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How green architecture and sustainable design relate to fabric structures.
By Nicholas Goldsmith
For millennia people have worshipped the sun for its warmth, its light and its capability for producing food. In modern times we have come to take the sun for granted. The Earth is solar powered yet we are largely unaware of our dependence on this star.
Early civilizations everywhere turned to the sun and knew its changing angles from its high points at the summer solstice to its lows at the winter solstice. Since the sun was the only power source, all buildings used passive solar design to maintain a balance of heat, cooling and light. Roof angles, overhangs, window and roof apertures were all designed to screen or accept sunlight, especially since most of the early civilizations sprung up near the Equator.
With a new increased awareness in sustainability and local building traditions, we are at a time where architects are merging the dynamic forms of Modern Architecture with local environmental issues, bringing daylighting and shading as elements of a building’s composition.
Architects who design with green and sustainable building methodologies use the LEED process (Leadership in Energy & Environmental Design).* This reference guide affects a project from initial concept through to test results on the energy systems of the completed facility. Besides certain prerequisites, the LEED process gives points to six different areas: sustainable sites (SS), water efficiency (WE), energy & atmosphere (EA), materials & resources (MR), indoor environmental quality (IEQ), and innovation & design (ID). Many of these areas, while critical to the energy use and sustainability of a site, do not directly engage the use of lightweight structures, so I have chosen those areas that could use fabric structures for credits and describe some of their potential applications here.
Five areas that could possibly use lightweight and fabric structures include:
SS Heat Island effect on roofing: Credit 7.2 / 75% of roofing with high emissivity roofing of 0.9 (as per ASTM 408), Single Ply Roofing —1 point.
SS Alternative transportation: Credit 4.3 / Alternative Fuel refueling stations for 3% of total vehicle parking, photovoltaic (PV) parking structure —1 point.
SS Light Pollution: Credit 8 / Fabric shielding of all fixtures create …Design exterior lighting to produce minimal illumination from reflected sources, volumetric lighting**—1 point.
EA Renewable Energy: Credits 2.1, 2.2, 2.3–5 / 15% of building’s total energy use through the use of renewable energy systems, PV thin-film systems—1 to 3 points.
ID Innovation in Design: Credit 1 / Strategies that significant environmental impact and occupant benefits or strategies that exceed the requirements of existing LEED credits, Passive Solar—1 to 4 points
Of these five, the most powerful category is in the Innovation in Design credit. Here architects are encouraged to use innovative sustainable new technologies. By looking at climates around the world, we see there are many distinct climates, each requiring a different environmental building approach. In the U.S., we have approximately five different climates: a wet and cold climate of the Northeast and Midwest, a wet and warm climate of the Southeast (as in Atlanta), a hot and dry climate of the Southwest, a Mediterranean climate of central California and the Rocky Mountain climate of cold wet winters and warm dry summers.
Indigenous architecture dealt with these different climates by developing separate building types: the adobe structures in the Southwest, the shotgun houses of the Southeast, to the insulated wood frame houses of the Northeast, all are examples of these differences.
In lightweight structures, we recommend mesh shade structures for the Southwest, tensile membrane structures for the Southeast, and foil pillow (ETFE) structures for the North and Midwest. Naturally there are other mitigating effects besides climate on buildings, but it is helpful for architects to understand the baseline climate and work from it.
In the Southwest, probably the most well known example of shading using fabric is the Phoenix Central Library by Wil Bruder + DWL. The library is situated on Central Ave. in downtown Phoenix, creating a metaphor for the natural mesas of Arizona. The building’s five floors are in a rectangular grid with 9.1m column bays. The East and West sides contain two service walls or “saddlebags” which go beyond the enclosure of the building and free up library space in the building’s center. On the South side, solar tracking louvers were designed to minimize heat gain, but on the North side Bruder wanted to passively shade the glass curtain wall. Studies showed that low early morning sun would enter from the North and shoot straight into the glass reading room located on the fifth floor.
We developed a series of lightweight aluminum spars which clamped vertical fabric strips from both sides, similar to nautical details, along each mullion of the curtain wall. A total of 25 shading elements, each about 23m long covered the entire North façade. Since the architect wanted views out of the library to remain unobstructed, we recommended using a mesh fabric with 50% openness. This still provided adequate shading but allowed visual sight from the inside out and at night appeared to disappear. This lighting effect is well know in the world of theatrical lighting when you take open scrim and light it from the front, it looks opaque and when you light it from the back it becomes transparent.
The project redefined the concept of a brise-soleil by translating it into a tensile architectural solution. As a result, the building responds to the environment using an age old solution in a dynamic and new interpretation.
This is one of many possibilities of using fabric as a way to control daylighting, improve environmental qualities of your buildings, extend your buildings beyond their enclosed footprint and meet some of the LEED credits in the Innovation in Design category. Another area of great promise for lightweight structures is in the Energy and Atmosphere section for renewable energy systems and Alternative Fuel Refueling Stations in the Site Selection area. Here the use of thin film photovoltaic energy systems laminated onto fabrics can produce 5 W/ft.2 of energy. They can be used as either generating energy for the 5% to 15% of renewable energy or used as refueling stations for electric car vehicles which need to be 3% of the total parking of the site.
We have worked on a few projects using this technology including the first installation of photovoltaics on membrane structures in 1998 at the National Design Museum (“Under the Sun”.)
Finally the area of heat island roofing and light pollution are relatively easy for an architect to meet. They require a light reflective surface which can easily be a tensile membrane or single ply roofing for the former, and fabric shielding for fixtures to create a volumetric low light level.
The LEED credits create opportunities for architects to use fabric elements in their work which can be rewarded as points towards LEED certification.