildings. Comparisons are made against standard parameter values used to indicate regulatory requirements, average energy consumption or best practice.
Building geometry comprises of the basic building input for IES simulation. There are differences between building models created by architects and the building models required for energy simulation. In energy simulation models, such spaces are referred not as rooms but as thermal spaces and are defined by space boundaries. The other inputs include weather data of a specific site where the building is located, heating and ventilation loads, internal loads, etc. Apart from these key parameters, finer details like the schedule of openings, type of construction, physical characteristics of materials, space usage, temperature thresholds, etc. fine-tune the results.
Leith Dockyard Leith dock is located to the north of the city of Edinburgh on the southern shores of the Firth of Forth. Formerly a thriving industrial centre and active port, Leith is currently a transitional postindustrial landscape in need of social and environmental remediation. Large flats of land lie unused, some of them reclaimed by nature. The Leith project offers the opportunity to design within social, environmental and economic context of a site that bisects the urban fabric and post-industrial landscape of the Leith dockyards. It is a sparsely vegetated strip of land that stretches from the Leith Ocean Terminal to the casino. A vehicular road runs lengthwise through the middle of the site. While the south side has modern residential blocks, the north face is flanked by water. Like Edinburgh, Leith has a mild temperate climate. Due to the proximity to the sea, the weather experiences minor variations around the year. It’s a windy place with winds predominantly blowing from the South-West direction.
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Weather Data
Program- Urban Reserve The Leith Docks, though located in an urban setting, are rich in biodiversity. A wide range of land, aerial and aquatic species dot the areas in and around the site. The project commences with a thorough understanding of habitats, movement and foraging patterns of three index species dwelling in the Leith Docks. The visual imagery developed from these studies suggests an obscure overlap between these patterns and human activities in the surrounding area. The design proposal intends to define a context of spatial occupation in an urban environment for both man and wildThe Urban Reserve. It aims at creating spaces that act as inhibitors, attractors or even prohibitors to humans and wildlife occupying the site. The site is divided into different zones depending on its present status. Areas with thick undergrowth are marked as the conservation zone while the open parkland falls under the regeneration zone. Areas around Victoria docks become the recreation zone. Belts of physical and attenuation buffers are strategically placed along some of the boundaries of these zones and also along parts of the vehicular road and site periphery. These buffers allow for visual connectivity but restrict physical access to humans. The conservation and regeneration zones, planted with native species of trees and shrubs, over time, will evolve as a rich habitat for the multitude of species thriving in the docks. Eco-pathways snake around the site at different levels. These pathways act as viewing outposts and also educate visitors of the diverse species occupation in the dock areas. They connect the two newbuilds situated at the opposite ends of the site. Planned as social and conservational interventions, these buildings host small scale planning, management, monitoring, educational and archiving facilities for the future development of the urban reserve.
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New Built The following part analyses in detail, the new built situated along the western edge of the site. Connecting the busy urban edge near the ocean terminal to the recreation zone near Victoria docks is the main elevated walkway which also acts as an entrance pavilion to the buildings. The program is divided into two free-standing tower blocks connected at the first floor level. Block-1 features a species gallery, a studio space and an archive while block-2 hosts a cafeteria, viewing outpost and a service block. Both the blocks and the entrance pavilion use materials available in the dockyards either in waste or recycled form. For instance, the elevated pathway is flanked by screens made out of pressed wastemetal from the scrapyard while the elevated landscape at the ground level is contained within a waste-concrete gabion wall.
Block 1 Bock-1 is comprised of four levels of functions connected via a common, south-facing atrium. A compact, vertically stacked floor-plate measuring 8.5M x 8.5 M greatly enhances the quality of air and light inside the building. The partition-free internal spaces face the atrium and are connected vertically by an open staircase. The first/ entry level houses a ‘species information gallery’ that flows to the ground floor level. The second level is an archive space while the topmost level is occupied by an open studio cum administration area. A terrace garden covers the flat roof and can be accessed from the top floor level via an external staircase.
