Setting the stage
Sustainable Space columnist Greg Kallio gives a green building overview
What’s the word?
The adjective “sustainable” is so prevalent and accepted now that it’s easy to lose sight of its intended meaning. One of first times I heard it used (in the 1970s) was in reference to the sustainable yield of forest timber—the idea that the growth rate of our forests should match the rate of harvest. Today, most folks agree with the U.S. Environmental Protection Agency’s broader definition applied to the entire human community that sustainability is “meeting the needs of the present without compromising the ability of future generations to meet their own needs.”
Sustainable (or green) building refers to a building design that maximizes the efficient use of energy, water and material resources while minimizing its negative impact on human health and the environment. A key ingredient to green building is integrated design (understanding how a building works as a system and designing that system to be environmentally friendly).
Sustainable building makes a significant difference in the big picture of energy, water and materials use. According to the U.S. Department of Energy, buildings in the United States account for 39 percent of all primary energy use (energy from raw fuels such as coal, gas, sunlight that is converted or used directly as site energy), 73 percent of all electricity use, 38 percent of all CO2 emissions, 80 percent of all solid-wood forest product use, and 41 percent of all cement/concrete use. Surprisingly, residential buildings have the largest share in each of these categories.
Where do we start in forming an energy-reducing strategy for homes? First, check out the graphic to consider the ranking of primary energy uses in U.S. homes. In California, especially the Chico area, the cooling portion is a bit larger while the heating portion is a bit smaller. Regardless, reducing heating and cooling loads will have the largest beneficial effect. This indicates that the building envelope—walls, windows, roof, floor and foundation—is the most important system of a house to consider in reducing energy use. The next most important consideration is the efficiency of the systems providing heating, cooling, refrigeration and lighting.
Another facet to consider is that the total energy consumption attributed to buildings is due not only to their operation, but also to the manufacture and transport of building materials and the energy used for construction. These additional contributions are collectively known as embodied energy and add significantly to the total building energy budget. This means that a single building material can have multiple impacts on the environment, both negative and positive. For example, a dual-pane, low-emittance window may not be green in terms of its material components or manufacturing process, but if used strategically it can reduce energy use by maximizing the collection of winter sunlight and minimizing summer heat gain.
Bye, for now
Next time I will delve into green-building specifics with an emphasis on energy efficiency and renewable-energy technologies for homes. Stay tuned …