Building Quality Homes in Cold Climates
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Homes that withstand below-freezing temperatures and snow for several months, the possibility of rain and thunderstorms for almost the whole year, and high temperatures and humidity in the summer months have to be pretty darn tough—but can they be energy efficient?
The cold climate zone is the largest in area in the United States, stretching across the northern portion of the entire country. The wide range of temperature, humidity, and precipitation extremes in this climate zone mean that homeowners can use a lot of energy and pay a lot of money in utility costs to remain comfortable, particularly if their home is inefficient. The good news? A home can operate very efficiently and offer excellent comfort in a cold climate, keeping your customers warm and cozy, and their utility bills low.
IBACOS, along with the U.S. Department of Energy’s Building America Program, has developed strategies to help production builders build quality homes that achieve 40% energy savings in residential space conditioning, hot water, and lighting loads. These strategies require following a design that carefully considers how each component of the home interacts with others to ensure overall quality. These strategies are based on our work with a number of single-family homebuilders in the cold climate zone to identify solutions to those construction practices that present the greatest challenges to improving energy efficiency and overall quality. Here’s what we found:
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IBACOS Recommendations |
The exposed thermal enclosure, such as exterior walls, windows, or attic space, could be bundled up against the elements better, so that less energy is needed to keep the home’s interior comfortable.
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Windows are the weakest link in letting in winter’s frosty breath and summer’s fiery rays. Use double-glazed low-emissivity windows with argon fill to reduce heat loss in winter and limit heat gain in summer. The square footage of all windows should amount to less than 21% of total floor area, with no more than 15% preferred. Exterior walls should have at least R-16 thermal performance and attics should have a minimum of R-38 insulation.
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Foundation construction practices could be improved to increase energy efficiency and reduce moisture problems.
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Homes in the cold climate zone that are otherwise energy efficient can lose as much as 50% of their heat through an uninsulated foundation. And because basements are often used as living space, insulating the foundation is critical for maintaining comfortable temperatures, particularly in the winter. Insulate the full height of basements on the exterior side of the foundation wall to R-10 minimum, including the band joist area. If basements and band joists need to be insulated on the interior, use an interior air and vapor retarder, and make sure local building code flame spread requirements are met. Crawl spaces should be insulated the same as basements, be unvented, and receive conditioned air.
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Building airtightness should be improved to minimize heat escaping from the home due to gaps in the building enclosure. This is especially important from a customer satisfaction standpoint, as builders often experience complaints about areas being uncomfortable due to drafts or cold spots.
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Airtightness means no drafts, and more comfortable customers. Make the air barrier continuous for all walls, ceilings, and floors. Install insulating foam sheathing as the exterior part of the air barrier for walls. Install draftstopping where there are gaps in the interior air barrier. Don’t leave insulation exposed to unconditioned spaces. Best practice details for proper insulation of knee walls can be found in the July 2003 issue of the Quality Home® Newsletter.
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The typical space conditioning and domestic hot water production systems had minimum levels of energy efficiency, could pose indoor air quality hazards, and are sometimes located in unconditioned space and, therefore, are subject to extreme temperature conditions.
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Use a 90% annual fuel utilization efficiency (AFUE) sealed combustion furnace and an air-conditioning unit with a properly paired condensing unit and evaporator coil to achieve a seasonal energy efficiency ratio (SEER) 12 rating. Size the HVAC system based on actual thermal characteristics, and calculate heating and cooling loads according to ACCA Manual J. Locate all equipment within conditioned space. For more information, see HVAC Optimization Strategies in the March 2003 issue of the Quality Home® Newsletter. IBACOS recommends power-vented gas-fired hot water tanks with an energy factor (EF) greater than 0.56, and electric units with a minimum 0.88 EF.
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Air distribution systems are often inefficient at delivering conditioned air and maintaining a balanced pressure situation in bedrooms, and can draw return air from unwanted locations.
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Design the air distribution system using area Manual D methodologies, and provide a carefully detailed layout to field personnel. The air distribution system must be fully ducted, run in conditioned space, and should have all joints and openings sealed with a UL-181 approved water-based mastic sealant. A central return with jump ducts or a return grille strategy provides a balanced pressure situation in all bedrooms. A mechanical ventilation system, either a continuous exhaust system or a balanced system such as a heat recovery ventilator, should be used to enhance indoor air quality. For more information, see the article on mechanical ventilation in the May 2002 issue of the Quality Home® Newsletter.
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Lighting is often selected mainly on aesthetic value and cost, with little or no consideration given to its impact on comfort and energy use.
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Use compact fluorescent lights (CFLs) with a color temperature of 3000K and a color rendering index above 80 to lower electric consumption and limit heat output. CFLs are available for almost all fixtures, have a very long life, are very energy efficient, operate like other lamps, and can be found at a reasonable cost.
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This article summarizes a technical paper written by IBACOS’ John Broniek. For a copy, or to learn more about our work, contact Stacy Hunt at shunt@ibacos.com.
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