A SECOND-generation, energy-efficient residence conceived during the energy crisis because of the need to evaluate innovative conservation materials and building techniques is being built near Baltimore.
The National Association of Home Builders Research Foundation, under contract with the U.S. Department of Housing and Urban Development, is building the house, Energy Efficient Residence 2 (EER-2), in an effort to evaluate the effectiveness of innovative energy conserving concepts.
Among the techniques that will be tested in the house are passive, or non-mechanical, space and water heating, a rock bin for storing surplus shaft and an earth source heat pump which obtains heat or cold from the ground.
EER-1, the precursor to EER-2, was built in 1977 in Mount Airy, Md., north of Washington. The house was designed to evaluate the effectiveness of readily-available and conventional "off-the-shelf" methods of improving energy efficiency in houses. A virtually identical Conventional Comparison House (CCH) was built next to it using standard construction methods and regular amounts of thermal protection. Then the houses were rented to two families (each with two children and two adults) for a year in an effort to compare energy usage patterns in the two houses.
The results of the EER-1 and CCH comparison show energy consumption can be reduced substantially through the use of currently available products and techniques. The bottom line -- though some materials and techniques were clearly not cost effective -- is that EER-1 used 49 percent less energy than the CCH.
The EER-2 house is designed to evaluate materials and techniques that are not commonly available today but may be in use 5 to 10 years from now.
Whereas EER-1 was a rather conventional ranch house with a full basement, EER-2 uses design elements commonly described as "California contemporary."
The research foundation, said Donald F. Luebs, project director, deliberately made the new house somewhat more of a "show house." In addition, the designers were not as concerned with cost as with the EER-1, Luebs said, because the house probes the future and many of its features are innovative.
There will be no comparison house because the researchers know enough about construction of existing houses at this point to make accurate comparisons, Luebs said.
In the fall, after some preliminary studies, the house will be rented and monitored for a year to test the efficiency of its special features.
The EER-2's floor plan shows on the upper level a two-car garage with a door that opens into a vestibule air lock -- rather than the house itself. A central foyer leads into the 21-by-13 living room is a glass-enclosed solarium with deck. Also on the lower level are bedrooms on both sides of the family room, a storage room, a full bath, a mechanical room and a heat-storing rock bin.
The house is situated so that the two-story rear wall with large windows faces south for maximum passive solar gain. All rooms except the kitchen, which has internal heat gain from appliances, are located on the south side of the house. The two-level solarium (lower level) and deck (upper level) act as passive solar collectors. Sliding glass doors separate both from the main part of the house when necessary.
Noticeably missing from the large house is a fireplace. The research foundation designers deliberately designed the house without a fireplace or provision for wood-burning stove.
The reason, said Luebs, is simple. Research shows that the ideal fireplace would be free-standing rather than built through an outside wall, draw combustion air from outside, circulate room air around the firebox and back into the room, have a tight-fitting damper and be fitted with glass doors. The EER-1 fireplace had all of those features but contributed nothing to energy savings. The conventional fireplace in the comparison house was a major source of energy waste.
The key element in the EER-2 and in any energy-efficient house, Luebs said, is insulation. The EER-2 has a pressure-treated wood foundation with R-30 insulation.
Although wood foundations are not common in this area, it allows foundation-level insulation difficult to achieve with a concrete block foundation. There is also plaxtic foam insulation under the concrete slab, around the exposed slab edge and over band joists.
Heavy insulation is also used in the exterior walls and over winder and door openings. Doors are insulated steel with weatherstripping and windows are double glazed. Thermal shutters with an R-14 rating are stored in wall pockets during the day and can be pulled out at night to prevent heat from escaping through windows which have very low R-ratings. The ceilings have an R-33 rating.
The two-story solarium with deck on the upper level serves as a passive solar collector to channel heat into the living area of the house. But the solarium ceiling also has a vent shaft to allow heat to escape in the summer. Overhangs shade the south-facing windows and solarium in the summer to prevent solar gain.
The solarium also channels heat into a rock bin storage area which Luebs said is designed to store enough energy to heat the house overnight. A heat pump extracts heat or cold from the earth and a heat recovery system extracts heat from household water to supplement space heating. A whole-house fan cools when air conditioning is not necessary.
Kitchen appliances are high efficiency and the heavily insulated electric waterheater is set at 120 degrees. EER-1 showed that reducing hot water heater temperature is one of the most cost-effective steps a homeowner can take to save energy.