vapor barrier question

2 years ago, I built a 18x22 workshop in my back yard in Colorado. It basically goes unheated during the winter, except when I working in it and I use a space heater. When I insulated the attic area, I placed R-19 bats between the rafters directly on top of the ceiling boards. My question is in regards to a vapor barrier. I don't know if its necessary in this situation. If I remember correctly, the bats had a paper backing and I did put that side down onto the ceiling boards. If a vapor barrier is needed, what would be the best way to resolve this?
Rob
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Building codes say that 6 mil PE should be stapled to the joists before ceiling material is installed. Since that may not be possible, coating the ceiling with an oil based primer and paint might work best plus whatever caulking is needed. It could slow down the vapor transmission enough to avoid problems in the attic/roof area like condensation fueled mold development. Roof and soffit vents are desirable, if possible. The simple paint barrier might be all you need for the present.
Joe
Joe
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Joe, Thanks for the advice. It would be a pain to staple PE to the joist now. The ceiling and walls are OSB with 2" slats covering the joints. I put three coats of latex paint on all surface. I may go back and caulk everything. The attic has dormer vents on both ends for cross-ventilation.
Thanks again.
Rob
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I would question the value of that procedure in this situation. The point of that placement is to assure that moisture inside condenses below the barrier, to keep the insulation dry. However:
-- in rlz's situation, occasional use as a workshop, I doubt there's going to be much moisture inside to condense, unless he uses a humidifier, or if his space heater is an unvented gas one.
-- any condensation in this location would get into the ceiling material. Obviously you'd much rather have it in the ceiling than in the insulation, but it's still a consideration.
Rob/rlz didn't mention whether he A/C-s the workshop in the summer. Even Colorado can get damp in the summer, and A/C would cause outside humidity to condense on top of the barrier--where the insulation is.
So I would say examine the attic under worst conditions, and if the insulation feels damp, consider an additional barrier. Worst conditions would be:
-- Cold outside with high relative humidity, using the workshop for a long period of time with several people, a humidifier, or an unvented gas heater inside.
-- Hot and moist outside, running A/C inside.
Edward
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