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Community and Q&A

CZ5A Whole House Ventilation Design

megapointe | Posted in Mechanicals on

Greetings GBA,

I have a 1940s home that I recently removed the gas fueled forced air HVAC system from (and all its ductwork) and replaced with a 3 ton Fujitsu heat pump system. That work happened about a year ago and I found that the heat pump had a difficult time heating the house in the winter especially when exterior temperatures reached zero or lower. To remedy this I am planning an energy retrofit of my envelope by injecting spray foam into my exterior walls and spraying open cell foam on the underside of my roof. My hope is that the new airtight and better insulated enclosure will allow for my heat pump system to perform exceptionally better in all seasons.

Because my old leaky house will be more air tight and my heat pump system does not bring in any fresh air I am looking to install a whole house ventilation system. I’ve done quite a bit of reading and still cannot determine whether I’ll need an ERV or HRV. In the winter my house is definitely very dry but I attribute that to my home’s envelope being very drafty. If I air seal and insulate I might have a house that is more humid in the wintertime.

Am I overthinking this or not thinking about it correctly? Would you recommend an ERV or HRV? Any brands you would personally recommend?

To add to the equation is the fact that I am likely going to be installing two dedicated systems. My house is a single story home with a basement. I plan to install the ERV (or HRV) in the attic space to serve the main floor of my house and install a second system to cover the basement. My thought process for this is that I do not have a space to pass ductwork from the attic down to the basement so I’d prefer to just have two systems dedicated to each. Additionally, I’m installing a heat pump water heater in the basement that will likely dehumidify the basement. 

Now, with THAT information in mind does your original recommendation change at all? I really appreciate any feedback the GBA community can offer. Thanks so much.

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  1. megapointe | | #1

    After doing some more research it looks like this Honeywell ERV could fit the bill if I go the ERV route. Given my house is ~2000sf and 3 bedrooms it seems this system alone could work for the entire house. Maybe there's still a solution for routing ductwork to supply all the rooms if I install the ERV in the basement. The only challenge will be sending stale air back to the ERV and then outside. It seems like that is ideally done from overhead - especially in kitchens and baths - but getting ductwork up to the attic from the basement would be a real challenge in my situation.

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