Energy recovery ventilators are great. Some of these systems have been known to have heat exchange efficiencies as high as 70-80% while others have as low as 5

Energy recovery ventilators are great. Some of these systems have been known to have heat exchange efficiencies as high as 70-80% while others have as low as 50% It is subjective and anecdotal, but I am now more productive and I sleep better with a bunch of ERVs installed in my house. https://en.wikipedia.org/wiki/Energy_recovery_ventilation https://en.wikipedia.org/wiki/Energy_recovery_ventilation