When a house has a ventilation, the questions are:
1) how effective is the heat exchanger?
2) how often should the ventilation work?
There is no 100% effective heat exchanger…
A ventilation should anyway not work all the time: noise… and loose of heat.
Therefor, with 4 temperature/humidity sensors, two relays, an arduino board and over 300 lines of C++ code… the ventilation is now optimised accordingly to the outside temperature
(If you want to try too, I would share my own code for inspiration)