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Finding Leakage Areas


How to Locate Air Leaks
The first step is to identify where the leaks occur. Air leaks where there is a hole in the building envelope and a pressure difference. In winter, the house tends to operate like a big, fat chimney. This means that air enters at lower levels and exits at the upper levels and ceiling.

Identifying specific leakage areas can sometimes require a little detective work. You can do your own detective work by making a "leak detector" and using the checklist of leakage areas to locate those places where air is leaking.

Leak Detector
An easy way to locate air leaks is to make yourself a leak detector. All you need are incense sticks. Hold two or three together for more smoke and easier detection. Powerful leaks will cause the smoke to dissipate and the tips of the incense to glow. Slower leaks will cause the smoke to trail away or move toward the leak.

On a cold day, check for drafts in all suspected areas. It is easier to locate air leaks on windy days. You'll be surprised to discover how many spots need to be sealed with caulking or weatherstripping. You should also check for possible leaks in interior walls and in other features of your house, such as fans, lighting fixtures and electrical outlets. Any direct route through partition walls or along floor joists to the outside should be sealed.

Pressure Test
Professional air-sealing companies often use a depressurizing blower door test to identify and measure the air leaks in a house. A powerful fan is inserted in a doorway, and all intentional openings – windows, doors, chimneys and vents – are closed or sealed. The fan depressurizes the house, and leaks are easily identified where air rushes into the house. A professional blower door test can also determine the total leakage area in the house, the extent of the work required, the effectiveness of the work as indicated in a post-retrofit test, and indications of backdrafting and spillage problems.

You can perform your own rudimentary blower door test by closing all windows and doors and turning on all the exhaust appliances in the house. These include bathroom and kitchen fans, clothes dryers (on cool cycle) and any portable fans placed in windows (if you can seal around them). Be careful during the test. Turn off the furnace and water heater (if fuel-fired) to prevent backdrafting caused by other exhausting devices. You can now go around the house with your leak detector and identify and mark the air-leakage locations that should be sealed.

Checklist of Leakage Areas
A few areas of the house deserve special attention, but don't limit your detective work to just these places.

Inside the main living areas, check the following:

  • window-glass panes for tightness, and around both the window sash and the window casing
  • around the door, including the threshold and around the door frame
  • electrical outlets, including those on interior walls
  • exhaust fans and vents (these should vent to the outside and close properly when not in use)
  • corners where two walls meet with an imperfect seal
  • light fixtures in the ceiling
  • interior trim and baseboards
  • cracks in the wall finish or ceiling
  • joints where wood-frame walls join a masonry wall or chimney
  • doors and hatches into unheated attics
  • fireplace dampers and fireplace bricks
  • behind bathtubs and under sinks
  • above sliding pocket doors
  • around plumbing pipes and ductwork
  • Warning: If you find older vermiculite insulation in your home, do not disturb it and consult the free Health Canada publication "It's Your Health – Vermiculite Insulation Containing Asbestos". To obtain a copy, call 1 800 443-0395.

Inside the attic, check the following (you may have to move aside existing insulation):

  • around the plumbing stack and any other pipes entering the attic
  • around wires or ceiling light fixtures that penetrate the attic floor
  • around ducting that enters the attic from inside the house
  • the junction of the ceiling with interior wall partitions
  • attic access doors
  • around chimneys
  • along shared walls
  • the ceiling area over bathrooms and stairwells

Inside the basement, check the following:

  • wherever the wood-frame wall (sill plate) meets the masonry (concrete or stone)
  • foundation or where joists penetrate the masonry wall
  • holes or gaps where electrical lines, gas lines or oil-fill pipes go through the wall (be careful!)
  • holes for wiring and plumbing going into external walls
  • leaky ducting or poorly fitted hot-air registers or cold-air intakes
  • around window and door framing
  • cracks in the foundation wall and slab
  • floor drains