Window Weight Cavity

mferguson0414

So for a little history on my situation I will start with my home is 112 years old and I have been trying reduce the amount of road noise in my home. I started in 2007 with vinyl windows and this past month we did injected foam in the walls.

With both projects I was really expecting to notice the level of road noise in my home reduced. I chalked up the windows not being a big reducer because the walls had no insulation. Once the insulation was in the walls and the house was still noisy I started to go a little crazy. I scoured the internet for information on what it might be. I read somewhere about how important it is to insulate around windows when they are installed so I set out to see if the installers did just that.

This picture is from the dining room that is on the street side of the house.



The EMPTY cavity is 3 3/4" wide and 5 1/2" deep. My dad guesses that the installers did not remove the exterior trim that was between the old wood windows to fill this cavity and remove the window weights that they cut off. My plan of attack for this cavity and another one like it is to put two different layers of 2" foam with a 1.5" gap between them. The first one tight to the exterior and the second one flush to the interior portion of the window frame. A question I have is do you think I should use great stuff window foam to seal up the exterior edges before I push in my 2" foam or should I caulk it somehow? My dad thinks that caulk will probably not stick to the old wood and that it may just fall. I was thinking of just applying caulk to the edges of my foam board before installing and allow it to smear as I push it in and seal it up that way. In theory this process should get me to a R20 if I buy the right 2" foam board, but I just want to make sure I seal up any air leaks and not mess up the function of the windows with the wrong foam or sealant.

Now the second part of my question is on the sides of my windows there will be another cavity for the old window weights. Does anyone know what size that cavity might be? I know it will be a lot of work taking down all this trim to fill it with foam boards, but I think it would be cheaper than buying slow rise spray foam and injecting it into the cavities.

I am going to try and do one window a month which will include taking off the trim and filling the cavity with the foam boards and cleaning up the trim and repainting. Any suggestions or other questions are welcomed.

HomeSealed

The easiest (and still effective) way would be to fill the cavities with loose fiberglass. Since you'll have them exposed, a layer of spray foam is a good idea, then fill the remaining gap with fiberglass. Sealing those up will no doubt be a benefit for energy efficiency, and may help with the sound as well. The quality and installation of those vinyl replacements may have more to do with the sound though.
The original installers probably did nothing wrong contracturally by not filling those voids, although it is an extra cost that I highly recommend.

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Windows on Wash

+1 on all accounts. Good post.

We do fill those voids but at an added cost. We foam them back but foam isn't cheap so it is detailed out to the customer about what we are doing.

Spray them and fill them.

You will be good to go after that.

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wewantutopia

This is what I did between my windows just like yours (in fact I've done my whole house like this between the studs instead of fiberglass). Just remember to leave a 1/4 - 1/2" gap on all sides of the rigid foam to allow room for the spray foam.

You could go with 1 1/2 inch foam and add 3 pieces in there (I'm sure you'll have a ton left after you cut 2 strips. The whole board will be cheaper then too).

Also, if you go this route get the WINDOW AND DOOR spray foam so the pressure of the regular expanding foam doesn't bow the windows!!!

The Great Stuff window and door foam is in the blue can.

After you foam it in allow it to dry. Then you can cut off the foam that has protruded past the wall with a retractable break away knife (the easiest I've found) so it is flush to reinstall the trim.

mferguson0414

Does anyone have any idea what type of cavity is on the sides of a single window? If this cavity is 3.75" wide, will the other ones be about 2" wide and just as deep(5.5").

Also, what material are those window weights made of? Is it a material that can be recycled for $$.

wewantutopia

It is quite possible just a normal stud bay.

mferguson0414

Should I do a google search for the size of a "normal stud bay"? I was thinking it would have some large cavity that needs filled because of the rope weight that would be on either side of the window. Sorry for my lack of knowledge.

HomeSealed

It is not a normal stud bay. It is an enclosed pocket for the weights, and should be similar in size to the one in the center. mferguson, you are not the one with a lack of knowledge on this thread, kudos to you for asking questions instead of posting bad info as others do from time to time. Secondly, I would not be concerned with over expansion of the foam. The 3/4 thick (or more) wood frame will be more than adequate to protect the window from bowing considering that you are merely spraying a layer of it to create an air-seal, rather than filling the cavity up solid.
The foam/fiberglass combination is going to be easier, cheaper, and equally as effective as cutting up a bunch of rigid board.

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wewantutopia

Sorry. I just meant that you may open it up and find nothing other than the usual ~14.5" space between 16" on center studs and no weights.

I don't really know what's back there.

Are you sure the weight/string/pulley system wasn't in the frames that the installers removed?

mferguson0414

I don't know that I'm following you when you asked the question about the weights in the frames. Last night when I pulled off that trim the weights were laying in the bottom of that pocket with the ropes cut off cleanly.

Tom Struble

don't forget under the sill and at the head

mferguson0414

I will have to take the fiberglass into consideration when I am out shopping this weekend for what to do with the first window that I am tearing into.

I too thought that the Great Stuff window and door would be just fine for this application. Do you know if there is any way to use a can of that spray partially and then clean it somehow to use later? I don't necessarily want to use a whole can of that per window.

mferguson0414

Good point with the sill. The header seems to have a 1.5" gap to the header board that I plan on filling with the great stuff window foam and roxall because of the tight area.

Do you have any suggestions on getting to the sill?

Tom Struble

maybe an apron you can remove?

HomeSealed

The weights would not have been removed during window installation.
Please don't take this the wrong way, but it is probably better not to comment on topics if you really don't know. I have done plenty of electrical and plumbing work in my life, but you won't see me posting over in those forums because the last thing that I want to do is give someone inaccurate information or just "guess"... Just something to keep in mind.

mferguson, you'll want to take the trim off all four sides and address all gaps and cavities. The weight pockets will likely be larger, where the head and sill will be smaller and you can likely fill them with foam alone. On the great stuff cans, you can generally use them a few times within a short period, but I don't know anyway of extending a partially used can for longer than that. Someone else may have an idea, as we use the professional gun with a screw on can for exactly that reason.

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