Blown-in cellulose In attic above garage ceiling
I will be installing air conditioning in my garage, but first would like to insulate the attic above my garage ceiling, which is currently not . I would also like to install a plywood floor over some of the area, which will be used as storage space. It looks like blown-in cellulose is the best way to go. The insulation company has offered to add either 6.5″ for R19 or 10″ for R30. The problem is that I only have a cavity depth of 3.5″, as I have trusses with 2X4’s (24″ spacing).
My question is whether to ask them to blow in only 3.5″, or to overfill the cavity and lay the plywood on top, thus compressing the insulation. The best thing I can find is the attached chart. It seems to be saying that 10″ of loose fill will produce the equivalent of 3.5″ of dense pack insulation, which would result in R-13–about the same as 3.5″ of loose pack. So I should have them just blow it in to the top if the 2X4’s, and not overfill.
Is this correct, or am I missing something? Advice would be appreciated.
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