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Old 12-27-2008, 05:24 PM   #1
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vapour barrier on ceiling of bathroom?


Hi. my contractor has just finished our bathroom. He did not put a vapour barrier on the ceiling ovver the shower....he did use (however) blue board. He tiled over this blue board....
in the attic is blown insulation.
My question: did this ceiling need to have a vapour barrier? if so, now what? I cannot take down the tiles and add a vapour barrier...can I install a vapour barrier from the attic?
or will it be ok without a vapour barrier?
I was told that moisture will go up into attic and the air will be let out by the vents and the air coming in through the soffits...
any help? suggestions? thoughts? thanks

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Old 12-28-2008, 08:20 AM   #2
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vapour barrier on ceiling of bathroom?


Technically there should be a vapor barrier, but many things qualify as a vapor barrier, including paint. The vapor barrier is usually installed on top of the ceiling under the insulation. Tile would certainly qualify as a vapor barrier. But a drywall or plaster ceiling sealed with a primer and top paint coat also qualifies, most of the time.

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Old 12-28-2008, 11:27 AM   #3
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vapour barrier on ceiling of bathroom?


I've never seen any sort of specific vapor barrier used on ceilings (such as plastic). Make sure you have an adequate exhaust fan vented to the outside of the house, and as Just Bill stated, proper paint on the exposed drywall.......
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Old 12-28-2008, 11:33 AM   #4
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vapour barrier on ceiling of bathroom?


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Originally Posted by wilsonfrench View Post
Hi. my contractor has just finished our bathroom. He did not put a vapour barrier on the ceiling ovver the shower....he did use (however) blue board. He tiled over this blue board....
in the attic is blown insulation.
My question: did this ceiling need to have a vapour barrier? if so, now what? I cannot take down the tiles and add a vapour barrier...can I install a vapour barrier from the attic?
or will it be ok without a vapour barrier?
I was told that moisture will go up into attic and the air will be let out by the vents and the air coming in through the soffits...
any help? suggestions? thoughts? thanks
The point of applying a vapor barrier onto insulation (facing the warm area) is about condensation/humidity from temperature change (cold air meeting warm condiitoned air). In the situation/arrangment that you describe, there should be some sort of vapor barrier between the insulation and the warm area (bathroom). Dependent on regional building codes, this may be required because of the cold air meeting warm (heated) air (aka = dewpoint condensation).

As far as vapor coming thru the ceiling's painted drywall surface, this just isn't going to happen. If you have an exhaust vent, properly installed, and venting the moist bathroom air to the outside, and a proper coat of mildew resistant paint, these should suffice to protect the drywall from any moisture.

Now the thing I find hard to understand is, if the guy installed the blueboard and you have blown-in (loose) insulation, how did that stay up, when there was no sheetrock on the ceiling?

As far as mositure in the attic, you don't want that. But this is not going to take place from vapor traveling thru painted (protected) sheetrock. If you have an exhaust vent, make sure that is vented to the outside, and not into your attic.
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Old 12-28-2008, 11:42 AM   #5
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vapour barrier on ceiling of bathroom?


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Originally Posted by Just Bill View Post
Technically there should be a vapor barrier, but many things qualify as a vapor barrier, including paint. The vapor barrier is usually installed on top of the ceiling under the insulation. Tile would certainly qualify as a vapor barrier. But a drywall or plaster ceiling sealed with a primer and top paint coat also qualifies, most of the time.
Just to Clarify:

Tile in and of itself is not considered a vapor barrier, neither does a top coat of paint over drywall.

Are these areas able to resist moisture vapor? Yes, to a degree.

Are such surfaces categorized by building code, or industry standards as proper/recognized "vapor barriers" or "vapor retarders"? No, they are not.

http://en.wikipedia.org/wiki/Vapor_barrier
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Old 12-28-2008, 11:43 AM   #6
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vapour barrier on ceiling of bathroom?


More information on vapor barriers and regional needs: http://apps1.eere.energy.gov/consume.../mytopic=11810
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Old 01-04-2009, 11:29 PM   #7
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vapour barrier on ceiling of bathroom?


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Originally Posted by AtlanticWBConst. View Post
The point of applying a vapor barrier onto insulation (facing the warm area) is about condensation/humidity from temperature change (cold air meeting warm condiitoned air). In the situation/arrangment that you describe, there should be some sort of vapor barrier between the insulation and the warm area (bathroom). Dependent on regional building codes, this may be required because of the cold air meeting warm (heated) air (aka = dewpoint condensation).

As far as vapor coming thru the ceiling's painted drywall surface, this just isn't going to happen. If you have an exhaust vent, properly installed, and venting the moist bathroom air to the outside, and a proper coat of mildew resistant paint, these should suffice to protect the drywall from any moisture.

Now the thing I find hard to understand is, if the guy installed the blueboard and you have blown-in (loose) insulation, how did that stay up, when there was no sheetrock on the ceiling?

As far as mositure in the attic, you don't want that. But this is not going to take place from vapor traveling thru painted (protected) sheetrock. If you have an exhaust vent, make sure that is vented to the outside, and not into your attic.

Hi. I have installed the exhaust fan with a hose that expells the warm air through the a hole (which I cut) in the soffit....will this warm air be sucked back into the attic? ..thereby defeating the whole purpose of an exhaust fan?
I Have peforated soffits..thanks
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Old 01-04-2009, 11:30 PM   #8
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vapour barrier on ceiling of bathroom?


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Originally Posted by Just Bill View Post
Technically there should be a vapor barrier, but many things qualify as a vapor barrier, including paint. The vapor barrier is usually installed on top of the ceiling under the insulation. Tile would certainly qualify as a vapor barrier. But a drywall or plaster ceiling sealed with a primer and top paint coat also qualifies, most of the time.
...

not sure I understand...can I retro-install a VB now? in between the joist bays ?
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Old 01-04-2009, 11:35 PM   #9
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vapour barrier on ceiling of bathroom?


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Originally Posted by wilsonfrench View Post
Hi. my contractor has just finished our bathroom. He did not put a vapour barrier on the ceiling ovver the shower....he did use (however) blue board. He tiled over this blue board....
in the attic is blown insulation.
My question: did this ceiling need to have a vapour barrier? if so, now what? I cannot take down the tiles and add a vapour barrier...can I install a vapour barrier from the attic?
or will it be ok without a vapour barrier?
I was told that moisture will go up into attic and the air will be let out by the vents and the air coming in through the soffits...
any help? suggestions? thoughts? thanks
what is the proper way to exhaust a bathroom fan? (through the roof or through a soffit)?
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Old 01-05-2009, 06:04 AM   #10
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vapour barrier on ceiling of bathroom?


Vent your bath fan thru the roof.
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Old 01-05-2009, 06:10 AM   #11
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vapour barrier on ceiling of bathroom?


Quote:
Originally Posted by wilsonfrench View Post
Hi. I have installed the exhaust fan with a hose that expells the warm air through the a hole (which I cut) in the soffit....will this warm air be sucked back into the attic? ..thereby defeating the whole purpose of an exhaust fan?
I Have peforated soffits..thanks
No. You are moving that moisture laden exhaust-air through mechanical, "active", or forced means.

Soffit vents are static, or "passive" intake venting.

Additionally, that interior air that you are moving out, is generally warmer, and under most weather conditions: Warm air will rise, and move out & away from the underside of the soffits.
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Old 01-05-2009, 08:24 AM   #12
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vapour barrier on ceiling of bathroom?


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No. You are moving that moisture laden exhaust-air through mechanical, "active", or forced means.

Soffit vents are static, or "passive" intake venting.

Additionally, that interior air that you are moving out, is generally warmer, and under most weather conditions: Warm air will rise, and move out & away from the underside of the soffits.
...

so, I don't have anything to worry about? should I cover the soffits to the left and right of the exhaust vent (a pain-in-the-you-know-what) to get to because of its location (slope of roof and corner of house)...
I drew a photo to assist...even though you make clear sense...sounds like you have a lot of experience...however, could you explain how the soffits work? I thought that they suck up any air (warm or otherwise) around the soffits....
as such, I am not basically putting the warm air back into the attic? I know I have asked this two or three different ways...but I don't want to worry about it as I hate going up to the attic to potentially look for moisture. thanks (see photo)
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Old 01-05-2009, 06:08 PM   #13
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vapour barrier on ceiling of bathroom?


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Old 01-05-2009, 11:06 PM   #14
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vapour barrier on ceiling of bathroom?


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Originally Posted by AtlanticWBConst. View Post
The point of applying a vapor barrier onto insulation (facing the warm area) is about condensation/humidity from temperature change (cold air meeting warm condiitoned air). In the situation/arrangment that you describe, there should be some sort of vapor barrier between the insulation and the warm area (bathroom). Dependent on regional building codes, this may be required because of the cold air meeting warm (heated) air (aka = dewpoint condensation).

As far as vapor coming thru the ceiling's painted drywall surface, this just isn't going to happen. If you have an exhaust vent, properly installed, and venting the moist bathroom air to the outside, and a proper coat of mildew resistant paint, these should suffice to protect the drywall from any moisture.

Now the thing I find hard to understand is, if the guy installed the blueboard and you have blown-in (loose) insulation, how did that stay up, when there was no sheetrock on the ceiling?

As far as mositure in the attic, you don't want that. But this is not going to take place from vapor traveling thru painted (protected) sheetrock. If you have an exhaust vent, make sure that is vented to the outside, and not into your attic.
HI Atlantic, I am not sure of what the resolution should be...
do I install a VB on the warm side of the insulation (by going up into the joist bay)...
or do I not put any VB....
as for the sheetrock that was installed wihtout a VB...he took down the old drywall and the insulation fell down into the bathroom..it was not replaced...which is why I need it to get blown in now....
which brings me back to the original q..
VB in ceiling above shower? or no?
thanks!
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Old 01-06-2009, 05:31 AM   #15
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vapour barrier on ceiling of bathroom?


Quote:
Originally Posted by wilsonfrench View Post
HI Atlantic, I am not sure of what the resolution should be...
do I install a VB on the warm side of the insulation (by going up into the joist bay)...
or do I not put any VB....
as for the sheetrock that was installed wihtout a VB...he took down the old drywall and the insulation fell down into the bathroom..it was not replaced...which is why I need it to get blown in now....
which brings me back to the original q..
VB in ceiling above shower? or no?
thanks!
You should have a VB between the insulation and the warm side (bathroom) area.

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