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Community and Q&A

ERV/whole house dehumidifer

Roger_S39 | Posted in General Questions on

i) Is there a product that does both functions in 1?

IE: is there a product that does the function of both an ERV and a whole house dehumidifier? 

ii) Or, do you need to install an ERV (ideally a” Multi point ERV with Full Connection to Central Air Handler”) and a separate whole house dehumidifier, if you want both functions in a home?

iii) )Is there any reason why you wouldn’t install both units, attached/integrated to a typical central air (furnace + AC) system?

iv) If the “1 ton of AC per 400-600 sq. ft.” method is used (instead of completing the manuals J,S,T,D) for designing a new system to be installed in a new construction home, – is it even worse to do that when either an ERV or whole house dehumidifier is present (in other words does the addition of an ERV &/or whole house dehumidifier make the usage of 1 ton of AC per 400-600 sq .f.t method even more “concerning”)?

Thank you.

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  1. User avatar GBA Editor
    Brian Pontolilo | | #1

    Hey Roger.

    I'll let others with more mechanical experience help with most of your questions. However, you could look into the CERV ( or Minotair ( units. They are both multifunctional air exchangers.

  2. Steve Knapp CZ 3A Georgia | | #2

    Hi Roger,

    Are you building new or updating an existing house? Either way, where are you in the process?

    In general, you want to have enough information (blower door test and HVAC metrics) to make good decisions. WAGs may work out--or not.

  3. User avatar Expert Member
    Dana Dorsett | | #3

    >"iv) If the “1 ton of AC per 400-600 sq. ft.” method is used (instead of completing the manuals J,S,T,D) for designing a new system to be installed in a new construction home,..."

    I you use the ton per 400-600' rule on NEW construction you need to have your head examined (seriously?) ! Even many of the rule-of thumb hacks have evolved to a ton per 750' for new houses, which still reliably oversizes it by a significant margin.

    A ton per 1000' would be a better (and still imperfect) rule of thumb for new construction.

    I recently reviewed a proposal for a 2.5 ton ducted Fujitsu for retrofit on a 1960s slab on grade ~1400' house in CA, which is about a ton per 550'. The Manual-J isn't in yet, but that house can probably do just fine with the 1.5 tonner, despite the fact that the ducts and air handler are above the insulation in a vented attic. The advice was to reject the proposal and get a disinterested third-party's Manual-J. Even though it modulates over a decent range even at 82F, it won't modulate much at that oversizing factor. It would be more comfortable with the 1.5 tonner, and probably more efficient too.

    No matter how ridiculously oversized the AC is, it is neither or better or worse from a comfort & control to also have an ERV &/or whole house dehumidifier in the same house. Efficiency wise there may be minor/negligible changes.

  4. User avatar Expert Member
    Michael Maines | | #4

    I'm interested in trying a Minotair Pentacare V12 for this scenario. Instead of a conventional core it has a heat exchanger that allows you to dial in the relative humidity you want while getting full ventilation. It can also control a Mitsubishi mini-split system, so you get all of the heating and cooling you need.

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