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Old 12-19-2009, 03:04 PM   #1
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Sealing a brick on block envelope


My house is a 1957 ranch with a full walk-out basement. The (majority of) the outer walls are (from outside to in) brick, concrete block, wood furring strips, gypsum board. The attic is just a crawl space. We live near D.C. so we cool in the summer & heat & humidify in the winter.

When it's cold or windy outside, cold winds pour into the house on the main floor around the windows, outlets and baseboards. At least, they used to; I've used a heck of a lot of silicone caulk & the foam outlet covers and things are a bit better now. However, the wall itself still feels really cold to the touch - by hand on a cold day it seems to be the same temperature as the window itself (we've got good windows, but still!)

When I've searched for information on air infiltration I've found instructions for doing the inside sealing that I've done.
Doesn't it make sense to stop the air infiltration into the wall space?
Assuming that it does make sense - how do I do it? Where is this cold air coming from?
Also, I keep getting warnings from people (people who know nothing about this stuff, but like to give advice anyway) not to over-seal the house. Is this something I really have to be concerned about in my leaky house? And if it is, how could I tell when it crossed the line into over-sealed, aside from getting regular energy audits to test the air exchange rate?
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Old 12-19-2009, 04:33 PM   #2
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Sealing a brick on block envelope


no such thing as over sealing a house. All new building practices are moving towards this goal. BUT... sealing without controlling moisture is the problem. Also proper ventilation for the furnace, the water heater the dryer and bath fans become critical. Also outside air for a fireplace. Many older homes have not addressed these issues, thus when sealing well you create new problems. Water must be controlled. Keep it in the pipes and outside and away from the foundation. Even a small 1" square hole in drywall will deposit 30 pints of water inside the wall in a year. The old houses leaked. Thus 40% of your heat went out the building. On its way the heat dries the moisture in the walls. No mold. Fix only some sealing issues and do it wrong and now this moisture remains in the wall since you have sealed the wall surface.
The brick facing. This leaves an air space behind the brick. This cannot be sealed. This allows air flow to remove the moisture behind the porous brick facade. So here is an example of sealing improperly. A $100 laser thermostat is your best bet to check for air leaks and fix them. I used mine on a job today and found a slight difference on one awning window. Found it was not locking correctly and it registered 4 degrees less then the next window on the same wall.
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Old 12-19-2009, 08:03 PM   #3
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Sealing a brick on block envelope


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no such thing as over sealing a house
This is good to hear.

As for the proper ventilation that you mentioned - the dryer & water heater are OK. The water heater is gas but we have a carbon monoxide detector near it in case something ever goes wrong with the ventilation. The "furnace" is an electric heat pump, no problem there. 2 bathrooms have good fans, though we don't always use them - but that's changeable. The 3rd bath is a lost cause - poorly installed shower door was getting lots of water in the walls. I don't doubt that when I finally get up the nerve to look in that wall I'll find plenty of mold & have to re-do most of the bathroom. I'm not ready to do that yet, but I will add a fan when I do.
The fireplace does NOT get enough air, but we barely use it and could just crack a window. If we ever start using it regularly we can find a better solution.

Quote:
Even a small 1" square hole in drywall will deposit 30 pints of water inside the wall in a year.
You mean through to humidity & condensation?

Quote:
Fix only some sealing issues and do it wrong and now this moisture remains in the wall since you have sealed the wall surface.
OK, so how do I do it right/wrong? Is doing it wrong just sealing some spots but not all, so that moisture gets in but air flow is restricted?

Quote:
The brick facing. This leaves an air space behind the brick. This cannot be sealed.
I want to make sure I understand you correctly: Is there a space between the brick and the concrete block, or is the space between the block and the gypsum what you're referring to?
When you say "This cannot be sealed" do you mean don't use a brick sealant, or is there some other possible sealing of this space that I shouldn't do?

Thanks for the advice!
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Old 12-19-2009, 08:41 PM   #4
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Sealing a brick on block envelope


Quote:
You mean through to humidity & condensation?
Warm air on the inside will attempt to move into the wall to get to the outside cold air. So humid air inside enter the wall cavity where ever it can. This is why the code requires a vapor barrier on the warm side. But normally these are not sealed completely. Thus you get a problem with tight homes that now trap this moisture. If the seals are complete all is fine. In basements this is a problem because the colder underground wall allows the water to condense. This is why I recommend a sealed 2 thick foam insulation or spray foam on these areas. (below grade only) In above grade walls the wall needs to dry to the outside. The air vapor prevents humid air entering and the tyvek (house wrap) keeps water entering but allows the inside of the wall to still breath to the outside air.

