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HRV internal ductwork ....does it need insulation?

I understand that any ductwork connecting to the exterior of the building will need insulation (to prevent condensation). Do I need to insulate the internal ductwork that carries the air to and from my rooms? I was planning on just using 6" vinyl ducts. THANKS.

Posted Fri, 02/07/2014 - 14:18


3 Answers

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There is no need to insulate ventilation ducts that are located within your home's conditioned envelope. The only exception is the fresh air intake duct that connects the HRV to the outdoor port. Because this duct will get cold in the winter, it should be insulated. Many installers use insulated flex duct for this section of duct.

Note that most ventilation experts advise avoiding PVC (vinyl) pipe for fresh air ducts, because of possible off-gassing concerns. Galvanized ductwork is a better choice.

However, you can use use PVC pipe for exhaust ductwork if you want.

Answered by Martin Holladay, GBA Advisor
Posted Fri, 02/07/2014 - 15:19
Edited Fri, 02/07/2014 - 15:20.

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The exhaust duct should also get insulation - the more efficient the HRV, the closer to outdoor air temperature the air in this duct will be. Agreed on the interior side though, no need for anything special here.

Since the concern is condensation on the outside of the duct, be sure the insulation has a vapor barrier facing on it as well (or be entirely vapor-impermeable, like a closed-cell foam wrap), otherwise moist air will still be able to come in contact with the duct surface. And tape the seams, etc, so it's a continuous barrier.

Answered by Cramer Silkworth, PE
Posted Fri, 02/07/2014 - 18:33

Helpful? 0

Thank you Martin and Cramer. This answers my question. I'm happy to save insulation and use it where it matters the most.

Posted Fri, 02/07/2014 - 20:34

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