Hello,

I am remodeling a 1940's two family with original windows. Most of the window folks I have gotten quotes from offer only to insulate the hollow window pockets by shoving in fiberglass insulation. I feel like that is pointless because the insulation is only going to serve as an air filter with no vapor barrier or insulating value. After some searching online I found the best practice to be removing the trim and insulating the weight pockets with Tuff-r rigid foam insulation. Now that I have begun the process of removing the trim I am finding it to be perhaps more work than it is worth. The lath and plaster is flush with the window rough opening. Which means I have to cut away the lathe and plaster to access the pocket.

So, do I bother to do this with every window? Is there an alternative like dense packing cellulose?

Any help is greatly appreciated.

Can you get an expanding foam spray can nozzle in the cavity? Maybe drill some 1/4" holes into the cavity behind the trim to allow insertion of the nozzle?  If you can get the nozzle access, just shoot some low expansion foam for doors and windows in there.

http://building.dow.com/na/en/produ...owdoor.htm

I was thinking of that but with each bottle costing around 12 dollars I'm concerned with the cost.

Posted By GreenThumb on 03 Jan 2015 05:00 PM
I was thinking of that but with each bottle costing around 12 dollars I'm concerned with the cost.

A 12 oz can of that stuff is <$5 at the local Wal-Mart and around $5.50 at the local Lowes.

I concur with arkie6. Spray foam would be your best option.

The window pockets are  2.25w x 4d x 65h and there are 72 of them. 

How do I really know the foam filled the entire cavity without doing an IR test?

You have 36 windows that are 65" high? And it has original windows? Single pane I assume? Are you replacing these windows with more efficient windows?

Filling the cavities with cellulose would be an option if you can get a big enough hole to access the cavity. Can you drill a 1-1/2" to 2" hole behind the trim? If so, filing the cavity with cellulose might be an option. Are you planning to do this yourself or hire someone to do it? An insulation contractor with the right equipment should be able to dense pack the cellulose, but DIY would be difficult using the free loaner cellulose blowing machines from the big box stores. Without dense packing the cellulose, you might end up with some settlement over time, but it would have to be way better than the currently open cavity. You might install the hole at the very top of the cavity and then fill/pack with cellulose as best you can, then as a final measure fill the very top of the cavity and hole with Great Stuff expanding foam. As the foam expands it would further pack the foam and seal the fill hole. Trim off the excess foam after it cures and re-install the trim.

The windows themselves are only 58" but the pocket goes up a few inches on the top and bottom. Yes they are single pane. I am replacing the windows with Harvey Acoustic or streamline medium solar gain replacements. I have pictures but they are to large to post here. Thank you for the advice btw.

there is usually a removable panel for access into the weight cavity, used to replace the weights or the rope. You can use this to access for foam or cellulose.

Here is a picture from my first trial window.

I've been doing this for 30 years with my replacement window business. The only real way to fill a ballast chamber is with cellulose insulation. Fiberglass bats will hang up on the lath and nails, puf will not expand in a uniform way since it is a great adhesive. So the only way to do a good job is celly. You can get a machine from the Homarama that while underpowered for sidewall applications will probably do the job if you cut the material slide down to a small opening. You can buy a 5/8" brick nozzle from a company like JR PRODUCTS INC, drill a 3/4" hole and install. Since the hole is small drill one at the top and bottom of each side ballast. If you set the machine up right you may be able to do one hole on each side casing . You can get tapered wood plugs from JR to fill the holes or use my favorite wood filler Bondo.

Just saw the picture. Use celly and leave the casing on. You'll regret taking them off since they never go back on the way they came off and it's easier to fill with cellulose with the chamber sealed. Also you'll have less of a mess as far as lead paint is concerned which is what you have according to the picture that you posted.

Also you have a space under the sill and between the head jam and the framing so taking the casing off won't cover everything unless you remove all trim A time consuming and messy job that will compromise the plaster. I've had plenty of customers choose this method and regretted it.

As far as the space under the sill and over the head jamb should I drill holes and foam it? Also, do I need to be concerned about not having a vapor barrier with the cellulose?

Drill holes and cellulose the openings. I wouldn't use foam too much stick and not enough flow. Depending on the way the windows were built. When you blow the sides you may fill the top and bottom at the same time. This style window was installed similar to new construction windows of today. The window was installed in the rough opening, leveled, plumbed then nailed thru the exterior casing with the interior trim being the extra support. I usually install the celly in the chambers after the window is installed and caulked. The celly will blow around the window itself from cracks in the jamb. No vapor barrier is needed.

Hey, all ended up just using foam. I used a ir test to make sure I had full coverage. Tried using the cellulose but the machine I got from the box store was garbage and not worth the trouble. Ended up returning the cellulose and just foamed. Happy with the results not to happy about the cost though. I found out just how leaky my window assembly is too. My neighbors asked me if my house had a cold. I looked at them funny then they pointed to the side of the house and under the sill foam was bubbling out.