Feb 4, 2010 4:00 PM  PST

Insulation + Air Sealing Is a Winning Combination for an Energy-Efficient Home

by Gale Tedhams, Director of Sustainability
Despite major strides in energy efficiency, the number one user of energy in the U.S. continues to be buildings, which consume 40 percent of our nation’s energy resources – more energy than industry and more than transportation.  
While it’s well known today that a properly insulated building uses less energy for heating and cooling than the same un- or under insulated building, what is less known is that air infiltration is also a major factor in how much energy a building uses for heating and cooling.  
By using a system that combines both insulation and air sealing, builders can differentiate their homes with advanced energy efficiency.
Wasted Energy is Wasted Money
The U.S. Department of Energy estimates that space heating and cooling accounts for almost half of a home’s total energy use. A large source of a home’s heat loss or gain, and resulting energy waste, is from air leakage or air infiltration. In fact, according to the North American Insulation Manufacturers Association (NAIMA), air infiltration through a home can account for as much as 35 percent of the home’s energy use.
While homeowners would be crazy to heat their homes by burning dollar bills in the fireplace, it’s a perfect way to illustrate to your customer how they will waste money each year by paying for heat that escapes from their home due to inadequate insulation and lack of proper air sealing.
There are many options for insulation. Your installer can provide a performance comparison of the most common materials to obtain the right R-value for each aspect of the job. However, no matter how much insulation you use in your building project, if it isn’t working with an air barrier as an energy conservation system, your buyers will still be losing money for the life of the building.
Sealing the Deal
Since air infiltration is crucial to a building’s energy use, what can a builder do to reduce it?
To achieve exceptional energy-efficiency in buildings by reducing air infiltration, the builder must seal any gaps in the building’s thermal enclosure. Installing high-quality, tightly sealed windows and doors is a good start. It’s equally important to seal all gaps or joints between the walls and ceiling, the walls and flooring, wall-to-wall sections, wall-to-window junctions, and wall-to-door junctions. Penetrations through the walls and ceiling for electrical wiring and for plumbing also need to be sealed.
There are several options for creating a lasting air barrier. Again, talk to your installer about new foam-based sealants and caulks. While appropriately selected caulks can be effective as air infiltration barriers, they must be carefully applied prior to the insulation and inspected to assure that all potential leak locations have been fully plugged. Applying sufficient quantities of caulk to effectively seal all potential sources of air infiltration is labor intensive, difficult to do well, and can yield unpredictable results.

Whatever solution you purchase, make sure the properties of your air sealing barrier demonstrate adhesion to common building material substrates over time so the sealant doesn’t crack and become ineffectual in the future.
As today’s home buyer increasingly looks for new solutions to combat energy waste, builders will find that establishing a building system that combines air sealing with insulation will yield the one-two punch that reduces future energy bills for the life of the home.
Owens Corning is a Build It Green Contributor Sponsor.

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