Can HRV ductwork (insulated of course) be run in an unheated attic space without creating moisture problems?
GBA Editor
| Posted in General Questions on
I am building a well insulated/sealed house in Interior BC. I am putting in an HRV and I am wondering where the balance is between simple ductwork design and not going thru the attic space in a cold climate. If I do go thru the attic, the runs will be much simpler than if I go thru my second floor and up the wall (than the ceiling in the bathrooms). Local contractor thinks it will be ok but I am worried about problems in the years to come. Thanks.
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Replies
Leigh,
Most HVAC contractors underestimate the importance of duct sealing and duct insulation.
Ducts installed in unconditioned attics face the worst possible conditions. Your idea can work, as long as:
1. Every duct joint is impeccably sealed to prevent leakage.
2. The ducts are insulated to at least R-8. More insulation is always better; you may want to bury the ducts in spray foam insulation or cellulose.
Another option is to build down the second floor ceiling, or build soffits, to keep the ductwork inside the thermal envelope. No problems, no worries.