Window air conditioners are made to fit most windows. With adjustable panels on the sides and flanges on the top and bottom, they fit snugly in place with little effort. However, with most models you’ll probably need to install weather seals, which are foam strips that go along the window frame, to prevent air from escaping or entering. Many window air conditioner manufacturers will include a roll of weather seal with the unity, but you also can find it at most hardware stores. Installing weather seal for a window air conditioner is a task most homeowners can complete themselves.
Open the window and clean all parts of the frame using a damp cloth. To clean away mildew or stuck-on dirt, wipe with soapy water, then rinse the window with clean water.
Dry the window frame with a paper towel. Make sure the surface is fully dry before you try to install the weather seal.
Measure the width of the bottom side of the open window. Cut a piece of weather seal to this length using scissors.
Peel the paper backing off the cut strip of weather seal, then position the seal sticky side up along the underside of the window frame. Press the seal against the frame beginning at one side and working your way to the other to ensure a straight, bump-free seal.
Measure the sill and cut a piece of weather seal to this length. Peel away the paper backing from the cut strip of weather seal and position it sticky side down on the sill. Make sure the strip is positioned at the point where the window frame contacts the sill when it is closed.
Press the seal against the sill beginning at one side and working your way to the other to ensure a straight, bump free seal.
Measure the inner right and left sides of the frame between the bottom of the open window and the sill. Cut a piece of weather seal to fit each side.
Peel the paper backing from each cut strip of weather seal and press these to the inner sides of the frame. Work from the top to the bottom, making sure there are no bumps in the seal.
Install your air conditioner and pull the accordion panels on each side out until they touch the frame on each side and secure them in place.
Check that the unit fits snugly against the seal and that there are no gaps between the unit and the seal where air might escape.
Measure the width of top of the window once the air conditioner is installed and cut a piece of weather seal to this length.
Peel the paper backing from the cut piece and press the seal to the opening between the stationary part of your window and the top of the frame. This will prevent air from flowing through the narrow gap between the two panes.
Patch areas where you see gaps between the seal and the unit or the window by measuring the gap and cutting a strip of seal to that size. Press these pieces over the gaps to plug them.
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