[tomatsu]

There are ventilation systems with heat recovery.

They are usually triggered by a timer or humidity, but it would be also possible to trigger them based on VOC or CO2 levels.

Single-room heat recovery ventilation units are relatively affordable (about $400). There are also some which can be integrated into the window frame if drilling a 6" hole into a wall isn't an option.

[mcculley]

I have read about such systems. I have not seen any in Florida. Do they work for keeping heat out while exchanging air? Where I live, we are trying to get rid of heat, not recover it.