How to seal and insulate an enclosed rim joist in an older balloon frame house?
Howdy,
I hope you don’t mind my asking this question here. I’ve talked with a number of contractors and gotten different answers from each.
I recently moved into a 1930s balloon framed home in Maryland. The ground floor is quite cold in the winter, and I’m getting ready for next season. The walls are insulated with fiberglass batts; the attic has blown fiberglass to R-40 (but I don’t know the extent of the air sealing in the attic, though my suspicion is that it is not sealed).
In the unfinished, uninsulated basement, the rim joists are enclosed. There’s a vertical board at the end of the floor joists, with a four inch space between them and the exterior of the house. (See illustration at http://upload.wikimedia.org/wikipedia/commons/thumb/8/89/Balloon_frame.jpg/300px-Balloon_frame.jpg )
The wall insulation does not extend all the way down to the basement. So, there’s a 6-inch gap that’s totally enclosed by walls and the “built up sill” as illustrated in the JPEG above. Insulating the “rim joist” from the inside of the basement will do nothing to seal the bottom of the wall cavity. Cold air will still pour in from the actual exterior wall and stack-effect its way right up the wall cavity.
I’m debating:
– Insulating the basement ceiling and “rim joist” anyway and doing nothing about the enclosed open space
– Drilling holes in the “built up sill” from the basement, and injecting fire-retardant spray foam as best I can
– Hiring a contractor to blow dense packed cellulose in that space all the way around the house
Moreover, it’s been very tough to find an insulation contractor that will take the time to understand what’s happening in the house and help solve the problem.
I would be grateful for any advice. I’ve been around and around on this for a few months now.
Thanks,
Joe
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Replies
Joe don't try to seal up an old home as if it were a new home unless you plan to install additional mechanicals to ward off the IAQ and IEQ problems which follow. If your real concern is fire blocking this can be achieved with minimal cost and a lot of sweat if your a handy DIY'er.
Insulating from the sill (a minimum of 12 inches) into the basement will help with perimeter air infiltration using mineral wool, glass fiber or cellulose. Spray foam is NOT a fix all solution as tempting as it may seem. It's also hazardous to your health if you do not take the proper precautions as outlined in this link..
http://www.epa.gov/dfe/pubs/projects/spf/exposure_potential.html
Many old homes (1800's to early 1900's) built with balloon framing also have solid sills typically 6 inch x 6 inch.
Stack effect occurs even in modern construction. This link may help you with understanding "Stack Effect" and there's many helpful resources in their library of publications.
http://www.buildingscience.com/glossary/stackeffect
You may consider hiring a contractor registered with LEED to examine your home as an independent consultant.
http://www.usgbc.org/leed
http://www.green-buildings.com/experts
Richard,
In New England, we have lots of skilled weatherization contractors familiar with problems like this. The usual solution is to drill access holes and fill the volume with dense-packed cellulose. Hopefully, you'll be able to find a cellulose contractor who can help you.
As long as that interior-side band joist is accessible it's a dead-easy job to drill & fill with 3lb dense-packed cellulose or 1.8lb fiberglass, which would tighten up the bottom of the wall considerably.
Injecting slow rise foam or injection foam in there won't necessarily seal as well as dense packed fiber, which flows toward the leak paths during installation until those paths are so clogged it can't. Injection foam would have a similar characteristic during installation, but will shrink as it cures, whereas dense-packed fiber is under some amount of springy tension. Slow rise polyurethane may work, but it may also have adhesion issues depending on how much surface grunge there is (and you don't really get to see it), and you have to be careful to put in enough for a complete fill, but not so much that it creates a blow-out or distorts the planking.
If it's a poured concrete foundation it can be cheaper, tighter, and more reliable to seal the foundation sill with can-foam and insulate the foundation from the interior rather than insulating between the floor joists. The floor typically has 1001 electrical/plumbing/flue penetrations to air seal which can be difficult to do a great job on whereas the foundation walls are more accessible, flatter, with fewer penetrations to deal with. Even if you only insulated down to a couple feet below grade the thermal benefits are huge.
Thank you all -- that makes good sense and I'll focus on dense packed cellulose. I appreciate your help! Have a warm winter!