Brick on wood will need this air space. If your brick is on concrete or block there will be no air space concern. If you do find any air leakage seal it.

The gas furnace and water heater and your fire place and the dryer and the baths are the main water producing sources in the home. In a tight home you will need to use a dehumidifier to keep the humdity low to avoid the issues mentioned above. This is one of the reasons some are suggesting not to make the house too tight.

With tight homes I control the air with an air exchanger and controlled circulation fans as well as humidifiers and dehumidifiers in the HVAC duct work.
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Old 12-20-2009, 05:56 AM   #5
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Sealing a brick on block envelope


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If your brick is on concrete or block there will be no air space concern. If you do find any air leakage seal it.
My walls are brick on block.
I think I know how to seal all of the leaks between the rooms and the interior of the walls (between the wall board and the block).
I am under the impression that there are also leaks between that interior wall space and the cold, outside air. Where would these outside to in-the-wall leaks be? Just around windows and door?
Are there other joints that might need sealing that I'm not thinking about? The brick-on-block itself can't be that porous, right?
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Old 12-20-2009, 06:27 AM   #6
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Sealing a brick on block envelope


This facade is porous and as such it should have a rain shield and house wrap to avoid the air and water infiltration
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Old 12-20-2009, 08:16 AM   #7
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Sealing a brick on block envelope


What is a rain shield?

You say I need house-wrap. Do you mean something like Tyvek? Outside the brick? Wouldn't that mean putting another layer of facade outside the Tyvek? Am I missing something?
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Old 12-20-2009, 08:22 AM   #8
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Sealing a brick on block envelope


Both of these materials are installed during construction. You can not retro-fit these. Tyvek is a house wrap. It is used to block wind driven moisture into the wall cavity while still allowing the moisture in the block to dry to the outside. But bricks are very porous and I install a rain shield also. This is a material with vertical channels that block all moisture trapped inside this wall and allow it to drain out the bottom of the wall cavity.
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Old 12-20-2009, 08:27 AM   #9
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Sealing a brick on block envelope


That's what I thought.
My house is all built - what can I do now to seal my walls? Cold air is somehow getting through or around the brick on block and chilling the small space between the block and the gypsum board. This makes the walls radiate cold. How can I fix it?
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Old 12-20-2009, 08:39 AM   #10
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Sealing a brick on block envelope


are your outside/exterior walls cinder block with a brick veneer? does the block and brick go to the roof framing?
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Old 12-20-2009, 08:49 AM   #11
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are your outside/exterior walls cinder block with a brick veneer?
Yes - brick, block, furring strips, gypsum - built in 1957 so no insulation, no moisture barriers
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Old 12-20-2009, 08:51 AM   #12
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Sealing a brick on block envelope


only way to fix this is to remove the drywall and fill the entire wall cavity with closed cell spray foam. You can do this one room and one wall at a time. Buy the DIY spray foam kits. And remember you get 1500 tax credit this year or next year.
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Old 12-20-2009, 09:00 AM   #13
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Sealing a brick on block envelope


the transfer of cold thru all that masonry is hard to stop and having furring strips is no insulation. About the best you can get without major investment is to use a good grade of sealant/caulk at all your windows and doors. Youcan also seal wall plates with gasket materials on drywall side. If you are on a crawl space insulation there at the perimeter is important.
I believe part of the problem with this type of construction with no insulation is you get a chimney effect thru the space between the cinderblock and brick and between the furring strips and block so any wallpenetrations is going to pull air into your living space.
Sealing wall penetrations is a first step
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Old 12-20-2009, 09:53 AM   #14
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Sealing a brick on block envelope


tpolk, just realized I hadn't answered your second question
Quote:
does the block and brick go to the roof framing?
Yes, all of the original above-grade walls are brick on block up to the roof.
To be clear: the furring strips are only every few feet, they are only there to hold the gypsum board. There is definitely a chimney effect going on between the gypsum board and the block.
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Old 12-20-2009, 10:01 AM   #15
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Sealing a brick on block envelope


Quote:
fill the entire wall cavity with closed cell spray foam.
Bob, I don't have studs holding up the wallboard, just 1/4 furring strips, so my wall cavity is only 1/4 deep. Are there any issues with using spray foam in such a small space? I know it rules out other forms of insulation.
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