Repair help for the do-it-yourselfer.
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Posts: 1
Joined: Wed Jan 21, 2009 9:28 pm

Wed Jan 21, 2009 10:09 pm

Hello, I looked through the posts but can't find a definate answer to this question and would appreciate some help.

I just remodeled (this summer) an older mobile home...
Sealed the roof outside so it has no leaks anywhere (tested during several inches of rain in Dec.)

I wasn't able to finish the inside before winter hit, but put plastic vapor barrier then insulation (R-19). but no actual ceiling. However my cat needed a place to stay for winter (can't stay where I am :cry: ) so I got the natural gas heat to work for her.

Within 2 days the condensation built up and starting dripping through the insulation..

So I put in 7/16" OSB for a temp ceiling throughout the entire home

That didn't help at all...

When the temp outside is below freezing no drips, but when it rises above freezing the water flows like somebody turned on a facuet.

What can I do to stop this? My kitty is getting wet :shock:

There are no actual roof vents.

Should I install a couple of vents or what?

Would a de-humidifier work?

The insulation is getting ruined and now so is the OSB

Please help

Thank You

Posts: 66
Joined: Sat Jan 05, 2008 2:16 pm

Thu Jan 22, 2009 9:13 am

Your problem (I think) is the plastic you used.
If you put the plastic behind the insulation, condensation is forming on the warm side.Typically, you install insulation and then plastic but if the plastic is not air tight you will still get condensation. You should have vents in the roof....this keeps the attic dry, allows the roof deck to freeze and prolongs the life of the shingles/roofing. The system works best with soffit or gable vents to let air in

User avatar
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Fri Jan 23, 2009 10:06 am

Vapor barriers should always be towards the inside of the house. IOW, attached behind your drywall (in your case OSB). Then insulation behind or above that.

Is the condensation forming on the bottom of the roof deck?

You definitely should ventilate your attic area. Moisture always needs an exist through your roof to keep it from collecting and causing problems like you describe. Unless of course your attic space becomes completely sealed and conditioned like the inside of the home which is not the case in 99% of houses.

Is your furnace vented properly? I know that water vapor is a byproduct of propane heating which can add lots of moisture to a house. Not sure about natural gas though.