Smaller Homes, Smaller Footprint, DEQ-commissioned Report Shows
Oregon Department of Environmental Quality
A recently completed report commissioned by the Oregon Department of Environmental Quality in collaboration with the Oregon Home Builders Association and Earth Advantage Institute concludes that constructing smaller homes is among the best ways to reduce greenhouse gas emissions and waste generation from the residential construction sector.
The report, A Life Cycle Approach to Prioritizing Methods of Preventing Waste from the Residential Construction Sector in the State of Oregon, is available on DEQ’s website at http://www.deq.state.or.us/lq/sw/wasteprevention/greenbuilding.htm.
The report concludes that of 30 different material reduction and reuse practices evaluated, reducing home size was the most beneficial. DEQ examined environmental benefits from each of these practices against a “standard” Oregon home, defined for the study’s purposes as a 2,262 square-foot, newly constructed home built to 2008 state energy codes. The study considered a “small” home to be about 1,630 square feet and an “extra-small” home to be 1,150 square feet. Many environmental benefits from small homes come in the form of reduced electricity and fuel use in the home but also include the benefits of avoided materials production, according to the report.
Residential home construction, maintenance and demolition make up about 10 to 15 percent by weight of total waste generated in Oregon each year.
“Results from this report are significant because they quantify the benefits of a variety of common green building practices, including reduced house size, on a consistent scale. That gives us a guide for the relative importance of each practice,” said Jordan Palmeri, the DEQ waste prevention specialist who oversaw the report’s commission and helped evaluate the report’s findings. “This will help DEQ and the residential building sector target waste prevention practices that maximize overall environmental benefit.”
The report examines environmental impacts of extracting, producing and transporting building materials; impacts of constructing and maintaining the home; impacts of using electricity and heating fuels during a home’s 70-year occupancy; and impacts/benefits of recycling, landfilling, or burning for energy recovery the building materials at the end of the home’s life. Environmental impacts address climate change, energy use, human toxicity, ecological toxicity, acidification and respiratory effects.
Key findings in the report:
· Of 30 different material reduction and reuse practices evaluated, reducing home size and multi-family living achieved the largest greenhouse gas reductions along with significant reductions in other impact categories.
· Reducing home size by 50 percent results in a projected 36 percent reduction in lifecycle greenhouse gas emissions.
· Reducing home size is a significant leverage point for environmental impact reduction and may be a more effective measure than achieving minimum levels of “green” certification.
· Various sizes of multi-family housing show significant lifecycle reductions in greenhouse gases.
· Families who choose or require more living space than a “small” home may lessen a large home’s impact by adding green building practices and increasing the home’s energy efficiency.
· New and existing homes of any size could incorporate internal accessory dwelling units (sometimes known as “mother-in-law apartments”) within the home as an option to increase density and reduce the square foot/person ratio, provide flexible living spaces, and achieve the environmental benefits of both small and multi-family living.
· Over 80 percent of greenhouse gas emissions over a home’s 70-year life occur during occupancy and are attributed to electricity and fuel consumption. About 14 percent of greenhouse gas impacts are tied to producing the original and replacement building materials. Constructing and maintaining the home account for about 2 percent and transportation of building materials accounts for less than 1 percent. Oregon’s existing material recycling and energy recovery system reduces greenhouse gas emissions by 5 percent over the typical 70-year life of a home.
· For other types of environmental impacts, materials contribute 10 to 40 percent of total life cycle impacts.
· Only a small amount – about 6 percent – of building material-related waste generated occurs during home construction, with about 50 percent of waste generation occurring during 70 years of home repairs and maintenance. The remaining 44 percent of waste generation occurs at the time of the home’s demolition.
· Material reuse significantly reduces the amount of waste generated and material-related impacts of production.
Quantis, a lifecycle analysis firm with a U.S office in Salem, Mass., conducted research for the report. Quantis subcontracted work to the Oregon Home Builders Association and Earth Advantage Institute, a Portland-based nonprofit that works with the building industry to help adopt sustainable building practices and reduce greenhouse gas emissions.
This report is the last of two phases in DEQ’s environmental evaluation of waste prevention practices within the residential building sector. In 2009, DEQ evaluated a list of 25 practices to identify building practices most likely to prevent residential building waste. Reports from both phases are available on DEQ’s website at http://www.deq.state.or.us/lq/sw/wasteprevention/greenbuilding.htm.
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