I got pretty heavily involved in energy saving in the last oil crisis (Carter days). The trick with fresh air makeup is a heat exchanger that scavenges the heat from the air going one way and transfers it to the air going the other way. Granted you only save half the energy as a theoretical max but that is better than zero.
In reality the efficiency of most heat exchangers you might have in a dwelling wasn't worth the expense and hassle but I have seen it done in big commercial fairly successfully.
The National Geographic building in Germantown Md heat exchanged everything and used water as a transfer and storage medium. They ended up with so much excess heat from normal building loads they could keep the building warm and still had enough left over to keep the lake out front from freezing.