Building Analysis The key driving factors for the project are:1) To reduce the embodied energy of the built form by maximum use of materials procured from the dockside. This includes use of waste and recycled materials. The external walls are made out of seaweed insulation (grows profusely along the firth shore) sandwiched between layers of recycled steel panels sourced from the scrapyard and timber slats obtained from the distressed pier from the main dock. This marginally affects the thermal properties of the building envelope as compared to more contemporary materials but at the same time; considerably reduces the embodied energy of the structure. Use of recycled steel members is also extended to the structural framework. 2) Naturally lighting and ventilating the building, while maintaining a comfortable internal environment is the other important criteria. The vertical open space in conjunction with the 5
south-facing, double glazed façade is designed to do just that. Before entering the building, air flows through the cavity in the double façade. High solar gain within this cavity is used to heat the air up and is then circulated within the building. While the double glazed internal façade provides a high level of insulation, the external facade uses photovoltaic glazing which contributes to energy generation. This energy is primarily utilized to cater to the heating loads of the building. The atrium allows ample amounts of natural light to filter into the building thus reducing the energy demand for artificial lighting. It also acts as an exhaust duct for stale air to exit the building through an opening in the skylight.
3) Maximum heat from any object is lost to the ground hence it is important for the ground floor to be well insulated. The ground floor is slightly elevated above the ground level. This gap, while acting as a natural habitat for reptiles and rodents, also prevents heat loss. The green roof forming the top envelope serves a similar purpose.
Space, Materials, Systems and Functional characteristics of the building analysed:• • • • • • • •
The building is divided into five different spaces based on the level. There are four rooms at each level and a common atrium that each of it overlooks. No internal partitions divide the internal space making it one vertical volume. As the building is located in the regeneration zone, it is inactive at night. The active hours are restricted to 08:00 to 17:00 hrs. It needs to be acoustically sound. Also due to the presence of a full height external glazing that gets in direct sunlight, the interiors are entirely clad in timber. It is entirely naturally ventilated. The heating is taken care of by radiators placed at each floor level. Internal floor made out of wooden planks is supported on a network of post-tensioned timber beams. It also features triple-glazed, external windows and narrow skylights on the external façade.
The analysis begins by simulating block-1 in two different architectural conditions. The entire building remains same except for in case-1 the south-facing external facade is singly glazed, while case-2 has a double façade with an open cavity for natural air to flow in.
Case-1
Case-2
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Materials Chart for the Project
Architectural System
External Wall
Materials
• • • • •
Ground Floor
Internal Floor
Roof
• • • • • • • • • • • • • •
External Skin
• • • • • •
Internal Skin
•
External Window Roof light
• • • • •
Thickness Conductivity W/(m.k) (mm)
Density Kg/m3
Specific Heat Capacity J/(kg.K)
Recycled steel cladding Cavity Sea-weed insulation Vapour barrier Internal timber cladding Timber floor Neoprene layer Sea-weed insulation Weather board Concrete layer Metal decking Timber floor Neoprene layer Recycled steel plate Cavity (beams) Acoustic tiles Soil Drainage cavity Waterproofing membrane Concrete layer Metal Decking Sea-weed insulation Cavity Acoustic tiles Photovoltaic laminate glass
5mm
43
7690
418
25mm 250mm
0.04
473
900
20mm
0.14
419
2720
20 07 200 20 100 50
0.14 0.30 0.04 0.14 2.30 160
650 1600 473 650 1200 2800
1200 2000 900 2000 999 896
25 07 05 12.5 12.5
0.14 0.30 43
650 1600 7690
1200 2000 418
0.06
480
2142
250 25 15
0.15
1200
800
0.19
1121
1674
50 50 200 25 12.5
0.38 160 0.04
1200 2800 473
1000 896 900
0.06
480
2142
12
0.06
Triple-glazed internal glass skin Cavity Low emissivity glass Triple glazed window Cavity Low emissivity glass Triple glazed unit Cavity
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0.01
25 6
0.01
12 6
0.01
12
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Room-3 from both types is simulated for ‘internal temperatures’ alongside ‘internal ventilation’ and ‘internal humidity’ around the year. The aim is to compare the performance and choosing one typology to move forward with refining the design further.
Case-1 Case-1: Internal temperature fluctuates from 6* C to 30* C round the year with an average daily variation of 5* C. Natural ventilation is at its peak during the months of August and September and falls during winter. Case-2: Internal temperature fluctuates from 8* C to 26* C round the year with an average daily variation of 4* C. Natural ventilation is at its peak during the months of August and September and falls during winter but a tad less than in case-1.
