Manual J wants 10 CFM to a room…possible?
Some of the rooms in a Manual J heat load required air volume velocities as low as 10 CFM coming out of a duct. I’m not an HVAC pro or even a construction professional – just a homeowner having issues with temperature variation, high static pressure, lack of return air, negative pressure, high dust, and unsealed/inaccessible ductwork. I’ve done all these “energy efficient” things but at the end of the day, I feel less comfortable & temperature variation is a lot greater than what it was.
I’m trying to go by the book and follow the Manual J recommendations but the first few HVAC contractors have told me 10 CFM isn’t possible to achieve (I’m considering just redoing all the ductwork). I hate being in the position where the energy auditor tells me one thing & then the contractor says things don’t happen like that in “real life” and I have to either fend or give in. Feels like if you’re not building a house from the ground up with energy efficiency in mind, it’s impossible to get it right after the fact if you’re just a homeowner who has to go out & seek various contractors.
Going off on a tangent. I even have a small area that requires 1 CFM. So what do I do? Keep looking for an HVAC contractor who can read a Manual J & be confident in delivering what it says or settle because the Manual J has unrealistic numbers? Is 10 CFM even noticeable???
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