Insulation question for old solid brick house
I am working on a project in Toronto and we are renovating an old brick house to bring it up to code. All the plaster and lathe has been ripped out and we are preparing to insulate the exterior walls and I would appreciate any input on the following strategy. The house is triple brick to the first floor joists then double the rest of the way. The house was built in 1919 and the brickwork looks solid.
My plan for insulation was to first, fasten DUROSPAN GPS R5 4 ft. x 8 ft. x 1.06-inch Graphite-Enhanced Expandable Polystyrene Insulation Board to the brick with construction adhesive and seal with tuck tape (R5). Next, I will construct a 2×4 stud wall overtop of the foam for electrical, plumbing, ductwork, etc. Finally, I will fill the stud wall with sprayed-on cellulose insulation (R12.3) and 1/2″ drywall (R.45). Add the two courses of brick (R.88) and my total R value will be 18.63.
Using spray foam exclusively for the exterior walls seems to be very expensive, though we will be using it for certain areas in the building. I would appreciate any thoughts you folks can throw my way.
Richard
Replies
I have a similar (1927) house. I live in climate zone 5, Chicagoland. I've thought about this a lot.
Take this with a grain of salt. I'm not a professional but I work maintaining similar age industrial buildings.
Masonry absorbs water. Any water that gets into the bricks or mortar is now designed to be put into the air due to the bricks not freezing. If you insulate behind the brick, the bricks can freeze. This will destroy the masonry.
I think there might be a was to do this, but I'm not smart enough to figure it out. In all my projects, I'll never insulate behind the masonry. I just want to be safe. It may cost more to heat, but it won't fall down.
I agree with Bon's remarks regarding the moisture issue but I am pretty sure you can safely insulate the interior of old brick buildings and after checking out Building Science Corporation, I think my method detailed above is acceptable. The most highly recommended way, according to BSC, is to use 1" of closed-cell spray foam directly on the brick and then stud wall with wood and then use sprayed in cellulose to fill stud wall. Polystyrene panels, while being better R-wise, are more trouble to install as you have to have to seal all the panels with either tape or spray foam because there must be NO air space between brick and warm side. Check out this excellent paper BSC created: https://www.buildingscience.com/file/5801
Thank you for adding to my knowledge.
This still would scare the snot out of me. But I'm a belt and suspenders type of guy. There seem to be a lot of concerns even in the paper.
I'm gonna stick with my leaky house.
I had a brick on block house and used insofast.com to insulate the walls. Fast and easy. Attached drywall directly to the product. Check it out.