Seeking advice on adding HVAC air return ducts

10 days ago
last modified: 10 days ago

We're upgrading our HVAC return ducts as part of a kitchen remodel. It’s a two-story 1958 build. 1750 square feet. Primary goal is to get our system up to code with sealed return ducts that don’t draw any garage air. Secondary goal is to improve upstairs cooling, if possible. Grateful for any advice. System details:

1. HVAC system is a 6.5 ton furnace and a 3 ton AC unit.

2. House has two first-floor air return “ducts.” (Actually unpanned ceiling joist cavities) Total return duct size is 117 square inches. Total return grill size is 328 square inches.

3. There is no second-floor air return.

4. Supply is probably inadequate. I’ll make a separate post about that. For current purposes, I’m asking what the best air-return solution is, assuming adequate supply.

Our contractor’s HVAC guy is proposing two solutions

1. Add a second floor return, near the ceiling, in the center of the upstairs hallway. Increase first-floor return grille size. OR

2. Add an additional downstairs return duct, and increase grille size on all return ducts, to an amount adequate for the whole house. No return upstairs.

Adding the upstairs return will be more expensive and more disruptive during construction. It also will eliminate a linen closet. DH is asking whether an upstairs return is really worth it. Could we get substantially better upstairs cooling by just increasing the downstairs return capacity? Possibly with a ceiling fan at the top of the stairwell to promote airflow between floors?

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