steel roof trouble ?

[Hank]

I am building a cottage in north western PA. Although it is not finished, I have most of the ceiling insulated..R 19. I have the cottage heated only in the areas that the ceiling is insulated..pellet stove,space heaters 2. This past weekend we had a heavy frost and I noticed condesation dripping off the steel roof inside the cottage in the uninsulated rooms. Also dripping off the open porch which also is under the same roof. Will this problem go away when all insulation is finished? Have I missed something? What about the porch?

[Mr T]

You need to install a vapor barrier. This will happen any time warm air comes in contact with a cold surface (such as the side of a glass of ice water).

Once you get the place finished and sealed off from the outside you shouldnt have as bad of moisture problems. Chances are the humidity inside is high too.

Dont let this go too long as the moisture can run down the underside of your roof and cause water damage.

It wont happen under the porch if its not heated. If its the same roof slope it could be running down the underside of the roof from a (semi) heated area.

[Hank]

Thank you Mr. T for your prompt answer to my problem.

I have another question ...is the paper backing on the insulatoin an atiquite vapor barrier?

Is the roof sealed evan with a vented two foot soffit and ridge vent?

Sorry my knowledge In metal roofing as you can tell is very limited.


thanks again

Hank

[Mr T]

The paper backing is your vapor barrier. Install it so it faces the heated side of your place, Make sure to repair any tears or breaks in it. Dont leave it exposed as it is a fire hazard.

Do not double up the barrier either, otherwise you may trap moisture in your walls or other parts of the cottage.

Follow your manufacturers requirements for venting. Also check with local codes.

[Wgoodrich]

Most of this is not your tin roof but rather your insulation blanket and possibly your required ventilation design. I have not picked up yet if your rafters are also your ceiling or if you have an attic with both a rafter and ceiling as two sets of spanning lumber. You claim northern Penns. as your location. This northern area of your state requires as a minimum an R 49 for the ceiling and an R 21 for your walls for your insulation blanket.

What you discribe matches what would be expected. When a cold outside metal roof meets a warm inside contact you will have condensation. I also suspect that due to metal being a good convetion of heat that the tin warms up passing this warmth past your outside walls warming the tin roof part over your porch even when not heated in the porch area causing the condensation of that porch area also.

YOu claim you have installed R19 being an R value of 30 insuficient for your location to meet minimum accepted insulation blanket calling for R49.

It is true you either need to install paper backing on the warm side of your ceiling but never install 2 vapor barriers as advised against in previous replies.

Let us know if your have an attic and is so then if your installed soffit vents to allow vent air intake and roof vents at the peak of your roof to allow air vent outlet. If not and you are using a roof ceiliing combined then I suspect you will need to frame in a ceiling set up creating the attic to be able to meet your required R49 in your ceiling. Once you have meet the minimum insulation value required with proper vapor barrier and required properly installed venting your condensation problem will stop.

Hope this helps

Wg

[Hank]

Thanks Guys for all your help, I finished the insulating the cieling and taping any tears... does it still drip?... good question.. How can I tell? Thanks again.:banghead: