MN,
My thoughts exactly on delivering heat (most to lower level). Here in OKC, we need to also deliver cooling and that needs to be on TOP level. The solution seems to be minisplits, with one at top level and another on the bottom level.
The problem with many ERVs are that they are often too big. One that I have used is only 20 cfm (doubles to 40 cfm with remote low voltage SPST switch). Can be configured to only 10 cfm (and doubles to 20 cfm).
https://www.acwholesalers.com/Panaso...t-ERV/12786.ac
They also make a very nice coaxial ventilation tube meaning only one hole drilled in exterior wall. Thin enough to fit into overhead stud space.
A bit expensive (~$350), but they work very, very well.
I have put them in bathrooms to constantly ventilate at low rates. When the shower light is turned on, the volume doubles thereby ventilating the bathroom (use a DPST switch with one side on 120 V AC for shower light, the other pole to control ERV ventilation rate).
They are not listed for bathroom use, but work very well in that application. Too small for kitchen use. Also absolutely NO noise. You literally cannot hear when they are on. My kind of unit (I hate blower noise . . . . ).
Minimal maintenance - just cleaning out air filter once a year. So far, no field failures and clients love them.
Steve