For some decades now our government has been exhorting us to build houses that consume less energy. The rationale has changed over time from reducing dependence on foreign oil imports, to lowering utility bills, to reducing summer peak-load electricity demands that cause brown outs. We now have another, much more serious reason to build houses that use less energy – global warming and green house gases.
Most homeowners are aware of this phenomenon, but most assume that the emissions causing the problem come from the millions of vehicles on our highways and the belching industrial smokestacks located in nearly every state. But here in the U.S., the largest source of carbon dioxide emissions, which account for 85 percent of all green house gases, are buildings. And half of these are houses.
An easy way to grasp the scale of this problem is to think in terms of cars. Every year, the amount of emissions attributable to each house in America is equivalent to that of two cars, each driven 10,000 miles a year. With about 80 million houses out there, this is 160 million cars worth of pollution, said Ren Anderson of the National Renewable Energy Lab in Golden, Colo.
These astounding facts are easily explained. We depend on fossil fuels to live in our houses and when these are consumed they produce carbon dioxide and small amounts of other green house gases such as methane. For heating, our furnaces run on natural gas or oil and vent the smoke up the chimney. For cooling and everything else in our houses that require energy to operate, we depend on electricity. The majority of our electricity is generated at coal-burning power plants, and these are hugely polluting.
Addressing the residential emissions issue head-on, the Department of Energy’s Building America program has set the goal of reducing energy needs in new houses by 50 percent within the next 10 years. This will reduce their carbon emissions by 50 percent.
The standard against which new houses will be measured is the average energy use for a new house in 2003.
Anderson, who manages research for the Building America program, said this ambitious goal can be achieved with some modification to conventional home building practices and the adoption of some newer building products that are widely available. But he also acknowledged that success requires that Building America not just encourage home builders to participate in its program. It must also engage the buyers of these new houses because the house itself only accounts for 42 percent of the total amount of energy used. The rest goes to operate all the appliances, computers, entertainment equipment, gadgets and doodads that most households own.
The buyers’ first purchase for their new house should be Energy Star appliances, which many builders now offer in their base-priced house. On average, major appliances consume about 16 percent of a household’s energy consumption; Energy Star models reduce this by about 3.4 percent. Buyers can make additional energy cuts by purchasing Energy Star models for other items such as televisions and computers. Since its inception in the early 1990s, the Energy Star program has grown to more than 40 product categories.
Lighting is another energy drain that buyers must tackle. It currently consumes about 12 percent of the average household’s total energy use. This can be cut by two-thirds simply by switching out incandescent bulbs for Energy Star compact fluorescent lamps (usually called CFLs) that screw into a standard incandescent bulb socket. Though more expensive, Energy Star CFLs last up to 10 times longer than standard incandescent bulbs and the latest generation has been color corrected to produce the same quality of light.
To increase the energy efficiency of the house itself, Anderson’s group has worked with builders, manufacturers and building scientists around the country to develop different strategies for different climate regions. New products and building practices are “road tested” in pilot projects and deemed to be cost-effective before they are recommended to home builders. Some changes require only minimal modification to conventional building practices; in other cases the learning curve is steeper, but “definitely not insurmountable,” Anderson said.
Anderson’s suggested changes to the house are not costless, however. On average, he said, they add about $10,000 to the cost of 2,500-square-foot, two-story, four-bedroom houses that are standard offerings in most housing markets.
Many of Anderson’s recommendations simply ratchet up the efficiency of standard house parts. The windows should not only be dual-paned, they should also have a low e coating, which many, but not all builders now offer as standard (a low e coating keeps the heat inside in winter and outside in summer). The walls should be framed with 2-by-6 studs, so that more insulation can be added. To prevent the escape of conditioned, heated or cooled air to the great outdoors, air leaks should be conscientiously plugged up. A gas furnace should be a 90 percent or higher fuel-efficiency model because it converts gas to heat more efficiently and thus uses less (this also means a lower gas bill). All home builders are now required to provide a 13 SEER air conditioning compressor; Anderson recommends an even more efficient 15 SEER model.
All the ducts should be sealed with mastic, a gray, gloppy glue-like substance instead of tape, which eventually disintegrates and allows as much as 25 percent of heating and cooling energy to be lost. Anderson also recommends putting all the ducts in the living area instead of in the attic, a standard practice in many parts of the country. Though attic ducts can be insulated, significant heating and cooling losses will still occur because the insulation only lowers the loss of energy, it doesn’t eliminate it. When the ducts are included in the “conditioned space,” (for example, inconspicuously run along the ceiling), their energy losses will pass into your living area, not the great outdoors. Additional energy can be saved by locating a furnace in the center of the house to shorten duct runs.
Anderson’s other target that is built into the house is hot water. This necessity of modern life consumes 12 percent of the total energy use because it is stored in a large tank that is continuously heated. Anderson would halve this with a dual strategy: A solar hot water heater that supplies about 30-40 percent of a household’s needs and a tankless hot water heater that heats water as needed for the balance.
Pulling back for the big picture perspective, Anderson said that Building America’s goals are a moving target. As new products and building practices are tested and found to enhance energy efficiency beyond the current 50 percent level, the program will raise the bar and push for higher energy savings. In a separate interview, Deputy Secretary of the Department of Energy David Garmon emphasized that reduced greenhouse gas emissions is not the only benefit of the program. New home buyers will also enjoy significantly lower utility bills and greatly increased comfort.
How soon will a Building America house be available in your market? Many building firms, both large and small, have participated in Building America’s programs since the Department of Energy started it 10 years ago. To date, about 30,000 houses have been built. More builders will participate when they sense that buyers are really serious about energy efficiency. When they pass up granite countertops that will impress their friends and relatives today for energy efficiencies that will make a better planet for their children and grandchildren tomorrow, home builders will join the Building America program in droves.
Questions, queries or a house-building story you’d like to share? Katherine Salant can be contacted at www.katherinesalant.com.
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