Oct./Nov. 1983 RAIN Page 45 wall plug outlets, fan fixtures, doorways, and the laundry chute. One house visited was a conservation specialist's gold mine. This was a 40-year-old, 1300-square-foot house with a half-basement and a rubble rock foundation. It had an electric forced-air heating system, a little-used fireplace with glass doors, and a remodeled bathroom. On fiirst glance, the house seemed to have a few leaks, but when the Blower Door was installed, the House Doctors discovered a very high rate of outdoor/indoor air exchange, meaning that mere were some large holes somewhere. Upon closer examination, and with the help of smoke- sticks, they located the major problem areas. Smoke was disappearing quickly around the cedar-trimmed bathtub and the French doors, and was being sucked up the chimney around the glass doors on the fireplace; daylight was visible through cracks in the foundation; and an eight-inch heating duct was not hooked up to anything, so it was warming the crawl space under the house. To remedy these problems, the House Doctors sealed holes with insulation, caulked and weather- stripped all the doors, including the French doors and fireplace doors, patched the foundation mortar, and sealed the mystery duct under the house. After these changes, the Blower Door test showed a 39 percent reduction in heat loss. Thirty-four of the 50 houses doctored had pre- and post-doctoring examinations. They showed an average heat loss reduction of 25 percent (saving 2,220 kWh/yr.) and an annual savings of over $122 (at 50 per kWh). This means that with the present cost of energy in CORR's service area, the payback period for a House Doctor visit is about three and a half years. As good physicians, CORR's House Doctors also prescribed lifestyle changes to head off future ailments. They emphasized to homeowners how simple changes in daily habits could further enhance energy savings. CO^'s program was very effective for the 50 households that participated; however, the CORR staff did not reach one of their goals. They had hoped to train homeowners and renters to seal leaks themselves, but despite announcements, phone calls, and mailings, only one organization expressed an interest in cosponsoring the House Doctor workshops. This lack of public interest was discouraging to CORR personnel; in retrospect, it seems likely to them that scheduling the program in the fall, rather than the spring, and a more ambitious advertising campaign might have produced more positive results. The biggest obstacle to the spread of House Doctoring programs throughout the country is a fear about possible reduction of air quality in homes. When all the holes in a house are plugged, harmful indoor air pollutants have no means of escape and fresh air has no way to enter. However, the Blower Door makes it possible to ensure that no house is tightened beyond a safe air quality standard. Also, an air-to-air heat exchanger (see discussion of Alan Boner's heat exchanger project below) provides a solution to the problem by circulating and exchanging indoor and outdoor air. When researchers at the Bonneville Power Administration complete their studies of indoor air pollutants and set safety guidelines for "tightening" a house, the House Doctor program and the Blower Door may become part of standard conservation education programs in the Pacific Northwest. In fact, the Blower Door may become a household word soon. (Mike McKeever, Conservation Management Services, 1012 NW Wall, Suite 203, Bend, OR 97701.) Low-Cost Residential Heat Exchanger Heating your home has become ever more expensive in recent years. Many people have responded to this "utility bill crisis" by insulating and weatherizing their houses. But increased energy efficiency has led to a whole new range of problems, especially in modern, air-tight buildings. For example, indoor air pollutants can increase to harmful levels when airflow into and out of a house is reduced severely. Also, accumulated moisture from showers and cooking can contribute to accelerated wood decay, a homeowner's nightmare. Air-to-air heat exchangers deal with the problem of ventilation by increasing the indoor/outdoor air exchange. At the same time, they draw excess moisture from indoor air and channel it down a drain. More important, indoor heat is transferred to incoming air, resulting in decreased energy bills. Alan Boner of Eugene developed a low-cost, easily-installed heat exchanger that attaches to a clothes dryer and recovers heat from the dryer exhaust. Picture a heat exchanger as a long, thin box with a thin membrane dividing it in half lengthwise, forming two parallel flow paths (see diagram). The membrane acts as a thermal conductor between the two oppositeflowing air paths. So, hot, stale air entering at one end releases its heat via the membrane to the colder, fresh air entering through the opposite end. Fans assure a smooth airflow. In short, a heat exchanger conHnuously warms fresh incoming air using the warm, stale, exiting air, thus reducing home heating costs. Alan Boner's design is a 7-foot long, 3-inch by 12-inch box containing several narrow airflow passages, with a supplementary fan attached. The box is placed flat against the wall behind the clothes dryer. In 1981, Boner received a U.S. Department of Energy grant to purchase measuring and testing equipment for his prototype. He monitored intake, exhaust, airflow, and pressure level variations between the two sides of the exchanger, and then modified the design to increase its efficiency. For example, the first design looked like a
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