When calculating return air grille size, do I add up all the return air grilles, or does the calculation only apply to the main return? I have 5 total (2 main floor bedrooms, 2 in finished basement, main return in living area). I’m putting new hardwood down and I’m about to cut the hole for the main return.
Return air size
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It all counts but you have to take into account the smallest measurement - maybe the grill is bigger than the duct, so you would have to calculate based on the duct cross sectional area. Overall, return area should be 100-150% of vent area.
Thanks for the info. All four return vents I mentioned above are 6”x14” off of an 8”x12” duct. The main return at issue can be cut anywhere between two 24” oc joists. The duct leading to sheet metal between the joists is 8”x9”. The main return grille that the mechanic put it initially is 8”x24”. I’d like to go as small as I can due to the location. My furnace is 80,000 btu and the conditioned area is about 2000 sq ft including basement. I’m not sure if that’s enough info to make a suggestion...but given that the duct leading to the vent is 8”x9”at its smallest point, am I right to think I can get a floor vent close to that size?
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