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Discussion Starter #1
Hello all.

I'm sure this has been covered in scope but I have a specific question about my system and room. I have an attached 2 car garage that I am using as a workshop...well at least as long as cool temps allow. My HVAC is located in the garage in one corner and it seems it would be easy to add a supply vent in one of the main trunks coming off of the unit but I'm not sure which is supply and which is return. I won't be adding a return because of products I might be using in the garage. I plan to insulate the overhead door and blow-in insulation in the space above the garage which is decked storage.

www.crenshawweb.com/hvac.jpg

Here is a quick sketch of the setup. I know I could add a couple of supply vents in the ceiling but I like the convenience of having the vent by the door so I can control it as I walk in or out of the garage. Assuming I can determine which is which, would it likely be a duct within a duct? If so, is there a special type vent I would need to accomplish this? Any help would be much appreciated.

Mark
SW Indiana.
 

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My HVAC is located in the garage in one corner and it seems it would be easy to add a supply vent in one of the main trunks coming off of the unit but I'm not sure which is supply and which is return.
Right off the bat, you're going to face the issue that your HVAC system is sized and balanced for your house, minus the garage. If you add a vent (esp. in your main trunk) in the garage, you're depriving the rest of your house of that heated (or cooled) air.

You might find that your house doesn't get hot enough in the winter, or that your unit is struggling to keep up with the added load of the garage. This is especially true in a 2 car garage -- a lot of heat loss around the garage door(s), even if you insulate/weather strip as well as possible. The R value of insulated garage doors is almost always going to be less than that of a house wall.

I won't be adding a return because of products I might be using in the garage. I plan to insulate the overhead door and blow-in insulation in the space above the garage which is decked storage.
If you're going to be using hazardous products and/or generating sawdust, then a return into your main HVAC system is definitely not a good idea. However..

With no return, you're basically taking nice heated (or cooled) air from inside your house (via the house's return), and ejecting it into the garage, and then to outside.

And if you insulate/seal the garage too well, then w/o a return or any place for air to escape, you will not get much airflow out of your garage supply vent.

Assuming I can determine which is which, would it likely be a duct within a duct? If so, is there a special type vent I would need to accomplish this?
You mean which is the supply vs. the return? Either way, both should just be a plain duct, likely insulated, but not double walled (duct within a duct).

If you're absolutely set on this idea, then you should find a louvered vent cover that can fully seal when closed (so that when you're not in the garage and you close the vent then your system is back to normal), and that does not protrude into the main trunk and block airflow.

I hate to say it, but you're probably best off installing a heater specifically for the garage, e.g.:



It may actually save you money in the long run..
 

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Seems like running it that way is likely to depressurize your house and pressurize your garage so your house will likely draw in whatever your working on in the garage anyway.
 

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Discussion Starter #4
Thanks!

Thanks ScottR & jogr,
I guess I'll start looking at other AC options. There are some affordable portable ac/heaters that might be a good solution.

Peace,
Mark
 
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