Installing ductwork outside your home is difficult enough, but indoor installation is worse. Putting ductwork in your home is a delicate but necessary task. Ductwork in the attic requires careful installation—attics hold in the summer heat and cool to the winter temperatures. With such extremes, ductwork does not survive very well in attics. Many areas of your home appear to be good installation sites, but in reality ducts require specific conditions in order to function properly.
Architects and builders often do not leave enough space in your home for furnaces, air conditioners, and ductwork. This forces homeowners to fit the ductwork wherever there is room. Ducts installed in vented, unconditioned attics are exposed to extreme temperatures and humidity. In the summer, attics heat up to 120-130 degrees Fahrenheit. The underside of a roof with asphalt shingles reaches 170-180 degrees in the summer. This extreme heat transfers radiant energy to the duct’s surface to raise its temperature well beyond the attic air temperature. This difference in duct and air temperatures disrupts the duct’s functioning.
Attic and ceiling insulation provide a radiant barrier that is necessary for ductwork to function properly. When you install leaky ductwork in an un-insulated, unconditioned attic, the problems increase. Without insulation and air sealing, your ductwork sucks all of your conditioned air into your unconditioned attic. Essentially, leaky ducts make your home work three to fives times harder to control the indoor temperature.
The ideal home has an airtight ceiling, a vented attic, proper attic insulation, and all of the ductwork within the conditioned space. When the ductwork is installed in the attic, your home loses about 10% more energy compared to the ideal home. This is not as bad as a home without insulation and air sealing, but is still not the best option to help you save. If your ductwork is in an unconditioned space and your home is not effectively sealed, you will lose more than 30% more energy than the ideal home design.
Regardless of duct location and home insulation, making the ducts airtight will protect your home from unwanted energy loss. In our New England climate, our homes need as much protection from air leakage and the outside weather as possible. By insulating around your ducts, you can cut that 10% energy loss down to only 5% away from the perfect home.
Now you know the importance of sealed ductwork. You have many options to improve your ductwork, and thus improve your home’s energy efficiency. A home’s ductwork can only achieve maximum efficiency if the home is insulated and sealed. After you tighten your home, it is time to consider different approaches to modifying your ducts to be more energy efficient.