Insulating window weight cavities

10 years ago

So my wife recently got a job working from home, which means I needed to get on making our little office space more liveable. It was hot in the summer and cold in the winter (kinda like the rest of our 1910 'colonial', only moreso). The little office was part of an old addition (the foundation for the addition was field stone, same as the rest of the house). The old drywall had a layer of paper, paint on the paper, a layer of paper, a layer paper, in that order. Some of the windows had leaked at some point as well, and there was some surface mold under the top layer of paper. Because of the lack of any insulation, and the generally poor shape the drywall was in (not to mention the layers of paper and paint) I thought it would just be simpler and a nicer finish overall to rip out the old drywall, insulate and re-rock the walls.

I've insulated the cavities where I can, but I'm left with the cavities on either side of 5 windows where the weights hang. Is the prevailing opinion to put a thin layer of foam board behind the weights in each cavity, to at least provide some R value? I don't like the idea of insulating the entire room and then leaving these big voids. I'll be sealing all the air gaps I can, and then caulking the trim and all, but I guess I'd like to put something in there, if I can.

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Comments (9)

renovator8
10 years ago
Do all of the windows need to remain operable?
worthy
10 years ago
Here's howThis Old House'sTom Silva does it. (video)

This post was edited by worthy on Tue, Jan 7, 14 at 17:42
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flyingtim01
Original Author
10 years ago
Renovator8, I guess they don't all need to be operable, but I don't really like the idea of having windows that don't function. Three of the five windows had fallen sash weights, and rather than rehang the weights, the PO had installed those little side clamps that screw into the window, and then rotate on a cam to push against the stop. I suppose I could just remove all the weights and use the clamps, but that just kinda seems hokey to me.

Worthy, thanks for the link. I don't think I would have ever thought of that trick for getting a piece of foam stuffed in around the rope hole - that's pretty darn slick. Do you think there is any benefit over using the foil faced foam, instead of unfaced? I think I have a sheet of unfaced foam leftover.

Part of me is thinking that anything I do in this previously un-insulated room is better than where it was, but I'm fighting that feeling, I want to do this one right before it all gets sealed up.
snoonyb
10 years ago
If you notice, in the video, only the lower sash operates.So if both sash now operate you;ll need to adjust the foam thickness as the weights need a free float to operate correctly.

However, you could remove the weights and fill the cavity with foam, If the windows are still single glazed and are not heavily fabric draped and/or have a storm window installed, you'll have spent a lot of time, for little results.
worthy
10 years ago
Unfaced foam will work fine.

Instead of rehanging the weights, you can use historically accurate counterbalance springs.

The materials cost is low and you're opening the area anyway. Sealing a house is the sum of a lot of small measures that in themselves may not be that significant. But they add up. In lieu of adding storms? No.
flyingtim01
Original Author
10 years ago
Thanks Worthy - I didn't even know those spring balances existed, let alone were period-correct. Seems like that would be the way to go. I'd eliminate the weights, the chances of ropes breaking, that charming clunking every time you open or close a window, and I could seal each cavity completely. Looks like there will be a little bit of work (perhaps) to mortise the sides of the sashes, but the finished product will be nicer, looks like.

As for storms, I do indeed have them. I resealed them just before our house got painted in September, but I noticed once the cavities were opened up that there was still a small leak I need to attend to. Plus, there are some other air gaps in the cavities where I can see daylight from the inside looking out.
sombreuil_mongrel
10 years ago
Hi,
You can remove the weights and substitute Caldwell Tape Balances (or Pullmans) and completely insulate the cavities, retaining full window function; spray foam may be best. Be advised that doing so often results in rot at the sill; the air movement you have now allows the water that enters to dry out freely.
Casey
igloochic
10 years ago
I was just in a vic being restored and they did the most lovely thing....the weights and chains are all tucked into a plastic plumbing pipe and then they could tuck in all the insulation they want to without bothering the workings. They split the pipe and then duct taped it back together after tucking the back half around the weights. We will likely do this with all of our windows. Everything is hidden once you put the frames back on the windows, and they all work, which, like you, I find very important, both for myself and for future resale.
flyingtim01
Original Author
10 years ago
Casey, thanks for the info. I've read somewhere about leaving weep holes in the bottom on the storms to the sills can drain and not accumulate moisture and rot. Or did you mean rot at the sill plate at the base of the wall? I feel like as long as I spend some time really sealing that wall up from the outside at the storms and the window frames, I shouldn't get enough moisture in there to have to worry about rot, unless I'm wrong, which is entirely possible.