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Double-hung windows can be more challenging to seal than other types, such as casements, because of their two sliding sashes. Follow the instructions below for weatherstripping wood double-hung windows.
Scrape off chipping or loose paint and remove worn-out preexisting weatherstripping (if there is any). Also make sure that the sash lock is properly positioned to pull the upper and lower sashes together for a tight seal. If not, reposition it.
Measure the length of the channels between the sashes and the window jamb, and cut the weatherstripping to the appropriate size. To do this, open the lower sash and insert a strip on the left side of the window up between the jamb and sash. Make a mark where the strip hits the window seat, and cut the strip at this point. Do the same thing on the right side of the window. Follow these directions for the upper sash, as well.
Reinsert the strips between the sashes and jambs, making sure the nailing flange abuts the stop, and nail them into place. Open and close each sash to make sure you have a good seal. If necessary, you can pry a strip slightly upward using a putty knife to ensure that the sash compresses it.
Lay a strip along the horizontal length of the window and cut it to size. Cut two more strips to the same length.
Install one horizontal strip across the bottom of the lower sash and another across the top edge of the upper sash. Be sure the nailing flange sits evenly with the window’s inner edge, and nail in the strips, being careful not to pound too hard (you could break the window). Affix the third strip to the base of the upper sash. If necessary, you can pry the strips up slightly as mentioned in Step 3.
As a final step, you can add window pulley seals, self-adhesive caps that cover the pulley area and stop drafts. Simply clean and dry the area, and stick these in place.
To read more about spring-style weatherstripping installation, see “How to Install Window Weatherstripping.”
