Detecting Window Leaks

August 6, 2014

A little time spent now detecting window leaks in your home will pay big dividends down the road. The savings from this preventative window inspection can be as simple as reduction in your monthly utility bill or huge savings by avoiding costly repair bills. Here are several simple methods you can use to detect window leaks including the home pressurization test, the flashlight test, the paper gauge test, and a simple visual inspection for damage caused by window leaks.

Home Pressurization Box Fan Test

To locate small, yet potentially costly window leaks, you may need to perform a home pressure test:

  • To begin the test, be sure to close all vents and dampers, close all windows, doors, and skylights, and turn off all fans including kitchen fans, ceiling fans and bathroom exhaust fans.
  • To create a negative pressure in the home, mount a large box fan in one window opening.
  • Light an incense stick and slowly follow the path around the edge of your windows. If the smoke waivers you have likely discovered a small leak.

The results of the home pressurization test can be more effective if performed on a windy day.

Flashlight Window Leak TestThe Flashlight Test

To locate large leaks around windows and doors you can perform the flashlight test. This test must be conducted with two people in a coordinated effort, and must be accomplished at night.

    • Using a flashlight, the person inside the home will direct the flashlight at the window frame or door frame and follow a path that encompasses the entire perimeter of the window or door.
    • The person outside will keep a watchful eye for a beam of light shining around the exterior frame.
    • This test will only detect large window leaks and will only be successful if the two parties are in sync.

The Paper Gauge Window Leak Test

This test will detect a potential leak at the bottom of double hung windows when they are closed.

      • Open each window one by one
      • Place a sheet of paper on the window sill and close the window
      • Pull out the sheet of paper

If you can remove the sheet of paper without it tearing the gap is large enough to cause an air leak.

Visual inspection for damage caused by window leaks

      • In the interior of the home, inspect all window frames and the drywall surrounding each window for water stains
      • Using the tip of your finger or knuckles, aggressively tap the wood siding around the window, the window sill, and the window frame itself. If you discover any soft areas the damage was likely caused by a leak and must be repaired before further damage occurs.

Still worried about home window leaks? Simply don’t have the time to inspect your home for window leaks yourself? Then contact One Source Renovation at Give us a call at (815)-634-8922.