Zero Energy Program, With Its Many Pluses, Makes for More-Efficient Home Construction [W.Post]
source: Katherine Salant Washington Post 2004.4.10

"Houses are polluters and big houses pollute more," said David Garman, assistant secretary of energy.

Elaborating, Garman said in a recent interview that houses are more accurately characterized as "indirect polluters." That is, they consume 36 percent of the nation's electricity, and 69 percent of that electricity is produced by fossil-fueled generating plants that collectively cause more air pollution than automobiles.

Garman is now leading the Energy Department's charge to build houses that use less electricity and therefore reduce, indirectly of course, air pollution and greenhouse gas emissions.

Astropower (GE) Integrated roof PV tiles at Clarum in East Palo Alto. A standard feature for Clarum homes.

In the past, the department has encouraged building houses that use less energy for heating, cooling and hot water, which account for about 60 percent of the total energy used in the average house and can be powered by a mixture of gas, oil and electricity.

Now the Energy Department has set its sights on the other 40 percent, which is almost entirely that indirectly polluting electricity. Lighting accounts for about 6 percent of the total; major appliances, 17 percent; and smaller appliances, such as computers, televisions and cell phone battery chargers, another 17 percent.

The department not only wants new houses to use less electricity and less energy overall, but also wants these same houses to have the capacity to generate clean electricity for their own use and to send any excess to the grid for use by other households.

When enough houses within a utility's service territory can do this, the utility can meet its summer peak load without having to build additional peak-load plants, which are far more polluting. During summer peak loads, 60 to 70 percent of all electricity produced in the country is used to air-condition homes and commercial buildings.

"Clean electricity" can be generated with wind or water, but the house must be near a fast-moving stream or in a place with constant wind. Photovoltaic cells on a roof that convert sunlight into electricity, however, can be used almost anywhere, and the government regards them as a more practical solution.

To get home builders interested, the Energy Department set up its Zero Energy Homes program. A true zero-energy house is self-sufficient, generating all the energy its occupants need. This can be done, but it's far too narrow a market to capture the interest of any large-scale production builder. Instead, the department's scaled-down definition of a zero-energy house is one with 50 percent lower utility bills, compared with a new house of similar size built to a conventional standard in the same market. Cutting the utility bill by half, on average, also cuts the energy consumption by half, said Rob Hammon, a Stockton, Calif., engineering consultant [Consol]who has worked with a number of builders in the Energy Department's program.

Halving total energy consumption is still a daunting challenge.

The simplest way is by not using power: Pull the plug on half the stuff in your house, take cold showers, set the thermostat to the far side of comfort and air-dry your clothes. A more realistic and saleable approach is to cut energy from each "energy sector" in the typical house.

Using this approach to get the energy consumption down to the Zero Energy Homes program's level, however, requires a joint effort from both the buyer and the builder The builder can deliver the goods on heating, cooling, hot water and, where applicable, Energy Star appliances. (Some builders include appliances in a new-home purchase and some do not.) The buyers will have to pick up the ball with the major appliances that the builder doesn't include, and use energy-efficient lighting. To increase energy efficiency even more, the buyers can also buy more-efficient small appliances.

A custom builder who works with larger lots can orient the house to the south so that the winter sun can help heat the interior living spaces.

Production builders working with ever-shrinking suburban lots, however, rarely have this opportunity. Instead, their efforts have centered on the house itself and focused on cutting heat gain (heat coming into the house), heat loss (heat going out of the house) and air infiltration (air coming in from outside that must be heated or cooled).

Air leakage and unpleasant drafts in cold weather can be cut by making the building envelope tighter and plugging the air leaks that commonly occur around plumbing pipes and electrical outlet and switch boxes where standard batt-type insulation does not fit tightly.

To cut the heat gain or loss through the exterior walls, builders in both hot and cold climates will have to ramp up the insulation, often by as much as 50 percent.

In areas where the summer sun really beats down, a builder must also deal with radiant heat, which generally pours in through the roof and windows. He can reduce it with light-colored exterior walls and roofing material, radiant barriers (roof sheathing with aluminum sheeting laminated to its underside), and windows with low-emissivity glass and a low solar heat gain coefficient. The windows may sound exotic, but most window manufacturers make them. A side benefit: Your furniture won't fade as much.

The last bit for heating and cooling is the mechanical equipment. With all these modifications to the building envelope, the builder of a zero-energy house will have to cut the heat gain and heat loss to such an extent that a smaller-sized furnace and air conditioner will suffice. They will use less energy than the standard size for your house, but the builder can wring out even more savings with a high-efficiency furnace and air conditioner.

Another area where the builder can boost energy savings is with the water heater. These can be energy hogs, whether or not you indulge in long, hot showers, because much of the energy consumption by the water heater occurs when it is on standby. By contrast, a tankless hot water heater works on a demand basis, heating water only as it is needed. A zero-energy builder may also offer a solar water heater, but you will still need a tankless heater as backup for those cloudy days.

The builder will also install photovoltaic cells on the roof. In the Energy Department's program, photovoltaic cells may produce 60 percent to as much as 100 percent of the household's electricity needs.

About this time, you may be asking how much you will have to shell out before you can enjoy such energy efficiency?

The most expensive item will be the photovoltaic cells, but their actual cost depends on where you are buying and using them; some states and local utilities will subsidize as much as 50 percent of the purchase and installation costs.

Without the subsidy, the cost averages about $8 to $10 a watt. A two-kilowatt system that a zero-energy home builder might install on a 2,400-square-foot house would run about $16,000 to $20,000. But in California where local utilities may offer a 50 percent subsidy and homeowners get a 7.5 percent state tax credit, the cost is about $7,400 to $9,250.

Homeowners whose local utilities offer time-of-use rates will also save money. They can sell their surplus electricity to the grid during the peak daylight hours and buy it back during the off-peak night hours. Because of the difference in day and night rates, some California homeowners, for example, may save close to 100 percent of their electric bill over the course of a year, even though the photovoltaic cells on the roof may supply only about 60 percent of their electricity needs.

The cost of the building upgrades will vary, depending on where you are building. California, where the cost of electricity is high and a generous rebate for photovoltaic cells is widely available, has the largest number of home builders participating in the Energy Department's Zero Energy Homes program.

Centex Homes, Morrison Homes and Clarum Homes -- all current participants -- said that the cost of the upgrades and the photovoltaic cells for a 2,400-square-foot, single-family house averaged about $18,000 to $20,000. With Centex and Morrison Homes, the features are optional. Clarum includes them in its standard house.

How have buyers responded to the Zero Energy Homes program? Clarum's president, John Suppes, observed that the program did not top the list for his buyers at the time of purchase, but the features have clearly been a big hit.

"A year after they moved in," he said, "all they want to talk about is their zero-energy house."