Insulating and protecting an existing brick wall
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| Posted in GBA Pro Help on
We are renovating our 100+ year old house room by room. We realize the most common and effective way to insulate is with spray foam (our brick is in excellent condition with no apparent water damage). Our problem is that because we are doing the renovations room by room, spray foam is not the most cost effective way to insulate. I can’t seem to find any mention of using rigid insulation in previous articles. Can anyone make suggestions as to how to insulate with rigid (IE are vapour / air barriers required when insulating against the existing brick) and if it will do more harm than good?
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Replies
Amy,
Because of thermal bridging through the brick wall, it really isn't possible to achieve much energy savings when you only insulate one room at a time.
To answer your question: the best way to insulate a brick house using rigid foam is to cover the exterior of the walls with rigid foam, followed by synthetic stucco.
For more information, see Insulating Old Brick Buildings.
Hi Martin,
Thanks for your input, we have no choice but to go room by room. We are looking to insulate from the interior rather than exterior as we do not want to cover the existing brick (even though we realize this is the best solution of all). Thanks for the reference to the article. I had already stumbled across it and found it very informative, but it had no reference to insulating with rigid from the interior. Because the rigid does not hold moisture as the batt would, I'm wondering if it's an ok alternative to the spray foam....
Amy,
I really have nothing to add to the advice in the article.
Insulating a brick building is tricky, so proceed with caution. Pay attention to all of the factors listed in the article before proceeding. If you are sure you want to insulate on the interior, the best insulation product to use is closed-cell spray polyurethane foam.
If you're going room by room, and are worried about the contractors making multiple trips, perhaps look at DIY foam kits such as DOW froth packs. Your local lumberyard should be able to get them. 1ft2 1 inch thick is 1 board foot. IIRC, they run about $1/ board foot
If you want to use sheet foam then use XPS foam (i.e., closed cell) attached to the wall with spray foam adhesive or PL polyurethane. Seal all gaps with spray foam or Tyvek tape or a Dow tape specifically made for use on foam.
No one asked the first question, which is where are you located? This will help determine freeze/thaw issues and the thickness of the foam.
Billy
Ottawa Canada.....so freeze thaw could be an issue. But we have no evidence of water damage to our brick and it is in very good condition. Thank you so much for suggestions. Both responses give alot of food for thought. We had considered both applications and circled back to your comment Billy, about freeze thaw.
Amy,
Congratulations on tackling such a big job. If your masonry is anything like what we see here in Ohio, they are quite uneven and rough with lots of holes and lots of air infiltration. Closed cell spray foam is absolutely the way to go. Talk to your local contractors first - chances are that you can find one who is willing to work with you as long as you are flexible about your schedule. Your best bet is a small company where the owner is also the installer. If that doesn't work, the foam kits that Aaron mentioned above will also do the job.
I agree, closed cell spray foam is best. You'll want it thick in Ottawa.
Because the brick cannot dry to the inside it will hold more water, and because it will not be warmed from the inside (because of the foam insulation) freezing water inside the brick could compromise your wall. Just so you know this is a potential risk... but I would go ahead and spray the foam if it were me.
Billy