Wet roof!!!

[basslips]

Just had a new pole barn built that I plan on living in for a couple of years till we build a house. Standard pole barn with all metal roof and metal siding. They put a vapor barrier down before laying the roofing. I then put up R-19 insulation between the purlins and covered the area in between the trusses with white plastic sheeting to kinda seal off the insulation and provide more reflection for lighting. The trusses are doubled up and are 12' oc. In between the sandwiched truss you can see the kraft backed insulation.

The last few mornings is been getting pretty cool, probably low 40's high 30's and getting fairly warm during the day, mid 60's bright and sunny. I first noticed the windows inside getting lots of condensation. Yesterday I noticed some dark spots in a few places. Dug a ladder out and sure enough it was very wet. Stuck my hand up between the insulation and the bottom of the vapor barrier and was very wet and extremely warm. Checked a few other areas and they were damp also.

Looked again about 9pm and the paper had dried out but behind was still damp. Checked early this am and still dry but even wetter than yesterday. Last night I removed a section of the white sheeting and then in another section did that plus pull a couple of batt's of insulation out to see what happens today.

I talked to the builder about my plan to do this and he said it would be fine as they put the vapor barrier down.

Another friend said it should be fine when I get my pellet stove hooked up and heat the building. But I don't plan on running the durned thing 24/7 all year round!

What are my options? Pull everything out and spray foam? Just remove white plastic sheeting? Cut in some vents in the roof? Put 2 gable vents in up high and get some air circulation just under the insulation?

Could this be caused by my concrete slab putting off moisture as it cures? It's about 6-7 weeks old. Would a sealer help with this if that's the case?

Thanks,
Dave

 

[trbomax]

It sounds like the steel is sweating but not knowing what you used for a vapor barrier makes it hard to diagnose. Normally, a total vapor barrier is not used between the steel and the purlins,but rather a foam sheet that is 3/8" to as much as 1" thick. The vapor barrier,if used,would go on the inside,over any insulation.I personally would never use FG against a roof,regardless of any other circumstances, without an airspace between it and the roof of at least 2".This would be in conjunction with a fully vented eve/soffit and ridge.
,which you did not specify in your post.

 

[henrysgarage]

Vapor barrier should not be on the cold side of the insulation, it stops the humidity from escaping above the insulation. I would think that the moisture is collecting on the underside of the vapor barrier and dripping down. On my garage the building inspector said I need to put the tarpaper only where the existing garage roof has plywood sheeting before I put on the steel roof. The new extension does not need to have anything below the steel roof. You need a lot of ventilation in the attic area. There should be a couple of inches of air space above the insulation. On a new build it sometimes takes up to a couple of years for the moisture to normalize. You need some heat in the building to try and dry it out. Also the floor adds some moisture while drying.

 

[basslips]

So I just checked and the moisture is definately better than yesterday but it is also colder with a good wind. The temps between the insulation and roof metal is alot cooler than yesterday. Still some moisture in a few places, none in a few that did yesterday. When I put heat in the shop will it get worse as there will be warmer air up high or will it get better?

 

[basslips]

Also thought worst case scenario short of pulling it all out and spraying in closed cell foam would be to just build a drop ceiling and the vent the new attic space. Being it's only a 12' eve building it will kill my height inside though.

 

[stealthbob]

Vapor barrier should not be on the cold side of the insulation, it stops the humidity from escaping above the insulation.

This is a very accurate statement...vapour barrier only on heated (inside) side, anything on the other side has to be able to breathe.

 

[basslips]

So in theory I could pull the roof sheets off and pull out the vapor barrier that the contractor put in and then lay metal back down and be ok?

 

[trbomax]

No,the metal will still sweat and drip on your FG. You can pull the steel and lay down a foam insulation house wrap,this will prevent the sweating and allow moisture to escape. You still need air space and venting above the FG.