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How to properly ventilate a garage turned into a play room?

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I live in Northwest Florida.  Currently I have a double garage and at the back of the garage is a partially boxed in area (3 full sides and partial sides where the opening is) that has a washer, dryer, and natural gas water heater.  The heater sits on a "stand" that supports it about 2 feet off the ground.  I don't currently see any air vents except the exhaust vent.  I assume this is all correctly done so far.

My plan is to build a dividing wall that will cut my garage in 1/2 parallel to the garage door.  So I will end up with a short garage in the front of the house and a game/play room in the back part of the house.  There is a door to the outside in the back as well as a door that leads into the house.  I sort of have 2 related questions.

1.  What is the best way to heat/cool this area?  I was planning on tapping into the HVAC system and running a vent into the middle or near middle of the room (all in the attic).

2.  Will new ventilation and/or sealing off the front half of the garage (as well as installing a threshold at the back door that it currently does not have) have a negative effect on the water heater ventilation?

Thanks for any input you can give me!!!
asked in Heating System by chavisc (120 points)
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1 Answer

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Hi Chavisc,
Unless there are specific local laws that would prevent you from doing what you are describing, like transforming part of your garage into a living space / play room, the following are my answers smiley:
This would be an answer to your second question: 
If I understood correctly the water heater would end up being in a playroom area and since, as you’ve mentioned, there are no vents in your garage providing necessary combustion air for water heater. I’m assuming that this is not a direct type water heater that uses exterior air for the combustion process – it would have a special type of a double wall vent pipe (not a B-vent) or two pipes attached to it (one for exhaust and one for intake of air from exterior).
Since you’re cutting the garage air volume in half, you need to calculate the remaining space and determine if it will be sufficient for your water heater, all the details are in my post here: -
If, based on your calculations, there’s not enough air volume in that created playroom (or garage, if that’s where the WH ends up) to support clean combustion, you’ll need to provide additional sources of air. This can be from the exterior or from the adjoining house (except for a bedroom). However, suggesting your home as a combustion air source for the water heater is only under the assumption the new garage area will be properly sealed off / separated. Also, the new playroom cannot be used as a sleeping area. This is for two reasons:
  • you cannot have a not direct vent type gas burning water heater installed in a sleeping area
  • you cannot have a garage door opening into a sleeping area
Since you’re building a wall to separate garage from this new playroom area you’ll find necessary information about it here - http://checkthishouse.com/744/garage-fire-wall-separation-wall.html
Now the question concerning heating and cooling of your playroom area. If it’s not the garage section you can tap into the home’s system, just make sure that your provide intake and return. Otherwise there will be no air circulation and impossible to properly condition this new area. 
The only thing is that since you have a water heater in that playroom you cannot install a return vent if it ends up in a sleeping area of your home, it has to be open into some other section; an open hallway, living room, kitchen, etc., just like the combustion air supply.
Let me know if you have more questions, just click “comment” below.
answered by darekrudy (21,730 points)
First, Thank you for your answer.  I love your site btw.

I haven't looked at the links you provided yet, but I WILL.  My first GUESS is that it SHOULD have enough air volume.  The room will end up being aproximately 25' X(18' to 20') with the water heater in the center of the back wall but sourounded by 3 walls (as it is now) and next to the washer and dryer (this is where the opening is).

This room will not have anyone sleeping it it.  It will end up being 1/3 office, 1/3 exercise, 1/3 game/play room for my 10 and 11 year old boys (and friends).  The nice thing is the ceiling is already finished and my dad and brother installs carpet for a living (I have done it as well).  I should be able to get enough left over carpet from my dad and put that in myself.

Thanks again for your help!

UPDATE:  I took the measurements.  The BTU is 34,000 for that water heater and will mean it needs 1700 cubic feet.  The room will be 23' X 18' X 8' giving it 3312 cubic feet.  As far as that goes, it looks like I should be good to go.

That's good, less holes in the walls smiley, good luck with your project!

After reading through the links you provided, I have a question about the fire wall.  This is more concerning the way it is now since (as I see it) the new wall should aleviate the problem.  I have an attic stairs/door that once in the attic, I can get to pretty much the rest of the house.  The garage has what I believe to be proper drywall for a ceiling, but the door doesn't seem to have proper installation.  This would then be a fire hazard, correct?

So if I now plan to seal the garage portion (making it too small to even get a single car in but large enough  to have couple work benches) with a wall and there is no attic access (ceiling drywall is already there), this would be proper, correct?

One hopefully last question about the HVAC.  The garage is next to the kitchen area and living room area.  If I run the vent in the ceiling of the new room, should I just cut a whole in the wall between the new room and the kitchen/dinning area and install a vent there?  Or does this need to be something I can run through the ceiling itself.  One thing I failed to mention is the fact that I would like to have this process reversable in case it's not appealing to a future buyer down the road.  Also note that we have a doggy door installed in the door that now leads into the garage (the new office/game/exercise room).  Would taking the flap off (since the new room will be sealed) suffice?  I plan to add another doggy door to the back door of the (current) garage / new room.  Right now we just leave that door open when we are here so the dog can go in/out as he pleases.  I hope I didn't get too confusing this time.

Thanks again.  You have been a life saver (or at least a time saver).

You're welcome Chavisc smiley,


I’m not sure about the door (I believe you’re referring to the house entry…) because I don’t know anything about its installation. However, since you’re dividing the garage, this door will be now used for your new room access and it doesn’t have to be fire rated. If you are planning to put a new door in that dividing wall, it should comply with the garage firewall requirements.
As for the HVAC, you can put a return vent / opening in the kitchen / dining room wall. I don’t know how is your HVAC air duct system designed (single air return or individual air returns in each room) but ideally, a return port connected to the furnace return duct would provide best efficiency.
I think that covering a hole in the wall and removing single ceiling air supply port would be the easiest way in case this process needs to be reversed (one less duct to install and remove).
As for the doggy door… I don’t know if that would be fire rated, probably not. So in order to restore required firewall you’d have to replaced that section of the door with material that has the same rating as a fire rated door itself, or replace the entire door.
I’m glad I can help.

There won't be any doors going from the house/new room to the garage.  The only way in and out of garage will be using the big over-head door.  The doggy door is currently in the door that goes to the garage now, but this door will be used to access the new room.  Then there is a door that leads to the back yard that is currently part of the garage, but will be part of the new room once the change is made.  That door is the one I plan to add a second doggy door to allow the animals to go from outside to inside and still use the current doggy door to continue into dinning/living area.  From what I can tell, there is a single return in the center of the house where the furnace is.  This is where I would be replacing filters as well, correct?  So if this is the case, would removing the flap on the current doggy door (made for a large dog) that will be used for access to the new room suffice for a return?  I would just like to avoid that wall cut if possible.

I've attached a rough drawing (not to scale of course) to help visualize my project.


Everything is clear now smiley. Removing the door flap should do the job as an air return port and as your dog entry / exit point of course. The main return at the furnace would be the place to exchange air filters in this configuration.

Great!  Thanks again!!!!