Insulation, Radiant and Vapor Barriers - damp drywall
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boonie
01-02-09, 04:05 PM
Hi everyone. I hope I have this in the right forum. I have a detachted garage that the walls are insulated with no drywall at the present time. The ceiling is drywalled with plastic behind it with no insulation yet. My problem is, about a week ago I noticed the drywall along the walls looked damp. It was after a cold snap and got up to about 38 degrees in the following days. I went up in the attic and noticed moisture between the plastic and drywall. I understand it is because it's not insulated. But will it eventually dry out or will I need to take some kind of action. I'm just concerned about the ceiling taking on permanent damage. Then do I wait till spring with consistent warm temps to insulate? Thanks much, Jason,WI.
Rivethead
01-04-09, 01:10 PM
Opinions will vary on the need for a vapor barrier on the ceiling. My personal vote is no and if you do go that route use kraft faced insulation and then blow additional insulation on top if you want. The kraft paper serves as a barrier but it will allow moisture to escape.
Presuming you have the proper vents in place already and the vent chutes are in place for the insulation I'd go ahead an do it. The moisture isn't going anywhere except back through the drywall as it dries. Once it completely dries consider painting it with two coats of vapor barrier primer and then a couple coats of latex paint. This should prevent most of the moisture from building up behind the drywall again.
Good luck....
Presuming you have the proper vents in place already and the vent chutes are in place for the insulation I'd go ahead an do it. The moisture isn't going anywhere except back through the drywall as it dries. Once it completely dries consider painting it with two coats of vapor barrier primer and then a couple coats of latex paint. This should prevent most of the moisture from building up behind the drywall again.
Good luck....
Bud9051
01-04-09, 02:19 PM
Hi Jason, and welcome to the board. Is your garage heated and are you parking cars in there now with snow on them?
Bud
Bud
airman.1994
01-04-09, 06:21 PM
[QUOTE=Rivethead;1495165]Opinions will vary on the need for a vapor barrier on the ceiling. My personal vote is no and if you do go that route use kraft faced insulation and then blow additional insulation on top if you want. The kraft paper serves as a barrier but it will allow moisture to escape.
Kraft paper is not a VB. It does not have a high enough perm ratting.
Kraft paper is not a VB. It does not have a high enough perm ratting.
Rivethead
01-04-09, 07:51 PM
[quote Kraft paper is not a VB. It does not have a high enough perm ratting.[/quote]
Agreed - the correct term would have been Vapor Retarder.
Agreed - the correct term would have been Vapor Retarder.
boonie
01-05-09, 02:12 PM
Yes, I do park my vehicles in the garage now. I currently do not heat it because I have no insulation in the ceiling. From time to time I would run my kerosene heater when I was tinkering in there, but ever since I noticed the moisture I quit with that. As far as the vapor barrier it's a little late for that, I put plastic up before I drywalled the ceiling.:o That way I planned on just blowing the insulation on top of that. I can't exactly put batts up because I have a 12' wide floor running end to end. With that in mind, should I wait til spring to insulate or will it not harm to do it now? Will the moisture between the plastic dry out and the moisture in the drywall dry out as well? Thanks for the replies, Jason, WI.
boonie
01-10-09, 12:46 PM
Does anyone else have an opinion?
21boat
01-10-09, 06:10 PM
Jason wi Your post was a little confusing but heres the quick skinny from a old builder.
A vapor barrier MUST be on the warm side of the wall period. If there is a side wall in the garage and its insulated the vapor barrier is ti be on the heated house side wall. For a heated space above a garage the vapor barrier MUST be up against the plywood of the sub floor and not on the bottom of the floor joist in the garage. I do this for a living and still can't believe how insul is insulted wrongly time after time for some builders and usually most home owners.
So thats the skinny oh by the way if insulation gets damp by 5% moisture it looses 95% on its "R" value
Just to get everybody on board here. Kraft faced insul is sold in cetian parts of the U.S. It in its region considered a vapor barrier and the permeable amount for the "barrier" is accepted as such. Now in northern parts of the states and Canada not only can you not use kraft faced insul, the big box stores don't even really sell it becauseits 6ml poly and tuck tape seams.
The reason other Geo has unfaced and faced is because if you ADD more insul on what you have now you can't do a double vapor barrier and trap the air flow in the middle of the thermal transition
This is not an opinion as to put up or not put up a vapor barrier. Spray foam is the only insul besides polystyrene foam board that a vapor barrier is NOT needed
A vapor barrier MUST be on the warm side of the wall period. If there is a side wall in the garage and its insulated the vapor barrier is ti be on the heated house side wall. For a heated space above a garage the vapor barrier MUST be up against the plywood of the sub floor and not on the bottom of the floor joist in the garage. I do this for a living and still can't believe how insul is insulted wrongly time after time for some builders and usually most home owners.
So thats the skinny oh by the way if insulation gets damp by 5% moisture it looses 95% on its "R" value
Just to get everybody on board here. Kraft faced insul is sold in cetian parts of the U.S. It in its region considered a vapor barrier and the permeable amount for the "barrier" is accepted as such. Now in northern parts of the states and Canada not only can you not use kraft faced insul, the big box stores don't even really sell it becauseits 6ml poly and tuck tape seams.
The reason other Geo has unfaced and faced is because if you ADD more insul on what you have now you can't do a double vapor barrier and trap the air flow in the middle of the thermal transition
This is not an opinion as to put up or not put up a vapor barrier. Spray foam is the only insul besides polystyrene foam board that a vapor barrier is NOT needed