On 2007-11-23, Joseph Meehan wrote:

If you start with 80º interior and 60º exterior the best you can do is
to get 70º air coming into the home and 70º air exiting the home.

In a contra-flow heat exchanger, I believe you can get 100% heat
exchange, i.e. the air exiting the house is 60 degrees and the air
entering the house is 80 degrees.

Cheers, Wayne