Insulating Window Weight Pockets

Use a hammer and pry bar to carefully remove the wood trim from around the inside of the window exposing the sash weight pockets.

Insulating window weight pockets.

Then cut strips of 2 foam board to fit into the wieght pocket where the weights used to be. If there is a gap i would caulk it. Use foil tape to seal the joint between the window jamb and foam insulation. Insulating window weight pockets i am not 100 sure that just removing the casing will reveal the cavity.

Stack strips to completely fill the void. These houses typically have no water management details around windows doors which works while the wall is open but will cause issues with insulation. Cut strips of foil faced rigid foam insulation to fit into the weight pockets. Check the fit of the brick molding.

This old house general contractor tom silva shows an energy efficient way to insulate old windows. I did this on several windows. I restore these windows for a living. For window weight pockets i just blow out as much dust as possible then spray the area with water then canned foam the cavity.

I would not try to fill in the weight pockets with any insulation. We use a router to grove the sides of the sash so that the sash can move along an interlocking metal track. It may be be covered with lath and plaster as well which would open up another can of worms. Remove sash weights for upper sash the ones closest to exterior wall and replace pulleys with the pullman device that fits into the pulley hole.