“The Magic Skin” Design Project
Masters Degree, Energy & Environment Program
Architectural Association, London, 2002.
The Masters Program in Energy & Environment studies at the Architectural Association was a unique opportunity to explore Environmental Architecture. The project was a synthesis of the knowledge attained during the course. The environmental theories, techniques, materials, history and analytical tools came together in a project that allowed for pushing the limits of design.
The site is located in the Chiado neighborhood in the old part of Lisbon, Portugal. The area mixes shopping, business, cultural and residential uses and is located on a hill near the River Tejo. Active during the day, the district is one of Lisbon’s livelier night spots.
The program I developed calls for an art center composed of a main gallery, several small galleries, live/work studios for artists, a café/bar as well as open space. The idea is to provide a place where the public can meet the artists and observe them at work. The main gallery will display travelling exhibits in addition to local work. The focus of this project was the overall design concept and the further development of the Main Gallery.
Environmental Architecture starts by evaluating the environmental requirements early in the design process. The main factors of thermal comfort are air temperature, radiant temperature, relative humidity, air movement, clothing and the type of activity engaged in. Lighting is very important in gallery spaces. The amount of light must be carefully controlled to protect sensitive artwork and to provide optimal viewing conditions.
A climatic study evaluates the annual temperature, humidity, winds, rainfall and solar exposure to determine the climate classification. Lisbon ranges from “cool” during late fall, winter and early spring, to “moderate” for most of the rest of the year. The hottest weeks of summer are classified as “warm and dry”. Generally, comfort can be maintained by protecting the occupants from wind and rain during winter and the hot sun in summer.
Based on the climatic conditions and environmental requirements three main strategies were chosen to pursue; thermal mass, effective ventilation and evaporative cooling.
There are several important design considerations other than the environmental strategies to be incorporated into the design solution. The steep site has a predominantly western orientation while a southern orientation is more desirable for solar control. Providing public circulation between the uphill and downhill sides of the site would be a valuable contribution to the urban fabric. There is currently no public green space, though this neighborhood would benefit greatly by its addition. This is a large development for the surrounding neighborhood and must be designed to fit contextually. The site provides excellent views to the south and west and is very dynamic and due to its topography, which is also a design opportunity.
The parti is the basic scheme behind the design. The concept for this project plays on the idea of “blocks tumbling down the hill” and heat rising while cold sinks.
The design process starts by creating a green space on the site. Through faulting action the blocks settle into the contours of the lot in this earthquake prone region. A major circulation route connects the east and west sides of the site while a secondary route runs north-south. Circuitous paths also wind through the site. Next the programmatic elements are integrated into the site.
The Main Gallery is located in the center of the project and is composed of four gallery spaces stepping down the site. Each gallery space is covered on three sides by earth or adjacent buildings, leaving only the South Elevation and roof exposed to the environment. Courtyards act as transitional spaces, allowing light and air into the interior and serving as sculpture gardens. Three zones are encountered moving through the building: Interior, transitional and exterior. These zones are experienced in sequence moving either horizontally or vertically.
The assignment was titled “The Magic Skin” with the intention of a design focus to be on the skin of the building. The development of the Magic Skin begins by looking at skin as a dermatologist would look at it. Skin is composed of many layers with unique functions. Skin reacts to external and internal stimuli. One of the major functions of skin is to regulate the internal temperature. For this project the skin must help to remove excess heat from the spaces as well as retaining heat when required. Controlling the solar radiation and daylight entering the building, two sometimes conflicting tasks, is another important criterion of the skin. It also controls the flow of air through the building, providing fresh air and cooling as needed.
A preliminary environmental assessment at this point reveals the building is fairly close to maintaining acceptable thermal comfort levels without too much intervention. Winter mornings and cold spells will typically require warming of the gallery spaces while summer afternoons will require some cooling. In the Lisbon climate the skin should be able to meet these needs without mechanical assistance. A daylighting analysis demonstrates that without controls the daylighting is non uniform with levels near the openings above optimum art viewing levels but levels further away are well below. The skin must also serve as a daylight harvesting system.
The horizontal skin also has the structure to consider as the largest gallery is over 32 meters squared. The exterior surface is to provide public green space. First, a steel space frame is used to span the gallery. The frame is then set into a form which is then filled half way with concrete. Cylinders are used to form troughs on the surface. Permeable covers are fitted over the troughs creating tubes. The form is then filled with sand and gravel to provide drainage and topped with soil. Grass is then planted in the soil while trees and other plantings needing more depth are planted into boxes set into the roof. Water is then allowed to run through the tubes.
