EnergyWise House: Elements of an Energy-Efficient House

Heat and loss: Gaps between pipes, electrical outlets, ceiling fixtures, and other similar parts of a house provide a place for conditioned air to escape, making heating and cooling equipment work harder to replace it. Credit: BobVila.com Controlled Ventilation Since an energy-efficient home is tightly sealed, it's also important and fairly simple to deliberately ventilate the building in a controlled way. Controlled, mechanical ventilation of the building reduces air moisture infiltration and thus the health risks from indoor air pollutants, promotes a more comfortable atmosphere, and reduces the likelihood of structural damage from excessive moisture accumulation. A carefully engineered ventilation system is important for other reasons too. Since devices such as furnaces, water heaters, clothes dryers, and bathroom and kitchen exhaust fans exhaust air from the house, it's easier to depressurize a tight house if all else is ignored. Natural draft appliances, such as water heaters, woodstoves, and furnaces may be "back drafted" by exhaust fans and lead to a lethal build-up of toxic gases in the house. For this reason it's a good idea to only use "sealed combustion" heating appliances wherever possible and provide make-up air for all other appliances that can pull air out of the building. Heat recovery ventilators (HRV) or energy recovery ventilators (ERV) are growing in use for controlled ventilation in tight homes. These devices salvage about 80 percent of the energy from the stale exhaust air and then deliver that energy to the fresh entering air by way of a heat exchanger inside the device. They are generally attached to the central forced air system, but they may have their own duct system. Other ventilation devices such as through-the-wall and/or "trickle" vents may be used in conjunction with an exhaust fan. They are, however, more expensive to operate and possibly more uncomfortable to use since they have no energy recovery features to pre-condition the incoming air. Uncomfortable incoming air can be a serious problem if the house is in a northern climate, and they can create moisture problems in humid climates. This sort of ventilation strategy is recommended only for very mild to low humidity climates. Heating and Cooling Requirements Houses incorporating the above elements should require relatively small heating systems (typically less than 50,000 Btu/hour even for very cold climates). Some have nothing more than sunshine as the primary source of heat energy. Common choices for auxiliary heating include radiant in-floor heating from a standard gas-fired water heater, a small boiler, furnace, or electric heat pump. Also, any common appliance that gives off "waste" heat can contribute significantly to the heating requirements for such houses. Masonry, pellet, or wood stoves are also options, but they must be operated carefully to avoid "back drafting." Beginning a Project Houses incorporating the above features have many advantages. They feel more comfortable since the additional insulation keeps the interior wall temperatures more stable. The indoor humidity is better controlled, and drafts are reduced. A tightly sealed air/vapor retarder reduces the likelihood of moisture and air seeping through the walls. They are also very quiet because of the extra insulation and tight construction. There are some potential drawbacks. They may cost more and take longer to build than a conventional home, especially if your builder and the contractors are not familiar with them. Even though their structure may differ only slightly from conventional homes, your builder and the contractors may be unwilling to deviate from what they've always done before. They may need education or training if they have no experience with these systems. Because some systems have thicker walls than a "typical" home, they may require a larger foundation to provide the same floor space. Before beginning a home-building project, carefully evaluate the site and its climate to determine the optimum design and orientation. You may want to take the time to learn how to use some of the energy related software programs that are available to assist you. Prepare a design that accommodates appropriate insulation levels, moisture dynamics, and aesthetics. Decisions regarding appropriate windows, doors, and heating, cooling and ventilating appliances are central to an efficient design. Also evaluate the cost, ease of construction, the builder's limitations, and building code compliance. Some schemes are simple to construct, while others can be extremely complex and thus expensive. An increasing number of builders are participating in the federal government's Building America and Energy Star Homes programs, which promote energy-efficient houses. Many builders participate so that they can differentiate themselves from their competitors. Construction costs can vary significantly depending on the materials, construction techniques, contractor profit margin, experience, and the type of heating, cooling and ventilation system chosen. However, the biggest benefits from designing and building an energy-efficient home are its superior comfort level and lower operating costs. This relates directly to an increase in its real-estate market value. The EnergyWise House in an ongoing project that examines energy efficient building techniques, materials, and methods. For more information on the materials and companies participating in the project, see the EnergyWise House Video Resource Library.

...Continued - Page 4 of 4 ( 1 2 3 4 )
< Previous Page