Replies

1. GBA Editor
   Martin Holladay|Jun 03, 2016 05:31am|#1

   Elizabeth,
   If your windows are being restored rather than replaced, there really isn't any opportunity for adding insulation, assuming that the original sash weights are being reused.

   The reason is that when old windows are restored, the window frame usually isn't removed. It stays in place. Although you wrote that the windows will be "taken to the workshop for several weeks," I'll bet that only the sash are removed, not the entire window.

   If the sash weights are being replaced by new balancing hardware, then the sash weight pockets should be filled with spray foam.

   Hopefully, the window restoration will include new weatherstripping.

   If your walls are uninsulated, you could, of course, hire a weatherization contractor to fill your stud cavities with dense-packed cellulose. But that type of work is usually separate from a window restoration job.

2. 
   CL|Jun 05, 2016 05:52pm|#2

   In a 1920's house with wood double hung windows, I did the following, which seems to have worked:
   1. Remove the parting strip on the window sashes. This will let you remove the windows from the frame, and remove the rope from the wood frame. At this point you can tie knots in the rope to prevent the weights from falling into the wall. You will notice a draft coming through where the rope goes over the roller from the cavity.
   2. Remove the interior trim on both sides / jambs
   3. This will expose the weight cavities and allow you to remove the weights from the rope
   4. I installed 1" rigid insulation against the outside wall of both weight cavities, "tacking" it in place with expanding spray foam.
   5. I then cut lengths of PVC pipe that was big enough for the weights to fit in easily. I cut this at a 45 top and bottom. I attached the pipes to the framing at the top and bottom just screwing through the piece exposed by the 45 cut. MAKE SURE the rope does not rub on any part of the pipe - that would wear it out. Try to get the pipe as close to the roller as you can, so that when the weight is at the top it is in the pipe.
   6. After I had 2 pipes in each side, I measured the lowest point of the weight to make sure it was still inside the pvc, then sealed the end of the pvc with spray foam. Then I built a box out of 1" rigid between the rope roller and the PVC and sealed that all up. Now the air inside the pvc pipe is isolated from the weight pocket and is part of the house.
   7. Then install fiberglass batts inside the void and around the PVC pipe.

   The above is obviously far too involved to have done by someone else, but it is a simple DIY project, one window at a time. It drastically cut down on drafts.