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Old 02-02-2012, 09:12 AM   #1
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Bathroom insulation question


I am going to tile the walls in the tub area, I haven't opened the walls yet to see what is there.

I plan to use cenement board on the walls with a vapor barrier. My concern is I don't want to remove the tub and that will pose a problem with completely sealing the vapor barrier.

The house is bricked and only one wall in the tub area faces an exterior wall. If I took spray foam insulation and sealed and openings and placed insulation bats in the wall cavity with a vapor barrier taping the seams as far down as I can do you think this would minimize air flow into the wall cavity?

Is unfaced insulation OK?

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Old 02-02-2012, 11:29 AM   #2
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Vapor barrier in NC or are you referring to just behind the tiled areas?

No vapor barrier requirement in NC.

Just seal the holes in the envelope with the foam where you can reach and insulate the exterior wall with fiberglass or other unfaced product.

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Old 02-02-2012, 11:44 AM   #3
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Bathroom insulation question


I am in the south central part of NC, I thought a vapor barrier was required to keep from getting moisture in that cavity. Thanks for the reply.

In surfing the net I have found some contradicting info on a number of topics from a number of DIY sites it boggles the mind. I am not insinuating that you are giving bum info.
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Old 02-03-2012, 10:31 AM   #4
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No vapor barrier requirements for NC. It is a blended climate and you don't require vapor barriers (depending on the insulation layer and exteriors) until North of Maryland on the East Coast.

Most important details in any wall assembly are to make sure they are air tight.

If you are worried about diffusion, you could install a Vapor barrier behind the shower walls but that would also be accomplished by any number of the better water proofing systems out there (Schluter Kerdi, etc).

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Old 02-03-2012, 01:27 PM   #5
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Apparently there is vapor barrier for the house, and vapor barrier/waterproofing/water barrier for a wet area or shower. Not necessarily the same thing.
It sounds like you're trying to tie them both together.
This may be more of a tiling question than an insulation question.
You might get more/other replies in the tiling forum.
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Old 02-03-2012, 01:52 PM   #6
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Quote:
Originally Posted by Windows on Wash View Post
Vapor barrier in NC or are you referring to just behind the tiled areas?

No vapor barrier requirement in NC.

Just seal the holes in the envelope with the foam where you can reach and insulate the exterior wall with fiberglass or other unfaced product.
I am not saying that you are wrong I am just curious how you know that about NC?
I did a little research and it looks like NC is now on the 2012 NC code, based on the 2009 IRC (might be wrong about that), I can't find any info on the vapor barrier requirements though.
All I can find are the ASTM 1288 requirement and the ICC # and it does not say anything about vapor barrier either.

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Old 02-04-2012, 10:59 AM   #7
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Quote:
Originally Posted by AndyGump View Post
I am not saying that you are wrong I am just curious how you know that about NC?
I did a little research and it looks like NC is now on the 2012 NC code, based on the 2009 IRC (might be wrong about that), I can't find any info on the vapor barrier requirements though.
All I can find are the ASTM 1288 requirement and the ICC # and it does not say anything about vapor barrier either.

Andy.
Where is GBR when you need him...

NC is either in climate zone 3 or 4 (tiny part 5) and may actually fall, depending on where the post is, below the hot humid line making the cool side the interior wall.

The issue with vapor barriers has much to do with the interpretation of what a vapor barrier is. This is why most people have converted to referring to vapor barriers as more properly vapor retarders and in doing such, different classes of vapor retarders.

http://www.buildingscience.com/docum...commendations/

Why you say vapor barrier, most folks think straight away of a warm side poly. If the poster did that in this case, they could very easily ruin the interior wall by creating a moisture trap if their home has and exterior foam sheathing or another vapor impermeable sheathing or layer.

The poster in this case will want to make sure their is certainly vapor diffusion control across the plane of the shower and that may be supplied by whatever membrane he/she might be using (i.e. Kerdi membrane or similar moisture management system for the shower). If they are just using a concrete board, an additional vapor control layer behind the shower and around where the steam will be settling on the drywall may be recommended.

The poster can also use a vapor barrier paint on the walls to limit the amount of diffused moisture through the walls.

Air loss will always carry much, much more water than diffusion which is why I recommended that the air barrier details be precise.

