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The Most Practical Air Sealing Techniques

Home technology expert Ross Trethewey and carpenter Nathan Gilbert share some cost-effective ways to seal and insulate existing windows without replacing them.

Host Kevin O’Connor, contractor Nathan Gilbert and tech expert Ross Trethewey share some cost-effective ways to seal and insulate existing windows without replacing them. The team discusses efficiency ratings for older single-pane windows compared to today’s options and offers tips to seal your drafty windows from the inside.

They explain different insulating techniques, including using shrink wrap, weather stripping, and caulk. Anything you can do to decrease airflow and leakage will drastically increase comfort and energy savings.

Try Sealing Air Leaks Before Upgrading Windows

Windows usually have an R-value of 1 to 2—walls generally have an R-value between 13 and 20. Before incurring the expense of buying a new window, homeowners should try to seal any air leakage around the existing window’s frame.

Traditional New England homes usually have storm windows to create a bigger barrier during winter. Nathan also explains a newer style: screw-in aluminum with removable glass for spring and summer.

How to Check for Window Air Leaks

  • Look and feel around your windows. You can walk around your house and see any obvious cracks or holes where the building materials from your siding and window meet.
  • Turn off your lights. See If there is any daylight coming through the sides or bottom of your window. Also, on a cold day, you can hold your hands an inch away from the window to feel for any drafts.
  • You can rent a thermal camera from your local hardware store to help you detect energy leaks in your windows, ductwork, and roof, as well as missing insulation all around your house.

How to Seal Window Air Leaks

  1. Clean all areas to be caulked with soap and water, removing paint or old caulk with a putty knife. Wait for the area to dry so you do not seal in the moisture.
  2. Apply caulk to the areas sealed at a 45-degree angle in a continuous stream. Make sure the caulk sticks to both sides of the seam. If caulk leaks out of the crack, push it back in with the putty knife. If the caulk shrinks, reapply in a smooth line that seals the crack completely.

How to Seal Leaks Between the Lower Window Rail and the Windowsill

  1. Clean the area where you will apply weatherstripping with soap and water. Let it dry.
  2. Measure the window width and cut the weather-stripping to size.
  3. Apply the weather-stripping to both surfaces and ensure that the material compresses to form a seal when the window is shut.


When talking about shrink wrapping windows, Nathan refers to the Frost King Premium Cylinder, Heavy Duty, EZ Roll Shrink Window Kit.

When talking about feeling a draft in your window and removing window casing, Nathan suggests using a low expanding foam like GREAT STUFF™ Window & Door Insulating Foam Sealant.

You can find all other tools, including a caulking gun, fiberglass insulation, weatherstripping, and caulking cord at local home centers.