Burying ducts with insulation board
In an unvented attic in Climate zone 1A would it be acceptable to create R13 around flexible R6 ductwork by boxing around flexible ductwork with equivalent of R13 insulation board ( 1″ Sika R Max R6+150 Owen corning’s Foamular 150=R10 underneath the sika board for R16 Total)? Also, instead of having these boards on the bottom could 6″ of fiberglass batt insulation be used so box around duct would have insulation board on top and sides and 6″ of fiberglass batt insulation on bottom? Joints would be sealed with caulk and great stuff pro with fire block. Finally ducts would be buried with at least 4 inches of blown in insulation.
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Did you read this article?
Do you understand the risk of condensation?
Yes, but the article doesn't really address this type of system. If the attic ducts are air sealed off from the attic in basically its own little ice chest and I don't see how the duct could condensate. Has there been any research done on this? Thanks for you reply.