Is it more cost-effective to insulate a roof plane or use SIPs?
I am planning to condition our attic and use it as a bonus office/studio space in the house I am designing. The house will be a basic 44x30 rectangle with a full gable roof. Despite the known issues with skylights, we will probably install a couple of skylights on the north side of the roof to bring light into the space. I am building in Zone 6, and would like to have an R-Value of at least 45-50. I do not want to use spray-foam and would need to figure out a solution that involves some combination of rigid foam (probably exterior) and cellulose or rock wool insulation of one sort or another.
What I am trying to figure out, is whether it would be more cost-effective to use 12" SIP panels for the roof or to insulate the roof planes. It is of note that I will not be doing the work myself. There is also a possibility that the whole thing either way would be too expensive and we will just have to settle for a non-conditioned attic (with no vents or pipes running in it).
Can anybody chime in on a) whether they think SIPs or Insulation would be more cost effective and b) Any geusstimates on cost of having a conditioned attic vs. unconditioned ($5,000, $10,000, $20,000, etc).
One final thought - the SIP dealer mentioned that SIPs won't require as much truss support as a standard roof, which might reduce the cost a bit, as well, though floor joists would be required at that point.
Posted Jul 3, 2014 3:25 AM ET
Edited Jul 3, 2014 5:33 AM ET
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