Case-2
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Case-1 Case-1: Internal humidity fluctuates from 20% to 90% round the year, but close overlaps with the temperature during the winter months could lead to uncomfortable internal space conditions Case-2: Internal humidity fluctuates from 30% to 90% round the year, though it is on the lower side when the temperatures are higher during the summer months and on a relatively higher side during the winter months making it slightly more comfortable than case-1.
Case-2 9
Detailed Thermal Analysis From the above observations, it is clear that case-2 building with a double façade has a superior thermal performance than the case-1. The system can positively affect the way the building behaves in the temperate climate of Leith. Few of the advantages of using the double façade are: • • • • • • •
Avoid overheating the gallery space. Acceptable internal surface temperatures during winter and summer. Improved acoustical performance. Use of natural instead of mechanical ventilation using the double skin façade cavity. Reduction of heating demand during winter. Reduction of peak heating loads. Use of natural daylight instead of artificial as much as possible.
Another important application of the external face of the façade is that it will be fabricated using insulating photovoltaic laminate glass panels. These panels, while allowing solar radiations to filter through, also generate energy. With close to 60 square meters of south-facing area it will considerably cut down on energy costs while reducing the building footprint. The thermal analysis shall commence with simulating the indoor air temperatures. The space template is configured to try and achieve a constant temperature in the range of 18*-23* C throughout the year with maximum natural ventilation and minimum heating requirement. For the thermal analysis ‘Room 2’ (Atrium) and ‘Room 3’ (Entrance) will be used for simulation. Room-2 is a four storied atrium spaces that possesses the south facing double façade, a skylight/ exhaust vent and 3 smaller openings at midlanding level of the staircase. Room-3 faces room-2 and has a south facing entrance door along with a north facing window opening
Room-2 (Atrium)
Room-3 (Gallery Entrance)
We start with analysing the indoor temperature of the entire building throughout the year. The model is simulated with the heating system is switched off to get an idea of how the building envelope performs in different seasons.
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Internal air temperature (all rooms) throughout the year The building temperature throughout the year reaches a maximum of 26* C for a short period of time during the month of August (peak summer) which is slightly above the acceptable limit. From December-February it fluctuates between 12* C- 18* C. It remains more or less constant between 19* C- 22* C for the rest of the year. In the next simulation, we compare rooms 2 and 3 separately for their internal temperatures while activating the radiant heating to better understand the space dynamics.
Internal air temperature vs. Heating loads_Room-2
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Internal air temperature vs. Heating loads_Room-3 In both the cases, the heating loads are substantial during the winter months of December to February. They are much lower in October, November, March and April. As for the rest of the year, (May- September) when the internal temperature is in a comfortable range of 19* C- 23* C, these loads are miniscule. The temperature in room-2 (atrium) is reflected in room-3. Both these spaces are expected to display similar figures as the atrium conditions all the other rooms in the building. The diagram below shows in detail the heating loads in the different rooms throughout the year. Room-2 accounts to 32% of the total heating load.
Natural Ventilation- All rooms throughout the year 12
The next graph looks at the levels of natural ventilation alongside percentage of people dissatisfied.
People dissatisfied vs. Natural ventilation_Room-2
In both the rooms 2 and 3, the results show a whopping 75% dissatisfaction level during the certain days of winter but drops down to an acceptable level during the summer months. Natural ventilation functions effectively during March-November and is at its peak from June- September. It would be fair to conclude that the drop in natural ventilation during the winter months contributes to the higher number of individuals not satisfied with the internal thermal comfort.
People dissatisfied vs. Natural ventilation_Room-2
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In the entire building, the external windows that bring in fresh air have the same macro-flo opening template as shown in the screenshots. They perform effectively from March-November when the outside temperature goes above 10* C. However the lack of effective natural ventilation during the rest of the year prompts the need of employing a mechanical ventilation system. The graph below shows the break-up of fresh air intake from different rooms. The prominent wind direction throughout the year being the South-East, It is clear that Room2 lets in maximum fresh air. The other four rooms contribute 60% to the total intake.
