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

 

[blkhonda1991]

the vapor barrier should be on the warm side...it seems that you have vapor barrier over the trusses and insulations behind the vapor barrier? im not sure im really following how your roof is constructed is it:

metal roof
purlins
vapor barrier
truss
insulation?

 

[basslips]

Metal roof
vapor barrier
purlins
trusses
insulation between purlins up against vapor barrier

 

[rodnok1]

You have vapor barriers on both sides of insulation, like was said it should only be on heated side. If the insulation already had kraft paper on it you're doubling the condensation up, no place for it to go.

 

[basslips]

****...well I guess I could pull the insulation out and see how the pellet stove keeps up in the next couple of months.

 

[rickycobra]

You best bet is to do preventative maintenance and get rid of the damp areas and stop water from coming through.

 

[scott37300]

I don't have any experience with metal roofs but agree with the others about the double vapor barrier.

I believe if you would keep the insulation in the trusses and not the purlins and vent The purlin space to the outside you would be ok. In houses with vaulted ceilings where the insulation goes tight to the roof sheathing you use foam spacer vents to allow air flow above the insulation. Not sure if what I said is an option for you but might be something to look into.

 

[blue dog]

I don't have any experience with metal roofs but agree with the others about the double vapor barrier.

I believe if you would keep the insulation in the trusses and not the purlins and vent The purlin space to the outside you would be ok. In houses with vaulted ceilings where the insulation goes tight to the roof sheathing you use foam spacer vents to allow air flow above the insulation. Not sure if what I said is an option for you but might be something to look into.

The way Scott has described is the way we do it, with the exception of providing ventilation at the ridge and at the perimeter. What you are getting is condensation. As stated before the vapor barrier should be on the warm side.

 

[scott37300]

The way Scott has described is the way we do it, with the exception of providing ventilation at the ridge and at the perimeter. What you are getting is condensation. As stated before the vapor barrier should be on the warm side.

Blue dog, out of curiosity, you say that you don't vent to the outside? I'm only familiar with shingled roofs but from what I know you always want the "attic space" vented from the soffit to the ridge. Even when The insulation is in the rafters and you use the foam baffles you still want that area in the baffles to be vented right? So why wouldn't you do that in metal roofs also? Also in the OP's situation the builder put a vapor barrier on the cold side and he is putting another on the warm side. So if he doesn't vent at all and just leaves a gap wouldn't that still create moisture issues?

Just trying to understand this and learn a little from a contractor!

 

[blue dog]

Blue dog, out of curiosity, you say that you don't vent to the outside? I'm only familiar with shingled roofs but from what I know you always want the "attic space" vented from the soffit to the ridge. Even when The insulation is in the rafters and you use the foam baffles you still want that area in the baffles to be vented right? So why wouldn't you do that in metal roofs also? Also in the OP's situation the builder put a vapor barrier on the cold side and he is putting another on the warm side. So if he doesn't vent at all and just leaves a gap wouldn't that still create moisture issues?

Just trying to understand this and learn a little from a contractor!

It is important to create a cavity that air can flow from top to bottom, meaning at the roof and wall connection in every joist bay as well as at the ridge for the air to escape. The temp difference between inside and outside is what causes the condensation. With out this, even with the vapor barrier does not mean that condensation is being generated
As long as the roof is done properly I E waterproofed, and there is a air gap for each bay to vent above the insulation, condensation will be eliminated.
Now, i am in the west where it does not get as cold as where a lot of you guys are, this is the method we have been using without fail. When we did vaulted ceiling without venting, we had moisture issues, we do not use moisture barrier where i build, the closest thing we do is tyvek, under siding.
Have you ever slept in a truck with a camper shell in cold weather, there is all ways condensation inside the shell, there is no cross ventilation, this is what causes the condensation. Now, it the shell was vented top and bottom, this would be eliminated.
Doing this as i have explained, does not mean that you lose the r value of the insulation in the building.
Moisture is a killer, it will cause dry rot and mold.
Make note that it is just as important to supply the air as it is to let it vent.
In standard construction using a cut and stack joist method on say a 5/12 pitch, joists 16" on center, normally i will supply 2 2" holes at the rafter blocks that lead outside, with screen on them so bugs and such can not get and at the ridge i will use a ridge cap in the roofing with 2 2" holes drilled in each block between rafters, then drill holes in the sheeting as to let the air out the vented ridge cap shingles.
I hope this makes since, i am confused now.
Bottom line is air flow, it is important and will eliminate condensation, That is what is being generated here.

 

[basslips]

Thanks for all the input guys. So I just got down off the ladder and checked the roof out again. The first place I checked was the roof where I pulled a couple of batts down so just the original vapor barrier is exposed. Covered with condensation. I thought that eliminating the "double" vapor barrier I had created might help with this.

It seems as of right now there is no easy fix for this. I can either pull off all the tin and put in air baffles that will raise the roof thus making all the eve trim and what not, not line up, or just build a drop down ceiling and pull all the insulation down and put it there. While that will take more time, it won't cost all that much more. I can then properly vent the eve's and put some gable vents in to vent the new attic space. Only bummer is losing all the loft space above the rooms I built as the building is only 11' from floor to bottom of truss.

Maybe i'll take some pictures and what I have later this morning so you guys have a better visual.

Thanks again,
Dave

 

[blue dog]

Basslips, if you can fur down the insulation from the roof sheeting by 2"s from the wall to the ridge and vent top and bottom with some holes, your problem should be solved. The insulation will compress. Nail some 2x2's in the rafter bays below the sheeting. Do this from inside. What you were talking about is a lot more work.
From a engineering stand point, if your roof is waterproofed properly and you have cross ventilation in each rafter bay, realistically, vapor barrier is only a extra touch of protection. I will probably catch hell for saying that, but o well.
just remember moisture is bad for all lumber and insulation. If you have some mold in your investigation, spray down the lumber with bleach And let it dry before covering it back up, and remove and replace the wet insulation so as to not promote a good habitat for mold.
Good luck and what part of the country are you in?

 

[basslips]

Thanks for the tips. I'm in western Oregon so we get lots of rain....