This action provides drainage for rainfall, a concern mostly in winter. During summer the water is pumped to the top and flows by gravity through the skin, free-falling from one level to another. This action cools the concrete mass by extracting heat, creating a cooler radiant ceiling to the gallery below, and thus creating a more comfortable space on hot days. The flowing water also irrigates the vegetation in the green space very efficiently by providing water directly to the roots. The water absorbed by the vegetation is eventually released through transpiration which provides evaporative cooling to the open space. The water is exposed as it drops between levels creating waterfalls elements. This architectural feature provides additional evaporative cooling.
The vertical skin is composed of two main elements; glazing and adjustable louvers. Both of these are supplied in panels 2 meters wide by 3.7 meters tall (ceiling height).
The louvers are dual sided and mounted onto a panel system arranged around posts. One surface is made of a material with high emissivity and high reflectance, designed to reflect solar radiation. The other surface is of low emissivity and low reflectance, designed to absorb solar radiation and release the energy as heat. These surfaces cover an insulating core.
The panels are mounted onto a track system allowing them to move both parallel and perpendicular to the opening they are covering. This allows for greater flexibility in positioning.
Either the glazed or louvered panels can be used alone, the order reversed, or no panels used at all, removing the physical separation between inside and out. The panels can be arranged continuously or staggered. This allows for a great deal of control over lighting as well as air movement for ventilation. Panels can be placed into storage when not in use.
The simple louver system allows for such flexibility that many variations can be achieved with differing environmental properties.
There are two options when the louvers are closed and inside the glazing. Both block the daylight from entering, but the high emissivity side reflects solar radiation while the low emissivity side transforms it into heat energy. A Trombe Wall effect can be simulated using this system.
When the louvers are in the horizontal position most diffuse daylight is admitted into the space. Direct sun is either reflected up into the space or transformed into heat energy and transmitted into the room by convection and radiation, depending on which side of the louver is facing up. The high emissivity side reflects solar radiation while the low emissivity side transforms it into heat energy. A Trombe Wall effect can be simulated using this system.
When the louvers rotated parallel to the sun’s rays they block some diffuse solar radiation while allowing direct solar radiation to enter. Removing the louver panels allows all available solar radiation and daylight to enter. Rotating the louvers perpendicular to the sun’s rays allows limited amounts of diffuse radiation into the space. Direct radiation is either tightly restricted or converted into heat and transmitted inside by convection. The gap between the skin layers in effect becomes a transitional zone, acting as a buffer between inside and out.Combining the many variables in plan and section gives a myriad of possibilities for controlling environmental factors. With a little experience the gallery staff should be able to fine tune each gallery to specific needs at any time of the day or year.
Testing is crucial to be sure the building meets all comfort and performance criteria. Thermal simulations confirm that comfort levels can be maintained at all times with few exceptions. By manipulating the vertical skin the internal temperatures can be fine tuned to acceptable limits.
Natural ventilation is used to provide fresh air and cooling. Incoming air is ducted below grade into each gallery. The earth maintains a constant 17°C (63°F) temperature at this depth. Warm air moving through the ducts is cooled in summer and cold air is warmed in winter. The courtyards help to facilitate ventilation by the stack effect. The warm air in the courtyard rises, drawing the air out of the gallery to replace it. The air in the gallery is then replaced by the ducted air. Simulations show the cooling provided lowers the temperature of the incoming air by 3.5°C (6°F) during the summer. Outdoor air at 28°C (82°F) enters the gallery at 24.5°C (76°F).
Typically daylight is measured as a percentage of outside values to the amount available indoors, known as the daylight factor. But in gallery spaces the actual amount of light falling on an object is much more critical for proper viewing. Initial simulations reveal a non uniform distribution of daylight, leading to glare and visual discomfort (left). The “magic” of the skin can be used to alleviate this problem. By positioning the panels and adjusting the louvers the light can be more uniformly distributed throughout the gallery (right).
The Lisbon Arts Center is a design journey through the process of deriving architectural form from environmental conditions. Evaluating the site, program and environmental conditions leads to a design concept that resolves all of these issues. Further evaluations of building performance are made as the design develops. This is Environmental Architecture.
