Reducing house humidity in a mild, humid winter climate
I'm in SW coastal BC and none of the houses here have humidifiers (unless some clever HVAC salesperson manages a needless sale) precisely because the climate is so wet (one can assume that RH outside is pretty much saturated for the whole of winter). Home relative humidity was in the mid 60% range but apparently increased to high 60s since some leaky patio doors were replaced. Heating is with a heat pump so the vent air is not dehumidfied.
I was thinking of using a dehumidifier but that can be inefficient. With an air exchanger, what should the RH drop off if the house temperature is 19-20C and outside air temperature is anywhere from 0-7C but pretty much saturated?