I'm not familiar with your type of heater, but if it is not a vented type then the combustion will add moisture to the air. Depending on your available electricity, you may want to use a dehumidifier (even with the cooler temperatures). There are other heating options which do not have the humidity issue (vented or electric). One of my favorite forums is the Garage Journal, which has its own heating/cooling section:
http://www.garagejournal.com/forum/f...splay.php?f=26
Be prepared to spend MANY hours there.