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Sizing hrv

A7WFOREVER1 | Posted in GBA Pro Help on

I am building a new home. 2100 sq ft  3 bedrooms and a office. The house will have close cell in attic and open cell in walls. So it will be tight. Exhaust air for cooktop and dryer. Plus 400 cfm in total for bathrooms. I am using a Bosch 18 seer inverter unit  I am trying to size up a HRV or a ERV this will be my first time for a complete spray foam new construction house. Building in Swainsboro Georgia.

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  1. Expert Member
    Akos | | #1

    Ventillation rates here is part of building code, I would check your local code. If there is nothing, you can size based on ASHRAE 62.2.

    Here are some links you can read more about sizing:

    https://www.greenbuildingadvisor.com/article/designing-a-good-ventilation-system

    Generally, in most climates you want and ERV. Some places with very humid shoulder season could have issues with mold on an ERV core, in those places and HRV might be a better options.

    In either case, you want the HRV/ERV larger than what is needed. You can use this extra boost capacity for exhausting a couple of bathrooms (saves two or three dedicated bath fans) and to clear the house after deep frying or after a wet dog. 200CFm is probably in the ballpark with the unit running at the lower ASHRE flow rate the rest of the time.

    P.S. Spray foam is something that you generally design out in a new build. There are much cheaper ways to air seal in most cases. There is also this misconception that a spray foam house is air tight. This is not always the case, it easy to have details that allow for a lot of air leakage ie:

    https://www.greenbuildingadvisor.com/question/air-seal-conjoined-trusses

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