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attic insulation

I have approx 10 to 12 inches of blown in insulation in attic , any problems adding unfaced r-30 batts on top of it ??

Re: attic insulation

Why would you do that,are you getting the batts for free. You would be cheaper getting a company to do it or rent the blower and do it yourself.......

Re: attic insulation

You can install your own batts between joists; choose batts whose thickness will make them flush with the top of the joists. If the batts protrude above the joists and there are gaps between the joists, the batts aren't providing much insulation value above that level. You can install a second layer of batts over top of batt insulation in the joists; layer it crosswise to the joists and don't leave any gaps between the batts. Never lay batt insulation over top of blown insulation


Re: attic insulation

I'll have to disagree with saying " Never lay batt insulation over top of blown insulation " it can be and is done.

If the existing blown in is cellulose this won't be an issue.

Otherwise with blown in fiberglass there will be some compaction which reduces the R value of that material somewhat , however , the negatives will be outweighed by the positives from the R 30 batts.

Another benifit of covering the loose fill with the batts is keeping the loose fill from blowing around in a vented attic.

Besides ..... loose fill fiberglass suffers from reduced R value ( up to 40% reduction ) when in an enviorment of moving air .... such as a vented attic space. Covering the loose fill with the batts will help to offset this negative.

2 cents worth.

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