>Do I need to install a vapor barrier over an exposed joist ceiling before spraying open cell foam insulation?
> I have constructed a small 16' x 21' living quarters in an open bay, in one corner of my metal (shop) building. The metal building has double bubble double faced radiant barrier in the roof (and walls). The living quarters has 2" x 4" stud wall construction, sheathed w/ 1/2" OSB, wrapped w/ 30# felt and sided w/ 3/4" western red cedar. The ceiling has exposed 3" x 8" reclaimed Douglas Fir beams with 3/8"- 4' x 8' sheet T1-11 rough siding, installed as the ceiling material. I have installed a 2" x 6" joist sub-floor over the ceiling, as I intend to use the overhead space for light/medium wt. storage. I intend to fill the sub-floor joist system w/ 0.5 lb. open cell urethane foam and then deck over with 1/2" plywood.
>The attic of the living quarters is closed on one end and the two sides. The remaining end has been left open for access to the overhead storage. The open end is still protected from the elements because the common roof line extends out an additional 21 ft. past the open end.
> QUESTION - Do I need to install a vapor barrier on the ceiling before spraying in the open cell urethane foam. I asked my local insulation contractor about this an he seemed to be unsure about this. He seemed to think that a vapor barrier wouldn't be needed in this situation. I want to make double sure whether a vapor barrier is needed in this construction. I am located in East, TX zip 75766, DOE climate zone 3. We have high humidity levels year round in my area. The humidity averages in the 80 - 90% range for the mornings and in the 60% for the afternoons. I do not want to create any moisture problems with the possibility of mildew/black mold in this ceiling/sub-floor system.
>I will heating/cooling this living space with a 12,000 Btu Mini-Split heat pump and an Aux. 10,000 Btu LP radiant space heater.
Any experienced advice about my project would be greatly appreciated. -:confused: Thanks, Perplexed in Texas