Climate zones 3 and 4 do not require any additional vapor control beyond a class II vapor retarder and usually a class III is acceptable if the cladding is not air tight (i.e. vinyl siding).

Whatever the cladding is, a true vapor barrier as most people think if it (i.e. poly plastic = Vapor retarder class I) is not required.

http://www.afhh.org/pol/pol_housing_codes_dry.htm

Excerpt from above article:

IRC 322.1: Moisture Vapor Retarders/Moisture Control. In all framed walls, floors, roofs, and ceilings making up the building thermal envelope, a vapor retarder must be installed on the warm-in-winter side of the insulation, unless the framed area is ventilated to allow moisture to escape. (Vapor retarders are designed to prevent the movement of moisture-laden air from the warm side of the wall to the cool side. In temperate climates, vapor retarders are placed on the interior (warm in winter) side of the wall cavity; in hot, humid climates, they are placed on the exterior (warm) side of the wall cavity. According to the Asthma Regional Coordinating Council of New England, walls should be designed to dry to both the interior and the exterior and basements should be designed to dry to the interior. Installing vapor barriers interferes with the ability of walls to dry in both directions, so their use should be limited to severely cold climates. Paper-faced cavity insulation should be used in place of plastic interior vapor barriers.)

Good Read here:

http://www.buildingscience.com/docum...doctypes/diges

From that article:

1. Zone 1, Zone 2, Zone 3 and Zone 4 (except Zone 4 Marine) do not require any class of vapor retarder on the interior surface of insulation in insulated wall and floor assemblies.

2. Zone 4 (marine) requires a Class II (or lower) vapor retarder on the interior surface of insulation in insulated wall and floor assemblies where the permeance of the exterior sheathing/cladding assembly is less than or equal to 1.0 perm and greater than 0.1 perm as tested by Test Method B (the “wet cup” method) of ASTM E-96).

3. Zone 4 (marine) requires a Class III (or lower) vapor retarder on the interior surface of insulation in insulated wall and floor assemblies where the permeance of the exterior sheathing is 0.1 perm or less as tested by Test Method B (the “wet cup” method) of ASTM E-96) and the interior surface of the exterior sheathing shall be maintained above the dew point temperature of the interior air. Under this design approach assume steady state heat transfer, interior air at a temperature of 70 degrees F (21 degrees C), at a relative humidity specified in Table 1 and exterior air at a temperature that is equal to the average outdoor temperature for the location during the coldest three months of the year (e.g. December, January and February).

Last edited by Windows on Wash; 02-04-2012 at 11:30 PM.
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Old 02-04-2012, 10:40 PM   #8
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Bathroom insulation question


WW, my ears are ringing.....LOL. Good explanation!

The only thing I might add is; with a brick exterior, unless the house is recently built or re-sided, there is probably only board sheathing (with tar paper) on the walls, an inch away from the brick. If a sunny-side wall, expect a huge moisture drive there because of the pressure/temperature differences; http://www.buildingscience.com/docum...n-brick-veneer

Similar read, with a link to EIFS in NC: http://www.greenbuildingadvisor.com/...moisture-walls

I would add rigid foam board between the studs, tight against the sheathing, caulking/canned foaming them in place. Add the f.g. and use G.P.'s DenShield or similar -- rather than a cement board that probably requires a poly v.b. behind it for the warranty. Dens. facing is waterproof so no water will leak through or wick: http://docs.google.com/viewer?a=v&q=...WlK87HmnplLw0w

Andy: Read and hit "next section" a few more times.... http://publicecodes.citation.com/ico...002_par024.htm Vented cladding = brick veneer in last section.

And, N.C., depends on City below the map: http://publicecodes.citation.com/ico...001_par009.htm
Now they list HDD to get even more techy (sp):http://publicecodes.citation.com/ico...001_par011.htm

Did you know: http://austin-green-builder.com/2012...e-irc-changes/

Oops, sorry, Joe T. I'm getting off subject.

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Old 02-04-2012, 11:31 PM   #9
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Gotta love the 2012 code.

More foam and government meddling in industry.

What isn't green about require oil based foams for the outside of the home...
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Old 02-05-2012, 02:12 PM   #10
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Bathroom insulation question


thanks everyone for the great response and information. I plan to read the links to more information.

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