Global Impact

There are some issues related to home building and land development that do not fit neatly into the context of the aforementioned guiding principles. For these items that are a by-product of home construction, we have added a separate principle—global impact. One example of an issue having global impact is the selection of paints that contain relatively low or no volatile organic compounds (VOCs). Although the VOC content of paint is often considered for indoor environmental reasons, the vast majority of VOCs are released by the time the paint is dry.  However, the release of VOCs from wet paint helps form ground-level ozone pollution. Therefore, the use of low or no-VOC paints falls under the global impact principle because the environmental impact of using paints with relatively high VOC levels is greater on the global scale than it is on the indoor environment.

Indoor Environmental Quality

Healthy indoor environments attract many people to green building. After energy efficiency, the quality of a home’s indoor air is often cited as the most important feature of green homes. Pam Sessions, president of Hedgewood Properties in Atlanta, said during the 2002 National Green Building Conference that the majority of people interested in green homes in the Atlanta market indicated that indoor air quality was their top issue of interest.  An increase in reported allergies and respiratory ailments and the use of chemicals that can off-gas from building materials have contributed to a heightened awareness of the air we breathe inside our homes. Even though there is no authoritative definition of healthy indoor air, there are measures that can mitigate the effects of potential contaminants including controlling the source, diluting the source, and capturing the source through filtration.

Water Efficiency

The mean per capita indoor daily water use in today’s homes is slightly over 64 gallons. Implementing water conservation measures can reduce usage to fewer than 45 gallons. For this reason, green homes are especially welcomed in areas affected by long- and short-term drought conditions.  The importance of water resources is becoming increasingly recognized, especially in the western third of the country. Choices between sending water to growing urban areas and making water available for irrigation highlight the issues surrounding the scarcity of this valuable resource.  Green homes often conserve water both indoors and out.  More efficient water delivery systems indoors and native and drought-resistant landscaping choices outdoors can help prevent unnecessary waste of valuable water resources.   Communities can obtain additional benefits when builders effectively use native species in landscaping. Current research and practice have shown that natural processes can be a successful means of filtering and removing contaminants from storm water and wastewater.

Resource/Material Efficiency

Most successful green homes started with the consideration of the environment at the design phase—the time at which material selection occurs. Creating resource efficient designs and using resource efficient materials can maximize function while optimizing the use of natural resources. For instance, engineered wood products can help optimize resources by using materials in which more than 50% more of the log is converted into structural lumber than conventional dimensional lumber.  Resource efficiency is also about reducing job-site waste.

Invariably, there are leftover materials from the construction process. Developing and implementing a construction waste management plan helps to reduce the quantity of landfill material. The average single family home in the United States, at 2,320 ft2 (NAHB, 2003), is estimated to generate between 6,960 and 12,064 lbs. of construction waste. Thus, by creating an effective construction waste management plan and taking advantage of available recycling facilities and markets for recyclable materials, construction waste can be reduced by at least two-thirds, creating potential cost savings for builders and reducing the burden on landfill space.  Lastly, basing the selection of building materials on their environmental impact can be tricky. For instance, a product might be renewable, but on the other hand it takes a relatively great amount of energy to transport the product to a project’s job site. One way to compare products is to look at a product’s or a home’s life-cycle environmental impacts through a process called life-cycle analysis (LCA). An LCA of a building product covers its environmental impacts “cradle to grave” through six basic steps:
1) Raw material acquisition, 2) Product manufacturing process, 3) Home building process, 4) Home maintenance and operation, 5) Home demolition, and 6) Product reuse, recycling, or disposal. There are numerous reasons why building products are not commonly selected via LCA’s. One of the issues is the availability of data— there is a lack of data to feed into tools that allow for an LCA on a product or system.

One such tool created by the National Institute of Standards and Technology (NIST) is the Building for Environmental and Economic Sustainability (BEES) software program.  BEES has 10 impact categories: acid rain, ecological toxicity, eutrophication, global warming, human toxicity, indoor air quality, ozone depletion, resource depletion, smog, and solid waste. Since information is not available to conduct full LCA’s on all available building products, we have instead included an LCA mind-set in creating the list of line items in the Resource Efficiency section. Our hope is that in the future the prescriptive line items in the guidelines will eventually be replaced with a full LCA approach for the home as a system and the components therein.

Energy Efficiency

Energy consumption has far-reaching environmental impacts: from the mining of fossil-fuel energy sources to the environmental emissions from burning non-renewable energy sources. And each home consumes energy year after year, meaning that the environmental impacts associated with that use accrue over time. Therefore, energy efficiency is weighted heavily in a green building program.

Energy consumption occurs not only during the operation of a home but also during the construction of a home and, indirectly, in the production of the materials that go into the home. Although the energy used to heat and cool a home over its life far outweighs that to manufacture the materials and construct it, the large number of homes built (currently about 1.85 million per year) renders the energy used during the construction phase significant.  On average, a home built between 1990 and 2001 consumed about 12,800 kWh per year for space and water heating, cooling, and lights and appliances. Where natural gas is used, consumption averages 69,000 cubic feet per household annually. Total energy expenditures during a year cost these homeowners about $1,600. Energy efficiency improvements that make a home 20% more efficient—a conservative estimate for many green homes—could significantly reduce a homeowner’s annual utility expenses.  No matter what the climate, energy efficiency is considered a priority in most existing green building guidelines/programs. Moreover, as the cost to heat and cool a home becomes more unpredictable, it is advantageous to every homeowner to be “insulated” from inevitable utility bill increases. As with all aspects of these guidelines, the greatest improvements result from a “whole systems” approach. Energy performance does not end with increased R-values, the use of renewable energy, and/or more efficient HVAC equipment. Rather, there needs to be a balance between these features and careful window selection, building envelope air sealing, duct sealing, and proper placement of air and vapor barriers from foundation to attic to create a truly high-performance, energy efficient home that is less expensive to operate and more comfortable to live in than a conventionally constructed home.

Other Resources

Future green products: Geothermal, solar power

Sustainability

Green building is much more than just reducing a home’s environmental footprint. Homeowners can also realize direct benefits by owning a eco-friendly home. Here are some of the primary benefits that owners of eco-friendly homes have experienced compared with owners of conventional homes:

• Lower operating costs — Homeowners receive less expensive utility bills because of energy and water efficiency measures.
• Increased comfort — Eco-friendly homes have relatively even temperatures throughout the home, with fewer drafts and better humidity control.
• Improved environmental quality — By following these guidelines, builders pay extra attention to construction details that control moisture, choose materials that contain fewer chemicals, and design air exchange/filtration systems that can contribute to a healthier indoor environment.
• Enhanced durability and less maintenance — Eco-friendly homes incorporate building materials and construction details that strive to increase the useful life of the individual components and the whole house. Longer lasting materials not only require fewer resources for replacement but also reduce maintenance and repair costs.