Project External window – MacroFlo opening Configuration + Daily window profile diagrams
Natural Ventilation- All rooms throughout the year 14
The following graph provides information about the building heat gains throughout the year separately for rooms 2 and 3.
Building heat gain throughout the year - Room 2
Both graphs suggest that solar gain has a positive effect on the internal environment during winters. It cuts down heating demand during this period. In summers it is on a higher side but is compensated by natural ventilation as the double faรงade sucks in more fresh air due to buoyancy effect of air. The performance could be further improved by introducing an internal glazing with lower E-value. External conduction also accounts to certain amount of heat loss.
Building heat gain throughout the year - Room 3
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Solar gain throughout the year – All Rooms
Considering the fact that room-2 is an atrium space, the higher solar gain is slowly propagated to other rooms enhancing the comfort especially during winters.
Conclusion From the above observations, we can derive the following conclusions: •
• • • • • • • •
The external envelope uses locally sourced materials and still provides a satisfactory thermal performance. The main positive is that it significantly reduces the embodied energy of the building. Timber cladding on the internal faces means better surfaces temperatures and thus added thermal comfort. Mechanical ventilation could be used during winter months to improve the quality of indoor environment when natural ventilation doesn’t work as predicted. Photovoltaic façade generates substantial amounts of energy to handle heating loads. The same could be used for mechanically ventilating the space during summers. Ample natural lighting reduces reliance on artificial lighting fixtures thus saving energy. High solar gain helps cut down on energy costs, especially during summer. Adjustable solar shading can be introduced in the façade cavity to avoid overheating of space on sunny days. Solar chimney in the main skylight can also help improve the internal air quality by expelling stale air from within the building. A thicker wall insulation clubbed with more sophisticated, low E-value glass for external windows and roof-lights could help prevent heat loss due to conduction.
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Energy Consumption The total energy consumption of the building around the year comes up to 28.9 kWh/m². The factors that substantially help lower the energy use are low heating loads during summer, Natural ventilation of spaces and most importantly- the south facing photovoltaic facade
Carbon Dioxide The CO2 emissions of the building are in the range of 2179 Kgs. The main aim is to reduce it during the lifespan of the building by incorporating intelligent performance strategies. The Urban Reserve uses sustainable design strategies like passive ventilation, maximumm solar gain, energy generation and natural lighting to redue the CO2. Also, locally sourced materials help reduce the embodied energy of the building.
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Natural Light_Room-1 (Ground Floor) 21 June 12:00
Natural Lighting Utilising maximum amount of dayight in a building helps cut downconsiderably on artificial lighting loads. The south facing atrium has a full height, double skin faรงade that acts as the chief source of natural light in the building. The atrium acts as a buffer space between the faรงade and the internal occupied spaces thus avoiding direct sunlight during most of the year. Apart from the faรงade, an overhead skylight above the atrium, two rooflights at the ground and 3rd levels and two north facing windows at the second and fourth level are the chief sources of natural light. The natural lighting analysis diagrams (see next page for floor plans) suggest that on sunny days, during the months of April to August when the solar azimuth is much higher, the building may get excess sunlight/ glare (especially from the south faรงade). This could be avoided by introducing solar shading devices within the faรงade cavity that will not affect the flow of air within. Also, the skylight can have an adjustable louvered screen to block harsh afternoon sun during summers if necessary. Room-2 (Ground Floor) 21 Dec 12:0
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All floor plans showing the intensity of natural light on June 21st and September 21st at 12:00
There is absolutely no doubt that broader use of energy analysis software and sustainable building design procedures among architects will ultimately help them provide more efficient and comfortable buildings. IES VE does exactly that. The software has an easy to understand, user-friendly interface. The template and material libraries are phenomenal and help a lot in giving a better understanding of sustainable approaches. On the other hand, the relation between the model and its attributes is a bit loose. At times the only way out is to model from scratch. Other barriers to the adoption of IES tools include the steep learning curve and the amount of data input required. Typically, energy analysis is an engineering function often associated with energy code compliance, which is why this exercise has helped me gain an extensive insight into the more technical aspect of sustainable design. I would like to further hone my skills with more practice and analysis of a different project.
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