Low-slope roof insulation questions
Q1. Can existing loose fill cellulose be dense-packed later?
Q2. On a vented low slope roof with loose fill cellulose on the attic floor, will rigid foam above the decking create issues?
I just read Martin H’s article on this (Insulating Low-Slope Residential Roofs) and live in a Philly row home. Our “attic” slopes from about 4′ to about 8″ between top of ceiling joists and the bottom of roof joists. We had a min. of 8″ of cellulose (r30) blown in( not dense packed) over minimal existing insulation and we have a couple mushroom vents on the roof. So it’s currently a vented low sloped roof but probably not adequately vented at the moment.
We’re planning to install solar pv and considering a roof tear-off and replacement with tpo. I understand they like to install tpo over rigid foam and I’d love to benefit from that insulation but I want to prenvent condensation conditions.
Would it make sense to dense pack the inaccessible part of the ceiling from above after the roof tear off so that portion of the roof would be unvented and benefit from the rigid insulation? Can that be done?
I’m thinking I should then just add venting on the high side of the attic and rely on the loose cellulose for insulation since Bruce Harley states in the article that he doesn’t advise dense packing an entire attic with significant changes in fill depths because it can be hard to dense pack the deeper sections. I don’t expect the rigid insulation to be of any benefit on the vented portion of the roof, would it create issues?
Anything else I’m missing?
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