Insulating sash weight pockets
NotaClue
| Posted in Energy, Heating & Insulation on
What do you think is the best way to insulate sash weight pockets on working double hung windows?
1) PVC pipe the weights and foam in around them
2) cut dual foil faced XPS to fit each pocket and slip in into the slots flush to the frame
3) other.
The trick seems to be doing this work WORKING double hung sashes; if they were coming out, then it seems trivial; you use a non/low expanding foam and fill in the pockets; but they’re not and the weights will need to work.
clues?
Thanks
NotaClue
Replies
Either choice works well, but the most important step is to seal all of the gaps. And also insulate the space between the window and what passed for headers in old houses.
...that's not a mistake, it's rustic
I'm facing the same situation and have been looking at it for a whil. Yours may be different, but my weights don't really fit well in the PVC and I'm concerned about a snug fit and the weight getting wedged in there.
I'm considering a couple things:
1) Taking some round ducting and making it the right size to accommodate the weight and using foam around/behind it.
2) Having some sheet metal bent into a U shape with flat edges on each side, then putting that behind the outer weight and foaming behind it. That would leave me access to the weight from inside. I would then probably put some poly board on the inside if possible.
I'm really hesitant to trust that I'll never have to get into those weight pockets again.
Just my two cents.
As a practical matter, I don't think it is possible to insulate the cavity -- and keep the weights operable -- and maintain access so you can change the sash cords when they break.
There are various systems (e.g. using the plastic track, that I'm sure you've seen) that can be used to retrofit your existing windows. But the windows have to be cut down, a groove routed in -- generally not a diy project. There are guys in most metro communities that make a business out of these kind of refits.
I'm sorry I don't have a link for you, but there is a company called Blaine (Window Hardware, I think) that make a couple of products you can use in place of the sash weights --e.g. spring balances, etc.
********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Here is the Blaine link that will take you to "spring balances." Unfortunately, there is no description, only a pic.
http://www.blainewindow.com/catalog/itemlist.cfm?catid=89&compid=1&pcatid=15
********************************************************
"I tend to live in the past because most of my life is there."
-- Herb Caen (1916-1997)
Could you use two or three strips of xps, one on the inside of the sheathing, one glued in the middle of the pocket as a divider between the two weights (fairly tight and glued in with PL300) and one strip flush with the wall surface that the casing goes over.
If you lack space, the thin varieties are available that are usually stapled on the outside of old houses before vinyl siding. This would result in a baffled space with two dead air spaces.
Whoa....this is a topic I invested some time in when we had all our old bays open.
Irrespective of whether you replaced the sash cord with a metal replacement, the question of accessibility always comes up. Thus, whatever you do, make sure that you can still access the weights via the side door in the frame if a sash cord breaks.
The only solution that has made sense to me is to glue/seal a thin sheet of high-R insulation to the inner face of the outside board in a sash pocket. I forget the name of the stuff... Isocyanureate or whatever the R-8/inch the stuff is. Alternatively, go for a aerogel insulator for R20/inch goodness... at a premium price, naturally.
In the end, we didn't insulate anything, simply sealing the seams with silicone and hoping for the best. So far, our infiltration rates are superb. However, I think there is a real business opportunity for someone with the cohones to offer a slim, DU-based weight replacement system that can allow much smaller weights and hence allow the filling out of that space with insulation.
If it's good enough for the ammo of A10's, the keels of racing yachts, and the like, why not double-hung windows?
what is DU, pls?
DU = Depeated Uranium = Radioactive Sash Weights
Depleted Uranium. Incredibly dense, so much mass in little volume. It's used for armor piercing shells in things like the M1A1 Abrams MBT (main battle tank)
Depleted Uranium... it's not very radioactive as some replies might indicate, but very hard, very dense stuff. Because it's denser than lead and gold, it makes an ideal material for things like boat keels on competition yachts because less frictional surface area below the surface = a faster ship. The US has tons of the stuff lying around, as typically less than 1% of the Uranium mined for reactors and bombs is U235 (radioactive) instead of U238 (mostly inert). That's why it makes for an excellent tank penetrating shell and the like... a great way to dispose of the U238!
