Heating my garage with existing main duct

I've just had my furnace replaced and it sits in the heated side of my basement (just a small boot tied into the main duct right off the furnace so it's not as warm as the rest of the house due to 3 walls being concrete with small casement windows...not really my question here though). At any rate, the other half of my basement is a slightly oversized (width) 2 car garage that sits directly under the living room and dining room/part of the kitchen. When the "comfort specialist" from the plumbing/HVAC company was in the garage with me and saw my project 68 camaro in the garage he was asking me questions about the work I'm doing on it. When I told him I don't get to work on it in the winter months due to the cold tempatures in New England and he notice that the main duct for the heating/air conditioning went right along the ceiling and said he'd just tap into that to heat the garage. There is insulation around the ductwork and it's sheetrocked around that as well. I don't want to simply just punch into it and install a register (boot I think is the term?) and then have the cold air from the basement during the system "off" times enter into the kitchen/dining room above - hindering the efficiency. My thought, though is that, if I did punch into it, I could have it be a manual damper type that I can close when not in use to keep the efficiency of the house. From what I've read on this forum, though, one idea is to pipe the top of the main duct and put ceiling-down registers, but getting into that ceiling is nothing I'd be looking forward to doing, since I really don't want to make any mistakes with my living area right above. I have to tried to explain the situation such that it's easy to picture the setup. What would be a good approach to this? Are my fears of losing efficiency valid if I were to just put a large (or two smaller) registers? The heat is forced hot air from natural gas. The two car garage has two standard sized garage doors and one standard access door in the middle of them. The only door used daily is the side with my daily driver in it. Thanks for any advice.

 

Not an expert...but I'm pretty sure there a rules (as in you can't!) about heating the garage with the home heating system.

Lets see if I'm thinking correctly.......Pro's?

 

Now I've just thought of another concern: I don't warm up the daily driver in the garage, but I (obviously) start it in the garage, what about the exhaust from that getting into the rest of the house. Along those lines, I do store gasoline, used motor oil, etc. in the garage so there are elements of concern there as well. By the way, I left out the fact that 3 sides of the main duct are "exposed" meaning I can see the sheet rock that surrounds the duct and that it is in the center of the garage ceiling. Thank you!

 

Thanks, gunguy...that seems to validate my concerns of fumes. I don't know a great deal about HVAC in general so I'm not sure. I keep thinking there is something about a positive pressure, so the exhaust, etc. wouldn't be allowed to enter the system and house, but I don't know. I'd really like to hear from an HVAC expert and may just scrap the idea based on that. I certainly wouldn't want to do anything to jeopardize the health of my family.

 

I don't think its just fumes, I think it has more to do with flame spead in the even of a fire.

 

you are both on the right track, it is both fire and fumes. Plus opening up an exit for the plenum means the return will have to find more air somewhere (from outside) which as you stated will reduce your efficiency.

Even just a quick start each morning and pulling the car out into the driveway to warn up produces a huge amount of CO.

You've got all the answers, so I'll go away.

"my project 68 camaro" Those were the dream years for me.

Bud

 

Thank you both very much. I'm scrapping the idea. I think the "comfort specialist" from the Plumbing company that installed my furnace should be careful with that type of advice. I may figure out another way to heat it one of these days, but keeping my home safe for my family is obviously my number one concern. You guys have helped a great deal and I appreciate it. Thanks again.

 

Absolutely not. Bad idea. No matter what combination of dampers fans and controls you have its not safe and against the codes everywhere.