Is there such thing as insulating an unfinished attic too much, where it might change the lifespan of the roof shingles above, or cause deterioration. Is insulating between rafters “overkill” if the attic floor joists are already insulated with 9″inches thick combo of blown wool & roll Kraft faced battens? What is the rule of thumb for how close to run the faced roll fiberglass insulation to the ridge vent- to still permit air circulation/venting? How close to the soffit-plate can u run insulation? Is there a difference in the R-Value based on the installation method- stapling lips to face of wood framing versus stapling Kraft face lip to inner side of wood framing?
Thank You!!!!!!!!!!!!! Chipper [email protected] 10/12
Replies
You might do better on Fine Homebuildings forum or the http://www.diy.com
Knots is more furniture oriented.
If you wanted to add more insulation, place it on top of the insulation already on the attic's floor, placing it in the rafters would be a waste of time and materials.
Soffit and ridge vents need to be kept clear to vent moisture and hot air and in snow country to prevent the formation of ice dams. If you are having problems with any of these things consider installing larger vents in an end wall and possibly a fan. If you are having ice dam problems, the soffits need to be ventilated if they aren't already.
Kraft and foil facings, in theory, serve as vapor barriers and the foil reflects radiant energy but their performance is marginal at best. Tightly fitting unfaced fiberglass and using continuous poly plastic vapor barriers are far more effective. If you add more insulation to the attic floor it should be unfaced, since vapor barriers need to go against the inside surface of the wall, right behind the sheetrock.
If you provide specifics about why you want to add more insulation, and the climate where you live, I might be able to offer some advice tailored to your situation.
John W.
Home Depot has some stryafoam thingies that staple underneath the decking that forms a channel that will prevent the ceiling insulation from blocking the air flow from the soffit. They're cheap and highly recommended. I used them and put 10" fiberglass batts between the 8" ceiling joists. Running the thru-the-wall AC at it's lowest setting keep the rooms nice and cool.
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