Deep blown in cellulose for attic – questions
I have a few questions regarding deep (beyond R60) blown in cellulose for an attic. Cellulose is relatively cheap and I’d like to maximise my attic insulation without causing any other issues:
1. Several manufacturers of cellulose insulation have depth/R-value charts that stop at R60. Is there any practical reason for this, or is it just because most people don’t bother going above R60?
2. Does compression above a certain depth negatively affect the performance of the insulation in any way? I.E. does your R-value/$ go down appreciably beyond a certain depth?
3. Assuming 24″ truss/rafter spacing, what practical limit on depth is there if you want to avoid bowing of the ceiling drywall with both 1/2″ and 5/8′ panels? At what point would it make sense to sheet with OSB before installing the drywall?
4. If sheeting with OSB before drywall, would you put your vapor barrier on the top side, or between the drywall and OSB?
5. If installing a loft floor in the attic trusses for storage (not conditioned living space), how much space should be left between the top of the cellulose and the floor sheet? Is a space necessary?
Thanks for your thoughts.
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