Community: Mechanicals

For proper air being returned to the HVAC unit that is the size of the duct have to correlate to the size of the grille for the return air? So for a 12 inch air filter grille what is the largest size return duct that could be attached to that for proper operation?

I’m getting air pressure coming from the attic through the switches ,outlets ,and around the drop ladder in a different zone than the one with what I believe is undersized return.

Thanks Rich

I have a three-bedroom house, one bathroom, in Worcester, Massachusetts. It was built in 1947, and measures 1,100 s.f.

After purchasing it, I decided to upgrade the insulation in the walls and in the attic and air seal the home, and install new windows. All which was done through the Mass Save program. After completing, all the energy bills went down.

But the problem now is the house has high humidity and seems to be too tight and cause hard breathing. I have noticed mold that I did not have before. Also get headaches more often than I used to.

Curt Kinder is an HVAC contractor who understands building science principles -- and that type of HVAC contractor is, unfortunately, rare. Curt lives in Jacksonville, Florida, and he often posts comments on GBA.

Curt is helping to raise the bar on building science knowledge in his profession. He was recently interviewed by public radio station WJCT. If you want to hear some of his advice to Florida homeowners -- it's good advice -- visit this web site: Going Green.

I'm building a 4 bedroom passive house with about 3,200 sqft of conditioned space including a home office and a 2 car garage and 1 car garage (workshop) totaling around 800sqft. I would like to use an 8 zone mitsubishi system with horizontal ducted indoor units. Zones will be assigned to each bedroom (zones 1-4), the home office (zone 5), the main living area (zone 6), the 2 car garage (zone 7), and the worshop (zone 8).

I have a few questions: