HRVs and ERVs are for fresh air ventilation in well insulated buildings. They save energy over a simple vent by transferring heat (or lack of heat) from stale c

HRVs and ERVs are for fresh air ventilation in well insulated buildings. They save energy over a simple vent by transferring heat (or lack of heat) from stale conditioned exhaust air to incoming fresh air. I think ERVs also deal with moisture. A separate device called an air-side economizer can be added to a central air conditioner system. It can save energy when it’s colder and dryer outside a building than inside. When conditions are right, cold, dry outside air is pulled in and warm building air is exhausted reducing the need to run the AC compressor. Air-Side Economizer | Products | ENERGY STAR https://www.energystar.gov/products/low_carbon_it_campaign/12_ways_save_energy_data_center/air_side_economizer https://www.energystar.gov/products/low_carbon_it_campaign/1...