If the windows are open when the weather is pleasant, (possibly allowing pollen and humidity to enter) what is the purpose of the dampers?
Since blower door tests allow the capping of ERV intake and exhaust grills (as the ventilation system would be in balance during occupancy, unlike dryers and chimneys), this isn't that big a problem.
While it is true that balanced ventilation provides continuous circulation of filtered fresh air, it isn't entirely accurate that thermal stratification and room-to-room temperature variations can be overcome by the ventilation system.
This is because the amount of air required to provide acceptable indoor air quality is a fraction of the amount of air required to deliver heating and cooling. I designed the continuous flow rate for ProHome to be 120cfm. I suspect the flow rate for the 2 ducted minisplits may be 3-4 times that.
This is what allows Zehnder to use small (3" diameter) flexible duct work and low flow rates. The many advantages include nearly silent operation, but that low airflow cannot be expected to even out temperature differences - the responsibility of the heating and cooling system(s).
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