The word sustainable is bandied about without a real understanding of the term. A sustainable house would have a zero sum loss of energy and resources over its lifetime. Even the greenest of houses doesn’t come close to being sustainable. Even just the manufacture and transportation of concrete to build a typical 2,500-square-foot house generates the equivalent of 36 metric tons of carbon dioxide (or the amount of carbon sequestered by 35 acres of forest in 1 year). Meaning that simply the act of building with all new material is not really “green”.
The average new single-family American residence in 1950 was 983 square feet and housed 3.8 people (259 sq ft/person). Today, it is 2505 square feet and houses 2.54 people (986 sq ft/person). These figures demonstrate how houses have become much less efficient over the years with such drastically disproportionate size-to-occupant ratios. This is the opposite of sustainability.
New green building codes are a good start, but in reality these codes “set floors, not ceilings”. They represent the minimum that should be accomplished toward sustainability, not the maximum, so builders, cities and counties should be encouraged to exceed the standards.
The California Energy Commission’s 2007 Integrated Energy Policy Report established the goal that new building standards achieve “net zero energy” levels by 2020 for residences and by 2030 for commercial buildings. A net zero energy building consumes only as much energy on an annual basis as can be generated with an on-site renewable energy system. With three short years to go, instead of moving closer to this goal, the City of Belmont is recommending significantly increasing house size – the single biggest culprit in energy consumption.
Normal size houses are almost always greener than big houses. A recent article in the Journal of Industrial Ecology concluded: A 1,500-square-foot house with mediocre energy-performance standards uses far less energy for heating and cooling than a 3,000-square-foot “green” house of comparable geometry that has much better energy detailing. Size for the sake of size creates a vicious financial and resource-wasting cycle. Buyers spend more on their homes, more to heat and cool them, and more on resources to maintain them.
Here are some examples:
The shape of a passive or a low energy house should be kept simple and should follow the rule that the area of the building envelope should be as small as possible. In other words smaller is “greener”.
A great deal of attention is paid to material selection and energy detailing in creating environmentally friendly (“green”) houses. Designers, builders, or owners of these houses seek out recycled-content building materials, low embodied- energy materials, or natural materials. Advanced framing techniques reduce wood use. Well-insulated walls and ceilings, high-performance glazing, and efficient equipment reduce energy consumption. But far too often, the more important consideration of size is overlooked. The bells and whistles of “green” materials and techniques are used to mask the unfortunate fact that the basic size of the home is not “green”.
A 1,500-square-foot (141-m2) house with mediocre energy-performance standards (R-13 walls and R-19 ceilings) will use far less energy for heating and cooling than a 3,000-squarefoot (28-m2) house of comparable geometry with much better energy detailing (R-19 walls and R-30 ceilings).
Downsizing a conventionally framed house by 25% should save significantly more wood than substituting the most wood-efficient advanced framing techniques (24”-on-center studs, single top-plates, two-stud corners, elimination of cripple studs at windows, etc.) for that house. And it is easier to reduce the embodied energy of a house by making the house smaller than by searching for low embodied- energy materials.
References:
- https://www.greenbiz.com/news/2005/07/12/small-beautiful-us-house-size-resource-use-and-environment
- http://www.alternet.org/story/61523/big_houses_are_not_green%3A_america’s_mcmansion_problem
- https://sites.google.com/site/lowenergyhome/architectur
- http://www.energy.ca.gov/title24/2016standards/background.html
U.S. Department of Energy Report quotes:
The 97.8 quads of energy the U.S. consumed in 2010 represented 19% of global consumption—the second largest share of world energy consumption by any country; only China consumed more. But on a per capita basis, the average American consumed almost 4 times more energy (1843 watts/person) than the average Chinese (474 watts/person).
- The U.S. buildings sector alone accounted for 7% of global primary energy consumption in 2010.
- In the United States, the buildings sector accounted for about 41% of primary energy consumption in 2010, 44% more than the transportation sector and 36% more than the industrial sector.
- Total building primary energy consumption in 2009 was about 48% higher than consumption in 1980.
- Space heating, space cooling, and lighting were the dominant end uses in 2010, accounting for close to half of all energy consumed in the buildings sector.
- Forty-one percent of U.S. primary energy was consumed by the buildings sector, compared to 30% by the industrial sector and 29% by the transportation sector.
- Of the 39 quads consumed in the buildings sector, homes accounted for 54% and commercial buildings accounted for 46%.
- Of the energy sources used by the U.S. buildings sector, 75% came from fossil fuels, 16% from nuclear generation, and 9% from renewables.
- U.S. buildings have come to represent an increasing portion of the country’s carbon dioxide emissions—40% in 2009, compared to 33% in 1980.
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