By Andrew Hunt
Headlines today can put home buyers in a frenzy to contend with global warming, preserve natural resources, and help the United States become energy-independent. But according to architect and sustainable-building advocate Peter Pfeiffer, AIA, common sense, not the latest innovation, may prove a more practical approach to building economical, energy-friendly homes.
"It's about five to 10 times quicker return on the investment to do energy conservation than create a new form of energy production," said Pfeiffer during a lecture at the 2006 Energy and Environmental Building Association's (EEBA) Excellence in Building Conference and Expo. "What this means for builders is that it is much cheaper to build a home that consumes less energy than to build a home that tries to be an energy producer through solar collectors or a wind-powered system on the roof."
Pfeiffer has more than 20 years experience in the building industry and is well-versed on the practical applications of building science, including passive cooling strategies and radiant barriers. When looking at new-home design, Pfeiffer believes builders can help homeowners achieve practical energy-saving goals without spending a mint on technology. The three areas he suggests to focus on are home orientation relative to solar gain, mechanical equipment locations and roof design and color.
Position the home for comfort. "Your air-conditioning loads and your heating loads are affected by the home's orientation," said Pfeiffer. "If orientation was considered over the past 25 years in Austin, Texas, we could have reduced our energy consumption by half."
Tips to best position the home on the property to reduce solar gain include the following:
- Make sure that all blueprints have a well-placed North arrow to help architects and builders understand the home's relative position to the sun.
- Keep walls with direct afternoon sunlight as windowless as possible. While windows are an attracting selling point for the new home, Pfeiffer believes builders must design homes to be lived in, as well.
- Create buffer zones around the home to naturally insulate the living spaces. "Use large objects, like the garage as a buffer from the hot afternoon sun, or from cold winds," said Pfeiffer.
Centralize mechanical equipment. Pfeiffer suggested that the mechanical systems should be the next priority. "You know people talk about the benefits of tankless water heaters, but a good design may negate the need for multiple water heaters." Pfeiffer cites his own experience as an architect to demonstrate his point. "If we've built 600 homes, I think we've had fewer than ten that have needed more than one water heater, and we don't build small homes."
When deciding where to locate the mechanical equipment, Pfeiffer suggests the following:
- Place water heaters central to the point of first need. "Don't put the water heater out in the garage, then realize the only way to get hot water to the master bath quicker, which is on the other end of the house, is to install a re-circulating system or another water heater. Think about where you put the water heater in the first place to reduce the plumbing lines."
- Pfeiffer suggested the same approach be applied to the home's mechanical system. "Reduce the duct lines, put your air handler in a central location so that you have even air distribution and it costs less money to operate."
Provide a big sunshade for the home. "If we look at wall systems, less than 10% of our energy consumption is due to the shell," Pfeiffer explained. "The big things are the solar heat gain and infiltration of humidity." Pfeiffer contends that infiltration accounts for about half of the energy consumption in the hot, humid climate of Texas, and solar heat gain through windows or the roof draws about another third.
"In a hot and humid climate would you rather have a lot of insulation around you or would you rather stand under a shade tree? The point is to get rid of the source of discomfort, which in this case would be the hot sun beating down on us."
He suggested the following as ways to passively cool the house:
- Install white reflecting roofing materials. "Think about the color of the roof, if for no other reason than the temperature of the immediate neighborhood below it. When you think about the urban-heat-island effect, a large contributor to that is the color of the roof."
- Use a sun-angle calculator to understand how broad of an overhang is needed to protect the home from solar gain through the windows. "It would be more effective to have totally shaded single-pane windows than un-shaded double-paned low-E windows in areas of the country where you air condition a lot."
Build locally to think globally.
Builders are perfectly positioned to help their energy-conscious home buyers get beyond the headlines and find practical passive ways to conserve energy. Pfeiffer believes that one of the best ways may be to think about the local building conditions first.
"You have to do some sort of energy analysis no matter where you are building. You have to start understanding what is affecting your energy bill and the comfort of the homes in your area.
"In the Austin, Texas, area, cooling is about 40% of the energy consumption; heating is a very little percentage. Lighting is actually a larger energy user than heating, and water heating is even lower than that," said Pfeiffer. "So it is important to look at the fact that maybe we should look at energy-efficient lighting before we buy that expensive water heater, or worry too much about the efficiency of the heating system. I don't mean dump your efficient water heater or dump your efficient heating system, but prioritize the use and put the money where it will do the most good."
Andrew Hunt is a freelance writer who specializes in building technology and green building topics.
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