Designing airflow in large low load homes


I am looking for some feedback: I am working on a 3850 sq ft house in So. Cal., Castaic to be exact. It will be well insulated and air sealed (blown in blanket [fiberglass] in 2x8 with an R-4 continuous on the exterior. It has a 44' long x 22' high x 23' wide Kitchen-Great room with a cathedral ceiling. Manual J calls for only 340 CFM total, but how to throw that all the way across the 44 ft long room to achieve adequate mixing in such a cavernous space? Even a tiny 12x4 (Truaire) only has a throw of about 30 ft and that is with a NC of 40 which is starting to make audible noise. Thoughts suggestions? 

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  • Hi there

    A suggestion that might be a bit outside-the-box: might this be a situation resolved by the old paddle bladed ceiling fan technology?


    • Thanks Eric,

      The room will have a fan, but... I am not a fan (pun intneded) as runing ceiling fans add heat to rooms. I would like to be able to design correctly without additional inputs. 

      Unfortunately, there will be no Coanda effect b/c the register airflow will still be in the middle of vault, not next to the ceiling. I wish I could put the register on the side walls, but due to the vault, it would be a really long run around and defeat the purpose of getting the air into the conditioned space.   

  • Look up Coanda effect and the concepts of distributing air along surfaces. 

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