(This is the fourth of an eight-part series.)
Last week I explained the importance of sealing your home from unwanted air infiltration. I pointed out some areas of great concern such as attics, crawl spaces and attached garages. The best practice for air sealing is to first have a professional energy audit performed with a blower door test and infrared camera scan. This is the best method to not only find air leaks but inadequate insulation as well. In attics, it is sometimes necessary to remove the existing insulation and spray foam the areas that air can leak through before putting the insulation back in place or replacing it entirely.
The worst air leaks come right from your homes heating and cooling ductwork. Have you ever wondered why your basement is colder in the summer than the rest of your home? It’s mostly due to duct leakage.
When the duct system is in the attic, crawl space, or outside of the conditioned space, it’s even worse. The duct system is attached to your furnace, which in turn has a fan. The fan gets air from the return side of the duct system, (cold air returns) and pushes it through the supply side of the duct system out into each rooms registers. If the supply side of a duct system in a nonconditioned space leaks air, you are adding heated or cooled air to an area that you don’t want to condition. What’s worse is that you’re causing the house to go into a negative pressure. Remember, we get the air from the cold air returns, and it’s supposed to go back into the same space after it is heated or cooled. If we take air from one area and put it into another, the first area will go into negative pressure and get air from anywhere that it can. The same is true of return air leakage, except that some of the air may get filtered first before getting back into the home.
Leaky duct systems are the leading cause of dust and allergens in the home, as well as high energy bills. To find out how bad your duct leaks are, you’ll need to have a performance contractor provide a duct performance or leakage test. Duct sealing is fairly easy to do with water-based mastic sealer or foil-backed tape. Never use duct tape, which is good for many things — just not ductwork.
For additional money-saving tips and advice, please visit http://tinyurl.com/rcgate.
Joel Wensley is a licensed mechanical contractor in Michigan, a member of the Comfort Institute and is also the president of Mechanical Heating & Cooling in Dearborn Heights.