Thoughts on adding AC/Heat to attached garage.

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What are people's thoughts on adding AC/Heat to your garage? I have a newer home with a three car attached garage and have been considering putting a few ducts in it from my existing HVAC system.

The whole idea happened when visiting my brother in TN. His garage has AC and I must admit it was quite comfortable in there. Obviously coming and going during the afternoon with the door open it would get quite warm in there. But with the door closed for a few hours or first thing in the morning, it was nice and cool in the garage.

I could really see myself doing oil changes or maintenance on things especially in the morning.

Heat during winter would also be great.

Garage ceiling would be easy to access to add additional ducts as well as access to my air handler.
 
Add a separate unit that does both heat and air like a ductless split unit. Your home HVAC is not designed to heat/cool the garage. The rooms you split the ducts from will never be as comfortable as they once were. The garage may be slightly better but the other rooms will suffer.

A previous owner to my current home did what you are talking about to heat & cool a small enclosed back porch. It would never heat up or cool down satisfactorily nor would the room the duct was spliced from. I had to pay someone to remove the duct to the porch and patch up the duct in the room where it originated.

I'm talking about an enclosed porch area about 8' X 15' much less a three car garage. FORGETABOUTIT!
 
Using the house HVAC in the garage is against building code. Risk of carbon monoxide getting into the house, and a fire hazard (any walls or ceilings that are shared with the house need to have drywall, I think 5/8", as it has a 20 minute fire rating). Having an air duct going from the garage into the house is like an express-lane tunnel for fire to travel through.
 
Wait until the end of cooling season and buy some cheap window units when they go on sale? I've thought about doing that.
 
It will work ok only if the duct is run right from the main supply plenum. If it is split from a duct supplying air to a room, the room will suffer and the garage will not get comfortable.

Regarding building code, yes there are valid reason to keep the garage space separate, but as long as the owner understands the risks, they are free to do whatever they want. It's their house.
 
I would do ductless split system. It's cheap and very easy to install if you can pull a 220volt line to the condenser outside.
 
Originally Posted by RTexasF
Add a separate unit that does both heat and air like a ductless split unit. Your home HVAC is not designed to heat/cool the garage. The rooms you split the ducts from will never be as comfortable as they once were. The garage may be slightly better but the other rooms will suffer.



Exactly....your home's system is optimized for the home. A separate system is what you're looking for here.

When I lived in MT, had a heater in the garage and kept it around 40°F / 5°C during winter for easy starts. In TX you have the opposite, a need for cooling so in your place I'd just put in an A/C unit. However if you want heat as well, a heat pump may be what you're looking for.
 
If nobody's home, I'll just leave the door open to the garage to let some heat in from the house during the winter.
 
Originally Posted by FADEC
What are people's thoughts on adding AC/Heat to your garage? I have a newer home with a three car attached garage and have been considering putting a few ducts in it from my existing HVAC system.

I have a 3 car attached garage, and have evaporator cooling with upduct discharge into the attic. It's unbelievable how cool it keeps the garage and attic. I don't know what your relative humidity is where you're at? Evaporative cooling doesn't work very well above a 55 degree dewpoint.

Here it rarely gets near that. Yesterday the relative humidity was around 7%. With a cool attic the home A/C unit doesn't have to work nearly as hard. And once the Sun sets the attic stays cool all night. Evaporator cooling is very inexpensive to both install and run when compared to A/C. My garage has almost 2/3rds the sq. footage of my house. So if I air conditioned it would all but double my electric bill in the Summer.

It doesn't get cold enough around here to worry about heating the garage.
 
I have two things: 18,000 BTU ceramic (wall mounted) thermostatically controlled gas heater (from TSC) and a free standing (on wheels) air conditioner. Those AC's have a flexible duct hose similar to a clothes dryer … so I put in a little dog door in the offside garage door to eject heat from the hose. That portable AC is 8000 BTU (Home Depot)

Also, glued 3/4" foil covered foam on the inside of garage doors (cut in panels to let door hinge)
 
It's against code to add ducts to a garage, now if you think about adding supply-only ducts you'll depressurize the living area (drawing outside air in through the walls, windows, doors) which is dumb.


Answer: Buy a mini-split for duct free heating/cooling of your garage.

A mini-split will be infinitely more efficient than any stand-a-lone option.
 
Last edited:
Originally Posted by KrisZ
Regarding building code, yes there are valid reason to keep the garage space separate, but as long as the owner understands the risks, they are free to do whatever they want. It's their house.

That is simply not true. Do you understand the purpose of building permits and having work inspected? Do you know what happens if you do work that's not permitted and it's found to not be up to code?
 
Originally Posted by exranger06
That is simply not true. Do you understand the purpose of building permits and having work inspected? Do you know what happens if you do work that's not permitted and it's found to not be up to code?

Insurance not paying out in case of fire, or issues when one goes to sell the house (and the buyer wants it fixed or they back out)?
 
Originally Posted by exranger06
Originally Posted by KrisZ
Regarding building code, yes there are valid reason to keep the garage space separate, but as long as the owner understands the risks, they are free to do whatever they want. It's their house.

That is simply not true. Do you understand the purpose of building permits and having work inspected? Do you know what happens if you do work that's not permitted and it's found to not be up to code?



Yes I do. You get a permit so that the city knows you are upgrading your house and will reassess the value of your home very quickly so that they can collect more property tax from you.
All under the guise of safety.
 
Originally Posted by KrisZ
Yes I do. You get a permit so that the city knows you are upgrading your house and will reassess the value of your home very quickly so that they can collect more property tax from you.
All under the guise of safety.

So you'd get a permit to run a hose from your exhaust pipe to your bedroom? Sounds like the same thing to me.

All under the guise of safety of course.
 
Originally Posted by kschachn
Originally Posted by KrisZ
Yes I do. You get a permit so that the city knows you are upgrading your house and will reassess the value of your home very quickly so that they can collect more property tax from you.
All under the guise of safety.

So you'd get a permit to run a hose from your exhaust pipe to your bedroom? Sounds like the same thing to me.

All under the guise of safety of course.


Yup. I would just not connect the other end to a tail pipe at the time of inspection. It would pass with flying colors as a fresh air intake under the guise if safety because my pet is asthmatic.

I've seen my new house being "inspected" and have friends in the construction business that confirm what I saw with my own eyes.
 
As has been stated, running ductwork from the house's HVAC system is a very bad idea for several reasons. You don't want any way for CO2 from the car exhaust to get back into the house, not to mention chemicals and odors from other "garage" type activities such as spray painting.

Originally Posted by KrisZ
Yes I do. You get a permit so that the city knows you are upgrading your house and will reassess the value of your home very quickly so that they can collect more property tax from you.
All under the guise of safety.


No you don't.
While assessment value is just one portion of the reason for a regular homeowner, safety is another (more important) reason. For example, if some doofus chooses to rewire his home, does it incorrectly and it catches fire that's a safety issue for everyone in the house. And if that fire spreads to the neighbor's homes, it's a safety issue for the others in the neighborhood as well. Especially for those neighborhoods that have very little room between houses, or have row houses/townhomes.

Any work I have done in my rental units is inspected by the city-it has nothing to do with the property value, but the safety of the potential renters. Anything that is not up to current code is corrected, again for the safety of the renters, not for property tax purposes.
 
Fire code is pretty strict and treats your garage as separate isolated building.

You could drop the $3k-$4k ductless split unit to heat/cool your garage independently. I know a few people who have this and very happy with them even in garage.
 
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