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Old 08-18-2012, 04:33 AM   #1
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Spray foam the interior of a exterior brick wall?


I have,a 1977 single story all brick house im south texas I need to strip to the studs so I can rewire and replumb. Im new to the idea of spray foam but want to get it installed. the house has a brick pocket with weep holes, soffet and ridgecap. I wanted to add flooring to the attic for storage and have a surface to spray foam the ceiling below. If there is no vapor barrier in the wall do I spray the brick? Or put xps im each stud bay then foam that? Also I wanted to the leave the soffet and ridge cap open for ventalation, but seal the walls and ceiling of the house. Will this cause any issues?

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Old 08-18-2012, 01:03 PM   #2
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Spray foam the interior of a exterior brick wall?


You don't spray the bring in this case.

Brick is very likely a brick veneer wall and is designed to be vented/breathable.

Air barrier is on the wall on the outside surface of the studs. That is where you vapor control layer should be as well.

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Old 08-18-2012, 10:52 PM   #3
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Spray foam the interior of a exterior brick wall?


Demo will start at the end of october. But I couldn t wait so I removed a non working receptical and box. Through the box hole i can see brick and a weep hole. So either the gypson board rotted away or there was never a vapor barrier. Not even tar paper. So when the time comes do I seal the the far side of the wall with foam board and spray 3 inches of 3lbs closed cell foam im the stud bay. Leaving the brickpocket intact.

Does anyone have a picture of how this should look.
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Old 08-19-2012, 08:29 AM   #4
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Spray foam the interior of a exterior brick wall?


If you can get rigid foam to the outside wall, make sure it is the proper vapor permeance for your region.

I think 3" of ccSPF at that point is overkill.

http://www.buildingscience.com/resou..._code_changes/
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Old 08-19-2012, 04:24 PM   #5
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Spray foam the interior of a exterior brick wall?


Another thing you may want to consider is to insulate the bottom of the roof instead of the top of the ceiling. This is called "Hot Deck" and has been proven to be a very effective method that doesn't affect the life of shingles. One big advantage is that it makes future modifications much easier. If you do that either not have to worry about ventilation of the attic area as it becomes part of the conditioned space.
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Old 08-20-2012, 12:56 AM   #6
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Spray foam the interior of a exterior brick wall?


"If there is no vapor barrier in the wall do I spray the brick?"---- no, don't spray directly on the brick, as WoW said. Can you work some fanfold on the studs (to protect them from solar-driven moisture on the sunny-side), yet still leave an air channel for the brick? Then add the cavity XPS, canned foamed at all edges= air-tight. ADA the drywall.

Expect 10% less shingle life with a closed roof. http://www.buildingscience.com/docum...ion/#Cash_2005
If HVAC and ducts are in the attic, closed roof is good....if not, leave it vented.

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Old 08-20-2012, 02:35 AM   #7
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Spray foam the interior of a exterior brick wall?


The ducts are in the attic but if I seal it the gas heat will not get enough combustion air. I cant afford a ac overhaul atm. The roof is 7 years old . What type if canned foam should I use to air.seal the xps?
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Old 08-20-2012, 08:13 AM   #8
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Spray foam the interior of a exterior brick wall?


Very unlikely the sealed attic will starve the unit for combustion air but if you are concerned, test the draft on it.

A closed cell can foam is a good idea. I like the window and door specific stuff as it lays down a more representative bead and does not have any pull back issues.
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Old 08-20-2012, 12:58 PM   #9
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Spray foam the interior of a exterior brick wall?


I calL a sf contractor today and he recomended going to unvented route by spraying the brick,sealing the soffet and ridge cap. With 3in. 3lbs closed cell on walls and 5 in. on the roof. All for 8k. Does this sound right.
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Old 08-20-2012, 04:57 PM   #10
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Spray foam the interior of a exterior brick wall?


Quote:
Originally Posted by Convict3 View Post
I calL a sf contractor today and he recomended going to unvented route by spraying the brick,sealing the soffet and ridge cap. With 3in. 3lbs closed cell on walls and 5 in. on the roof. All for 8k. Does this sound right.
That doesn't sound like a bad price, what is the "R" he's telling you you will achieve with that? Foam from different manufacturers has different "R" values.
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Old 08-20-2012, 05:21 PM   #11
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Spray foam the interior of a exterior brick wall?


Where is the home?

That will dictate what is code compliant on the roof.
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Old 08-20-2012, 09:14 PM   #12
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Spray foam the interior of a exterior brick wall?


They are claiming r7 per inch bayseal brand closed cell
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Old 08-20-2012, 09:16 PM   #13
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Spray foam the interior of a exterior brick wall?


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Where is the home?

That will dictate what is code compliant on the roof.


South texas
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Old 08-21-2012, 08:01 AM   #14
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Spray foam the interior of a exterior brick wall?


Claimed R-Values are different than realized in most cases.

I would count on R-6 per inch and that is a more reasonable expectation.

R-30 should be fine at that point but where is Gary GBR when you need him...

http://publicecodes.cyberregs.com/ic..._11_sec002.htm

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