I am currently considering heating my garage but dont know if I should heat it from my furnace or choose another method as I am not too familiar with it. My trunkline runs right behind my garage wall therfore all I think I would need to do is go straight from the supply approximately four feet thru the wall to my garage. I was also wondering about the return? my garage is approximately 750 sq ft and is attached to house. Any help would be appreciated as you can tell I am a rookie....