Finding air leaks

Common sites for air infiltration
A thorough home inspection can reveal dozens of hidden energy wasters.
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Air leak chart - courtesy Iowa Energy Center

The first step in tightening up your home is finding the air leaks that need to be sealed. Why? A 1/16th-inch unsealed crack around a window can let in as much cold air as leaving the window open three inches!

The chart at right shows the primary places outside air infiltrates your home. Most are easy to fix with some inexpensive weatherizing materials:

If you’re not sure where to start, try Alliant Energy’s My Home Comfort Check Up energy audit - this free analysis will help you pinpoint energy wasters and learn how to improve your home's efficiency. You can choose the options that fit your needs and your lifestyle.

Measuring existing insulation

Before you head to the home store or call a contractor, you’ll need to measure the amount of existing insulation. To find out, you'll need a flashlight, a ruler, a screwdriver and maybe a ladder.

  • Measuring insulationThe first stop is the attic. Measure the depth of the insulation on your attic floor.
  • To check sidewall insulation, remove the cover plate from an electrical outlet or light switch on an exterior wall [be sure to shut off power at the service panel first], and use the flashlight to check for insulation behind the metal box.
  • If you can't see behind the box, remove a baseboard in a hidden area, such as a closet - you might see insulation poking out the bottom.
  • Go to your basement and check the rim joist - the long, thick board that sits on top of the concrete foundation. You might see insulation in the pockets between each floor joist.
  • If you have a finished basement, remove an outlet cover to check for foundation insulation - here it may be thick foam sheets instead of fiberglass.

Blower door tests

If you’re not sure where to start weatherizing, a blower door test - performed by a certified energy auditor - can be a great investment in tightening up your home.

Blower door testAll windows and doors are closed, and a variable-speed fan is installed in the front door with a special air-tight seal. As the fan is turned on, the energy auditor will monitor the flow of air through the fan, as well as the air pressure inside your home.

Because your home is sealed and evenly pressurized, it’s easy to find out exactly where air leaks are occurring. While you’d probably expect to find drafts around windows and doors, you might be surprised to learn how much air can leak around electrical outlets and plumbing pipes.

Blower door tests can also help identify sources of indoor air quality problems, such as carbon monoxide.

A blower door test will cost around $200-$500, depending on the size of your home. If you follow the advice you receive for weatherizing, you could recoup the cost of the test in energy savings in as little as two years.

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