>> In the past HRVs were mostly used in colder climates > Did you mean warmer climates? No: HRVs were in cold climates previously because HRV do not deal with

>> In the past HRVs were mostly used in colder climates > Did you mean warmer climates? No: HRVs were in cold climates previously because HRV do not deal with moisture, and so there was less frosting / icing up of the membranes. ERVs were more focused in warmer climates, because warmer climates tend to have a lot of humidity, so if you had a dehumidifier in (e.g.) Texas or Florida, and you exhausted stale air, it would end up exhausting the conditioned drier air and intake the outside humid air, which you would then have to dehumidify again. Of course ERVs are also desirable in cold climates because cold air is dry(er), so you'd be drying out your house. So now that is technically more easy, ERVs are also being used in colder climates.