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Old 11-17-2017, 03:12 PM   #16
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Re: Replace wall insulation?


I don't know why you're arguing against the use of a impermeable barriers even if they may not be essential to prevent rot.

They reduce air infiltration and movement through the walls, when done right, dramatically.

Sure they get some holes from nails, screws, etc, but the nail/screw heads stop most of the leakage anyhow. They can be sealed to electrical boxes and plumbing penetrations.

The connection to the framing can be done with acoustical sealant and the seams well tuck taped.

Relying on trim and electrical plates and some caulking/gaskets to stop leakage is crazy. It's not as effective, as houses shift, sealing materials age - new leaks get created.

No barrier is perfect, including the tyvec they put on the exterior.

Hence the need to have a good moisture permeable air barrier on the outside (which is also water proof and allows for drainage for what water gets in there) and a good, tight air barrier (whether it prevents vapour diffusion or not) on the inside.

I'm talking cold climates here.

I don't care about credentials; someone can be an scientist or engineer with a phd and still push for something that makes no sense.
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Old 11-17-2017, 03:25 PM   #17
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Re: Replace wall insulation?


@Bud9051 Some one figured out that old houses that had shiplap had air movement every 8" had much less rot than the houses closed up tight with plywood type products.
Plywood installed horizontal has 1/2 in gap between upper and lower sheets and closed cavities like under windows are drilled.
This much like air behind insulation in the attic.
@user_12345a They don't have acoustical sealant down there. they use something called quad for much of what we use acoustical for.
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Old 11-17-2017, 03:45 PM   #18
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Re: Replace wall insulation?


Really interesting topic that raises a question for the experts in this thread:

Since this is an old house, its unlikely the exterior sheathing is an air barrier, let alone a vapour barrier.

By putting up an interior vapour barrier, don't you now have to worry about solar vapour drive, as described here?

http://www.greenbuildingadvisor.com/...moisture-walls

That article makes me scared of using an interior vapour barrier - even in a cold climate.

If you've got well ventilated attic, and a well ventilated gap between your cladding and your sheathing, plus good interior air sealing (I know, its hard to get perfect without plastic), is winter condensation really that much of a worry?

My old home, for example, has soft clay brick - gets absolutely soaked in the summer rain and takes forever to dry.

That makes me more more worried about solar drive piling this rain-driven moisture on an interior vapour barrier in the summer, than I am about vapour from inside causing condensation issues in the winter.
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Old 11-17-2017, 04:25 PM   #19
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Re: Replace wall insulation?


My home has new vinyl siding on the upper floor that was installed this past year, but I was not the owner at that time so I cannot speak as to what is underneath. But I do not suspect that they covered with house wrap since that would be the right way and clearly nobody who lived here before me knew that concept.
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Old 11-17-2017, 04:33 PM   #20
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Re: Replace wall insulation?


Quote:
Originally Posted by jmetrail View Post
Really interesting topic that raises a question for the experts in this thread:

Since this is an old house, its unlikely the exterior sheathing is an air barrier, let alone a vapour barrier.

By putting up an interior vapour barrier, don't you now have to worry about solar vapour drive, as described here?

http://www.greenbuildingadvisor.com/...moisture-walls

That article makes me scared of using an interior vapour barrier - even in a cold climate.

If you've got well ventilated attic, and a well ventilated gap between your cladding and your sheathing, plus good interior air sealing (I know, its hard to get perfect without plastic), is winter condensation really that much of a worry?

My old home, for example, has soft clay brick - gets absolutely soaked in the summer rain and takes forever to dry.

That makes me more more worried about solar drive piling this rain-driven moisture on an interior vapour barrier in the summer, than I am about vapour from inside causing condensation issues in the winter.
I am not sure anything we have discussed here would apply to a solid brick house. I do know I know very little about brick houses.
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Old 11-17-2017, 04:37 PM   #21
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My home is brick veneer. Based on the article - it seems that solar vapour drive + interior vapour barrier can be a worry for any type of cladding (although a bigger concern for cladding that can hold rainwater). Of course, it's likely only a problem if you have air conditioning.
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Old 11-17-2017, 04:43 PM   #22
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Re: Replace wall insulation?


