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DEAR POLE BARN GURU: Finishing & insulating inside pole barn that was here when purchased last year. What are your thoughts on vapor barriers for ceiling between the metal and insulation?
Also in quandary over no over hangs for soffit vents it’s a Mo**on with the gable ends venting where trim meets the ribbed siding, snow blows inside currently and not sure if after I have it closed in it will still do so and get insulation wet (fiberglass). Thanks BLOWING IN, IN OHIO
DEAR BLOWING: It is essential to have a vapor barrier between the roof steel and any conditioned area below. In the event there is not a vapor barrier between the roof purlins and the roof steel, there are some options. The best choice, is also the most work. Remove the roof steel, install a reflective insulation on top of the purlins and reinstall the roof steel, using larger diameter, longer screws than what originally held it in place. Spray foam insulation could be placed on the underside of the roof steel (may be cost prohibitive), or reflective insulation could be installed under the roof purlins, as long as all of the seams are tightly sealed.
Assuming you are placing the fiberglass insulation at ceiling level, there should not be a vapor barrier below it. You want any warm moist air from inside the building to be able to rise into the dead attic space, which must be adequately vented. Venting can be accomplished by a combination of sidewall eave vents and a vented ridge, or by gable endwall vents.
If snow is coming in under the gable end/rake trim, the screws can be removed from the gable face of the trim, expanding closures can be placed along the edge of where the trim lies, and then reinstall the trim using metal-to-metal stitch screws. The expanding closures should be placed so the lower edge of the closure is just covered by the trim.
In any case, you want to be certain any fiberglass insulation will not get damp, as it will lose its effectiveness, as well as possibly contributing to decay of any wood members it is in contact with.