Whole house venting systems

I’ve come across these whole house continuous ventilation systems in new houses, both stick and manufactured. These are new items and the new owners want to know if they are working. Who has any tips on these things? As houses get tighter and new venting laws are requiring these we’ll see them more.

Test

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http://aprilaire.com/product.asp?ID=C80A4BDAF31E426399117EFAF5F263B5&categoryID=9DDC176A7AD948DCB0D14F348EB3FF1e&catID=

The ventilators work by using a media material to transfer the heat between the incoming or unconditioned air &the exhaust or conditioned air, most are 80-95% efficient they work year round. Little needs to be done other then cleaning the pre-filters and small amount of maintenance