Ok, short of having radioactive window weights, I think I'm hearing a consensus that XPS with caulk is what's going to be the best compromise.
DU!? Hey, if you cut it, to balance weight for a window, you've just created a trail of radioactive dust; I'd hate to breath or ingest that!
NotaClue
The idea is that you let someone else fabricate the stuff for you, i.e. someone who knows what he/she is doing. I wouldn't ask just anyone to machine beryllium either and that stuff isn't radioactive (but produces very toxic dust). You could even lead-dip the weights to ensure that whatever is inside the DU stays in there. Anyway, the suggestion was really a tongue-in-cheek suggestion. I doubt many people besides yacht racing consortia and the military could afford to deal with the stuff. For us mere mortals, regular lead usually does the trick. My sash pockets probably could have accomodated PVC piping for the weights to slide in. Then there is the "simple" matter of creating the kinds of interfaces at the top and bottom of the pipe to accomodate the spindle at the top and the service window at the bottom. I.e. the weights should remain servicable... so the PVC pipe cannot be very snug around the weight.
True DU is not a big radiation hazard. It's radioactive emissions are reduced to about 60% of the non-depleted Uranium (primarily due to the reduction in U-235 from 0.7% to 0.2%). Most Uranium decay produces weak alpha radiation which can be attenuated (blocked) by a single piece of paper. This decay chain is what produces Radon and ultimately lead. DU sash weights would eventually go out of balance because in about 8 billion years most of the U-238 will have turned into Lead-207. So you would end up with lead sash weights after all. Actually by then the sun will have turned into a red giant with a girth sufficient to engulf the earth...so it won't matter that your sash wieghts have lost two pounds. DU is more of a hazard as a heavy metal (with similar toxicity to lead).If you want exotic, high density, sash weights...tungsten would be a better choice. Tungten alloy densities can equal that of DU, and are often substituted for lead and other heavy metals. Tungsten is also non-toxic.
Honey... you are so cute. How DO you remember all of those numbers and big words? You are my favorite recovering science teacher. Congratulations on the successful business. Love, Your Wife
Edited 5/29/2005 11:14 am ET by basswood
"DU sash weights would eventually go out of balance because in about 8 billion years most of the U-238 will have turned into Lead-207. So you would end up with lead sash weights after all. Actually by then the sun will have turned into a red giant with a girth sufficient to engulf the earth...so it won't matter that your sash wieghts have lost two pounds."Well, this remodel is supposed to last until the end of time--that's why we used old growth redwood to rebuild the window sashes; so 8 billion years just isn't going to make it.NotaClue
I got this in a recent thread about replacing weights:
http://www.pullmanmfg.com/
It's a spring loaded system designed fit into the existing pulley slots. I don't know how it performs, or lasts (if it's anything like a tape measure, probably not as long as a new sash cord). I'm guessing there's no maintainance, just easy replacement.
I'll always like the weights, but with this you could insulate the cavities completely.
Just a thought about future access in the PVC case. If you replace the sash cord with metal sash chain, that should be good for at least a couple of centuries.
I did this on several windows. Remove exterior flat casing to reveal weight pocket. 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. Then cut strips of 2" foam board to fit into the wieght pocket where the weights used to be. This leaves plenty of room for the weights for the lower sash to operate. Caulk or foam any gaps where the foam board fits into the weight pocket, cover it with typar or similar sticky flashing, and reinstall casing. Replace lower sash ropes with brass chain because it looks good. Because the upper sash is up most of the time, you don't see the Pullman gizmo, which is not particularly attractive. This completely eliminated the bad drafts coming thru the pulley openings. BTW, I coulndn't do this from the inside because the weight pockets were covered by the rock lathe and plaster.