Insulating brick with 3/4 strapping - Contractor Talk - Professional Construction and Remodeling Forum

downwithfloors · 10-28-2008, 04:24 PM

Hey insulation gurus.

I am a flooring guy, so excuse what I guess is a common question....
My exterior walls are double brick, and I believe there's an air pocket 'tween 'em. I'm ripping out my lath and plaster inside to insulate, and found 3/4" strapping attached at random lengths (almost 16") to the inner layer of brick. I have 3 questions:

a) Should I bother?

b) Is 3/4 Styrofoam insulation enough with a vapor barrier and drywall?

c) How would you insulate given this scenario?

One contractor recommended wrapping the inner brick with Tyvek, attach 2X4's flat at 16" using Tapcons, rigid insulation (1 1/2"), vapor barrier, and drywall. Sound good? Help, I'm doing the demo now...

Thanks in advance,
Ian,
floorguy.

SLSTech · 10-28-2008, 06:41 PM

Let me get this straight - first you double post this
Second all your posts are asking for help or questioning the way something looks in the flooring section & your a flooring dude.
Then the worst thing you do is bring in a contractor to do an "Estimate" I would guess & question what he said?
I may have it wrong but it appears you probably should be in the DIY forum. Thanks for playing

downwithfloors · 10-29-2008, 07:35 AM

Thanks for the positive response pal. That's what we're here for, right. Double post for the opinion of both drywall and insulation professionals. The "contractor" was my uncle from out of town over the phone offering his help. If anyone has any positive advice, I'd much appreciate it.

Thanks...

Ivinni · 10-29-2008, 10:20 AM

Start with deciding what R-Value you would like to have. I see you are in Toronto, so I bet you would like as much as is possible.

I do not know what you mean by "strapping" and what it means to your insulation efforts.

The air pocket will give you an R-1, or there abouts.

Depending on the density, the rigid insulation will vary R-values as well as with thickness.

If you decide on 2x4 fat against the wall, you will restrict the possible R-Value. with an 8lb board (rigid insulation board) you will only get around an R3.5. So with the air pocket, you will have around an R-5. Not very much in my opinion.

I would want a minimum of R-19 if i lived in Toronto. It's been a while since I studied R-values but I think these are close. Hope this helps.

downwithfloors · 10-29-2008, 11:33 AM

Thanks Ivinni,

Ironic getting insulation advice from Florida. I'm considering building a proper 2X4 frame, Tyvek the brick side, highest R value of batt insulation, vapor barrier and drywall. I'm losing some space, but hopefully gaining heat in my living room.

**Cole** · 10-29-2008, 12:05 PM

Quote:

Originally Posted by downwithfloors

Thanks Ivinni,

Ironic getting insulation advice from Florida. I'm considering building a proper 2X4 frame, Tyvek the brick side, highest R value of batt insulation, vapor barrier and drywall. I'm losing some space, but hopefully gaining heat in my living room.

DavidC · 10-29-2008, 12:53 PM

Quote:

Originally Posted by downwithfloors

Thanks Ivinni,

Ironic getting insulation advice from Florida. I'm considering building a proper 2X4 frame, Tyvek the brick side, highest R value of batt insulation, vapor barrier and drywall. I'm losing some space, but hopefully gaining heat in my living room.

This would be my choice. My house is plank construction (no room for insulation) and this is what I'm doing room by room on all exterior walls. If you run a AC unit in the summer use kraft faced instead of a vapor barrier.

Check out www.buildingscience.com for what is the best in your area.

Good Luck
Dave

Jason W · 10-29-2008, 02:38 PM

You should look at doing spray foam for the walls.

You can get up to R7 per inch with it and it can be your vapor barrier as well. Not to mention, it will seal all those little cracks and pin hole in the brick walls.

how's R24 sound?

downwithfloors · 10-29-2008, 02:59 PM

Thanks guys. R-24 sounds great, however... I'd like to maintain the interior brick facing if I can. It's in good shape and may one day decide to expose it. How difficult is it to remove and dispose of sprayed insulation?

Jason W · 10-29-2008, 03:06 PM

Quote:

Originally Posted by downwithfloors

Thanks guys. R-24 sounds great, however... I'd like to maintain the interior brick facing if I can. It's in good shape and may one day decide to expose it. How difficult is it to remove and dispose of sprayed insulation?

It really depends on what you use. A closed cell spray foam would be like putting Gorilla Glue in the cavity but, a medium density open cell foam would clean up with little effort (comparatively).

Are you in a Historic district? They don't really build em' the way you described it anymore.

Jake Stevens · 10-29-2008, 03:17 PM

I would build my 2" X 4" wall with a Radiant Barrier up against the brick and a R13 fiber glass insulation, sheetrock, and that should give you about a total of R23

downwithfloors · 10-29-2008, 05:59 PM

The house was built in '28. Still rock solid with great guts. Just finished all the demo. Going to start the framing tomorrow, while trying to restore the mahogany window trim and base. I like Jake's concept. I have loads of Roxul R-14 in the basement I wanted to get rid of and it saves labor in the long run if I decide to expose the brick when global warming takes it's toll on Canada. Thanks for all the advice.