Replies

1. GBA Editor
   Martin Holladay|Dec 12, 2012 07:32am|#1

   Sylvia,
   Most HRV ducts are small-diameter ducts, and it isn't that hard to locate all of your ductwork in partition walls.

   Here's a link to an article that should provide you with useful information:Installing a Heat-Recovery Ventilator.

   In that article, David Hansen wrote, "To keep airflows as high as possible, we use 6-inch duct for stale-air pickups. For fresh-air supplies into bedrooms, 4-inch ducts are usually adequate. We use mainly 30-gauge galvanized ductwork. In 2x4 partitions, we use 6-inch oval duct, which measures 3 1/2 x 7 1/2 inches and comes in 5-foot lengths. Oval duct has a smaller airflow capacity than round but is perfectly adequate for the individual wall stacks. Each register mounts in a 6x10-inch stackhead, a duct fitting that makes the transition from a rectangular register to oval duct."

2. 
   Sylvia Ettefagh|Dec 12, 2012 10:50am|#2

   Thanks Martin. I have another question- the full length of my house has a cathedral ceiling in the front half (great room and one bedroom) and an attic in the back (above a bedroom, bathrooms, mechanical room... ) Given the cathedral ceiling and the climate zone, I plan on insulating the roof on the outside of the sheathing to move the dewpoint up. In this case is the half that has an attic space above it considered conditioned? would it make sense to run the ducting through the attic?