Quote:
Originally Posted by jmetrail View Post
My home is brick veneer. Based on the article - it seems that solar vapour drive + interior vapour barrier can be a worry for any type of cladding (although a bigger concern for cladding that can hold rainwater). Of course, it's likely only a problem if you have air conditioning.
You have about an inch behind the brick with house wrap or tar paper the track water down and you should have weep hole between some bricks around the bottom and maybe over windows.
So your house fits right in here.
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Old 11-17-2017, 04:47 PM   #23
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Re: Replace wall insulation?


Quote:
Since this is an old house, its unlikely the exterior sheathing is an air barrier, let alone a vapour barrier.

By putting up an interior vapour barrier, don't you now have to worry about solar vapour drive, as described here?
Interior vapour barrier is bad in hot humid climates.

Especially when the indoor temperature is below the outdoor dewpoint.

In cold climates that get some heat, design for cold still seems to take precedence.

If you use any non-permeable vapour barrier, you must to have drying potential on the other side even cold climates. You never, ever put a vapor barrier on both sides of the wall.

It's absolutely true that barriers, if done wrong or used in the wrong application, can create far more severe problems than they solve.


The air barriers like tyvec don't protect from diffusion, they're vapor permeable on purpose. They serve two functions -> air barrier while allowing moisture to get out of the wall and stopping water from getting in.

While a good point was made in the article, if you're in a really a really heating dominent climate with a little bit of a/c use, vapour barrier on the inside will be just fine.

The alternative is to cut 2 to 3" (R10 and R15 respectively) rigid foam and put in the stud cavities, seal edges with foam.

No moisture or air moving in or out, no condensation.
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Last edited by user_12345a; 11-17-2017 at 04:49 PM.
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Old 11-17-2017, 04:54 PM   #24
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Re: Replace wall insulation?


Good article on use of barriers in different climates -> https://www.energyvanguard.com/blog/...r-in-Your-Wall
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Old 11-17-2017, 05:09 PM   #25
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Re: Replace wall insulation?


Quote:
Originally Posted by user_12345a View Post
Interior vapour barrier is bad in hot humid climates.

Especially when the indoor temperature is below the outdoor dewpoint.

In cold climates that get some heat, design for cold still seems to take precedence.

If you use any non-permeable vapour barrier, you must to have drying potential on the other side even cold climates. You never, ever put a vapor barrier on both sides of the wall.

It's absolutely true that barriers, if done wrong or used in the wrong application, can create far more severe problems than they solve.


The air barriers like tyvec don't protect from diffusion, they're vapor permeable on purpose. They serve two functions -> air barrier while allowing moisture to get out of the wall and stopping water from getting in.

While a good point was made in the article, if you're in a really a really heating dominent climate with a little bit of a/c use, vapour barrier on the inside will be just fine.

The alternative is to cut 2 to 3" (R10 and R15 respectively) rigid foam and put in the stud cavities, seal edges with foam.

No moisture or air moving in or out, no condensation.
We use air conditioning a good chunk of the summer here. Plenty of days in the 80s and 90s in the summer with humidity.
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Old 11-17-2017, 08:43 PM   #26
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Re: Replace wall insulation?


Quote:
Originally Posted by 1995droptopz View Post
We use air conditioning a good chunk of the summer here. Plenty of days in the 80s and 90s in the summer with humidity.
Michigan has a heating dominant climate.

New houses are built with vapour barrier on the warm side up here; they don't rot. I'm just north of you in ontario.

You have to worry about interior vapor barriers being on the wrong side in areas where the outdoor dewpoint can be really high a lot of the time.


I don't think you get dewpoints in the 70s except for maybe a couple of brutal days.
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Last edited by user_12345a; 11-17-2017 at 08:47 PM.
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