Insulating Old Windows

[pappster85]

I am in the process of restoring a cluster of three double hung windows. Between each window is a pocket for weights. The weight cavity is covered by 3/4" wood on the exterior and interior. It crossed my mind that maybe I could fit polystyrene sheets on the back of the outside piece of wood. I think it would reduce heat transfer between the inside and outside world. Can anyone think of a reason why I should not do this? Any ideas or opinions would be fantastic.

Thank you!

[mattswabb]

If it doesn't interfere with the weights then it should work. Be sure to check the caulking on the exterior of the window.

[Sashguy]

Careful. If you are in a humid area, this may cause rotting.

[pappster85]

The rotting was my concern. I am in lower Michigan near Detroit. So, I am not sure if it is an issue or not. I pulled the trim off along the bottom of the windows as well. Turns out, there is nothing there between the trim and the brick exterior. Not exactly a big deal so long as the caulk is maintained on the outside of the window. Or so at least I think.

[heartwood]

I would stay away from insulating the pocket...the air transfer (circulation) does more good than harm...mold was a rare issue in decades past but with all the 'buttoning up' it has become a real problem...in most cases of wood to wood , the trim really shouldn't require caulk if the trim is painted...because you have brick/wood contact, you may want to consider sika flex 1a...it comes in many colors and does not require painting...it has better elasticity and can fill a larger gap than conventional caulk...

...jade

[Sashguy]

To bring it home, the general mentality is to turn our homes into Igloo Coolers. Jade and I see the damage resulting from this mindset on a daily basis. Wood cycles from moist to dry on a continuing basis with the only result being minor checking. A break in this cycle can be disastrous.

[phil]

some windows have enough roof overhang that moisture is less of an issue I think , but maybe in Michigan the humidity is an issue, or if you are in an area where windows ice up, what works in Nevada might be a lot different than the maritimes