4 posts / 0 new
Last post
ET6984
Insulating Return Duct

I have seen other posts on this topic of whether to insulate or not and it seems the overwhelming answer is, insulate. My return duct is in the attic. So, can I wrap it with some left over unfaced-batting from my attic insulation job, or do I need to use special duct insulation? And does it need to be faced with a moisture barrier or unfaced, if so which side does the moisture barrier go on?

Thank you.

TheMaskman
Re: Insulating Return Duct

My return duct is in the attic. So, can I wrap it with some left over unfaced-batting from my attic insulation job, or do I need to use special duct insulation? And does it need to be faced with a moisture barrier or unfaced, if so which side does the moisture barrier go on....

ZZZ
Re: Insulating Return Duct

The codes require insulation, and it is very important for the proper operation of the HVAC system. In the attic, you need a minimum of R-4 on the return and R-8 on the supply ducts. That is the minimum though, I always use R-8 on the return just to make the system more efficient. A vapor barrier is used to prevent moisture in the air from condensing on cold metal duct in the summer, therefore it would go on the exterior of the insulation, to keep the moisture out of the insulation itself. I don't know of a code requiring a vapor barrier on return duct work, but it is necessary if you like in a climate where high humidity will condense on the 72-78 degree metal return duct. I always use it as I feel it makes for a better job.
http://www.energycodes.gov/training/res_wbt/hvac.stm

http://www.energycodes.gov/rescheck/documents/res_review_guide.pdf

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.