I just got done installing this into my workshop (2 car garage):
Ventless, and mounted to the wall
[ame="http://www.amazon.com/Mr-Heater-Propane-Flame-VF30KBLUELP/dp/B000UPR5TY/ref=sr_1_6?ie=UTF8&qid=1288451899&sr=8-6"]Amazon.com: Mr. Heater 30,000 BTU Propane Blue Flame Vent Free Heater #VF30KBLUELP: Kitchen & Dining@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51Bm0coIt%2BL.@@AMEPARAM@@51Bm0coIt%2BL[/ame]
And in my "office in the corner of my garage (8ft x 12ft) I installed this on a thermostat so it won't ever drop below 45 degrees... I store my paint and glue and such in the office, this makes sure it doesn't freeze. For the space this guy rocks.
[ame="http://www.amazon.com/Electric-Baseboard-Convection-Heater-White/dp/B0011TULHQ/ref=sr_1_47?s=home-garden&ie=UTF8&qid=1288452098&sr=1-47"]Amazon.com: Electric Baseboard Convection Heater 36 Inch White: Home & Garden: Reviews, Prices & more@@AMEPARAM@@http://ecx.images-amazon.com/images/I/21AqrwLIK3L.@@AMEPARAM@@21AqrwLIK3L[/ame]
Hasn't gotten ridiculously cold here yet, but both options took the chill out of my INSULATED garage very very quickly during their maiden voyages.
Good luck!