[AHAB]

Modine "Hot dawg" works great.
Look at the International Greenhouse Company Greenhouse Mega Store has everything you need to build, equip, and maintain a commercial, hobby, school or institutional greenhouse. site.
Also Gas Heater - Power Vented - Garage Heaters, Residential Heaters, Greenhouse Heaters, Modine HD100 for the Modine heater I bought the HD 60 and it works very well for my 500 square foot greenhouse.