Arquitectura

An Introduction to Green Building
Part 2: Environmental Sensitivity with Building Materials
By Alexis Karolides, AIA

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ike most animal species, humans have long crafted their environments with collected, nontoxic, easily manufactured, and naturally recycling materials. Then along came the Industrial Revolution, and suddenly we began using the most intense energy source yet known: theplants and animals buried beneath the earth’s surface as fossil fuels. We learned to manufacture useful materials, like steel and plastic, and we could transport them around the world. The seemingly endless

supply of fossil fuels and the environment’s ability to absorb the toxic byproducts of burning them seemed to ignore the simple, evolutionary rules followed by all other animal species: localsupply, low energy, non-toxicity, recyclability. And this ignorance is a problem. First, a stored resource is like a savings account, and the United States’ account of fossil fuel reserves—once seemingly endless—is dwindling. Second, the earth’s ability to assimilate the toxic and slow-to-degrade byproducts of human manufacturing is no

longer guaranteed—all of the earth’s major life supportsystems are either stressed or in decline. Finally, our own products are making us sick—they are made with chemicals that our bodies cannot process. Worse, we have made our buildings nearly airtight, and we are spending 90 percent of our time indoors. So how do we pick the right products to make our buildings more environmentally sensitive? We can start by specifying materials that don’t release largequantities of volatile organic compounds (VOCs) or contain other harmful substances. Instead, specify low-VOC paints, adhesives, and millwork, as well as low-mercury lamps. Minimize porous surfaces upon which mold might thrive (for example, if tile is used, seal the grout), and carefully detail building assemblies to avoid condensation. Finally, if possible, eliminate finish materials, such asceiling tile or carpet, altogether. If carpet is to be used, modular carpeting (carpet tile) is recommended because only tiles in the wear pattern need frequent replacement. Recyclable carpet further enhances waste reduction and raw materials savings. Purchasing local products reduces transportation and its associated energy consumption and pollution, supports the local economy and culture, andmaintains regional identity by promoting the use of indigenous and traditional materials. A more technical way of evaluating a material is to consider its embodied energy—the energy required to produce it. Estimated embodied energy of some common materials is listed in the box on the next page.

The Eastgate building in Harare, Zimbabwe. Inspired by passively cooled termite mounds (p. 15), it stayscomfortable without fans or air-conditioners, providing better comfort at lower cost.

Photo: © 2003 Arup

RMISolutions
Spring 2003

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An Introduction to Green Building
The high embodied energy in plastic and aluminum means these products are especially important to recycle— recycling saves most of the energy in certain plastics and 95 percent of the energy in aluminum. Life-cycleassessment, a very involved process, takes a much larger perspective on the comparative impact of material use. It considers a material’s embodied energy as well as its durability, efficiency, reusability/recyclability, and overall environmental impact (in both its extraction and its use). Although there is not enough space here to go into great detail about various materials, I’ll outline someimportant considerations.
Estimated Embodied Energy of Common Building Materials (in MJ/kg)
baled straw = kiln-dried hardwood = cement = float glass = fiberglass = virgin steel = recycled steel = expanded polystyrene = plastic (EPS) = virgin aluminum = recycled aluminum = 0.2 2.0 7.8 15.9 30.3 32.0 10.1 117.0 191.0 8.1

Green Building Blocks
In general, masonry (brick, block, and stone) has very...