Chris writes yet again from State College, Pennsylvania: “One last question – it is possible to use faced insulation with existing insulation. If so how – face up or down?
Perhaps. When insulating on top of existing insulation we recommend the use of unfaced insulation so no vapor retarder will be on top of the original insulation. This will avoid creating a situation where moisture is trapped between two vapor retarders. Having said that I will also admit that a vapor retarder can be placed up to one-third of the total thermal resistance in the assembly starting from the warm side. If the insulation you are adding has at least twice the R-value of the insulation in place, then it should work. Unless you live in a very humid area and your local building code has a special requirement, the vapor retarder should always be on the warm-in-winter side.
Related Questions
- Ed writes from Pittsburgh, Pennsylvania: "My attic is 2x4 trusses with R30 insulation. Any suggestions on how to install 7/16 osb sheets which will serve as flooring for some needed storage?
- Chris writes yet again from State College, Pennsylvania: "One last question - it is possible to use faced insulation with existing insulation. If so how - face up or down?
- Sheila writes from Shawnee, Kansas: "My attic already has some shredded paper insulation. I bought faced insulation; do I install paper face down or up?
