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boogerhead_gw

Using PolyISO sheets for Trunks and reducing the duct size

boogerhead
15 years ago

I read several articles that cover the aspect of making your residential HVAC ducts from sheets of PolyISO. It has an R-value of 5 per 3/4" and is also foil-faced. Using 2 sheets will give me the 1.5" necessary to fit standard adapters. The foil will be on both the inside and outside of the duct and it will have a resulting R-value of 10. Has anyone done this before?

Also, would it be better to reduce the size of the trunk line in steps (i.e. 10' of 12x14, then 10' of 8x12, then 5' of 8x8, etc) or would it be best to have a gradual reduction the entire length of the duct (i.e. the duct would be 12" wide for the entire length but would slope from 14" to 8" over the 30' span). While this sounds difficult, using the PolyISO sheets makes it completely possible.

Any input or advice here ?

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