Insulation, Radiant and Vapor Barriers - Wisconsin Garage Vapor Barrier
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zugdud
12-02-04, 03:28 PM
Howdy folks, I just got started insulating my detached garage. The garage is 2x4 wall construction with 1/2" thick exterior wall boards (not sure of the exact term for them) And a 2x6 celling so I went with R-13 Kraft faced batts for the walls and R-19 Kraft faced batts for the celling. My heat source is a propane bottle heater am Im hoping to keep the garage at around 50 degrees when its freezing outside. Im using unpainted 1/8" plywood as my interior wall
Anyway I talked to a few guys and got mixed results about vapor barriers. Most of them say, the kraft face is enough of a vapier barrier for the Wisconsin climate but some have suggested that I also put a clear plastic vapor barrier up as well (directly over the kraft barrier). Seeing as how it's not that hard to do, should I just go ahead and do it or would it make no difference?
Thankyou
Anyway I talked to a few guys and got mixed results about vapor barriers. Most of them say, the kraft face is enough of a vapier barrier for the Wisconsin climate but some have suggested that I also put a clear plastic vapor barrier up as well (directly over the kraft barrier). Seeing as how it's not that hard to do, should I just go ahead and do it or would it make no difference?
Thankyou
resercon
12-02-04, 08:03 PM
Because it is a garage and you are using a propane heater, I would not recommend using the plastic sheeting as a vapor barrier. And I would recommend against using plywood.
Plastic sheeting used as a vapor barrier is allowable directly over Kraft faced insulation. It would not be allowable on the other side of the Kraft faced insulation. The plastic is used primarily as an Air Barrier when installed directly over faced insulation. The reason why I do not recommend its use is because of the variety chemicals found in a typical garage. In other words, I would prefer you have more air exchange than less and an Air Barrier would provide less.
The reason why I recommend against the use of the plywood is that it would be adding fuel to a fire if one should happen. In other words, with sheet rock, you would have a better chance in salvaging something inside the garage if a fire should break out and you will have little or none if it happened and you had plywood walls and ceiling.
Plastic sheeting used as a vapor barrier is allowable directly over Kraft faced insulation. It would not be allowable on the other side of the Kraft faced insulation. The plastic is used primarily as an Air Barrier when installed directly over faced insulation. The reason why I do not recommend its use is because of the variety chemicals found in a typical garage. In other words, I would prefer you have more air exchange than less and an Air Barrier would provide less.
The reason why I recommend against the use of the plywood is that it would be adding fuel to a fire if one should happen. In other words, with sheet rock, you would have a better chance in salvaging something inside the garage if a fire should break out and you will have little or none if it happened and you had plywood walls and ceiling.