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Detecting Air Leaks

November 6, 2014 - 6:39pm

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For a thorough and accurate measurement of air leakage in your home, hire a qualified technician to conduct an energy assessment, particularly a blower door test.

For a thorough and accurate measurement of air leakage in your home, hire a qualified technician to conduct an energy assessment, particularly a blower door test.

You may already know where some air leakage occurs in your home, such as an under-the-door draft, but you'll need to find the less obvious gaps to properly air seal your home.

For a thorough and accurate measurement of air leakage in your home, hire a qualified technician to conduct an energy assessment, particularly a blower door test. A blower door test, which depressurizes a home, can reveal the location of many leaks. A complete energy assessment will also help determine areas in your home that need more insulation.

Without a blower door test, there are ways to find some air leaks yourself.

Visual Inspection

On the outside of your house, inspect all areas where two different building materials meet, including:

  • All exterior corners
  • Outdoor water faucets
  • Where siding and chimneys meet
  • Areas where the foundation and the bottom of exterior brick or siding meet.

Inside your home, inspect around the following areas for any cracks and gaps that could cause air leaks:

  • Electrical outlets
  • Switch plates
  • Door and window frames
  • Electrical and gas service entrances
  • Baseboards
  • Weather stripping around doors
  • Fireplace dampers
  • Attic hatches
  • Wall- or window-mounted air conditioners.
  • Cable TV and phone lines
  • Where dryer vents pass through walls
  • Vents and fans.

Also look for gaps around pipes and wires, foundation seals, and mail slots. Check to see if the caulking and weather stripping are applied properly, leaving no gaps or cracks, and are in good condition. Check the exterior caulking around doors and windows, and see whether exterior storm doors and primary doors seal tightly.

Inspect windows and doors for air leaks. See if you can rattle them, since movement means possible air leaks. If you can see daylight around a door or window frame, then the door or window leaks. You can usually seal these leaks by caulking or weatherstripping them. Check the storm windows to see if they fit and are not broken.

You may also wish to consider replacing your old windows and doors with newer, high-performance ones. If new factory-made doors or windows are too costly, you can install low-cost plastic sheets over the windows.

Building Pressurization Test

If you are having difficulty locating leaks, you may want to conduct a basic building pressurization test to increase infiltration through cracks and leaks, making them easier to detect:

  1. Turn off all combustion appliances such as gas burning furnaces and water heaters on a cool, very windy day.
  2. Shut all windows, exterior doors, and fireplace flues.
  3. Turn on all exhaust fans that blow air outside, such as your clothes dryer, bathroom fans, or stove vents, or use a large window fan to suck the air out of the rooms.
  4. Light an incense stick and pass it around the edges of common leak sites. Wherever the smoke wavers or is sucked out of or blown into the room, there's a draft. You can also use a damp hand to locate leaks; any drafts will feel cool to your hand.

If you don't want to turn off your furnace, you can just turn on all your exhaust fans to depressurize your home.

Other air-leak detection methods include the following:

  • Shining flashlight at night over all potential gaps while a partner observes the house from outside. Large cracks will show up as rays of light. Not a good way to detect small cracks.

Shut a door or window on a dollar bill. If you can pull the dollar bill out without it dragging, you're losing energy.

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