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Discussion Starter · #1 ·
We're in the process of reconfiguring our garage, and knocking it out of the 1970s. That includes:

  • removing all the godawful paneling
  • adding insulation to the exterior walls
  • adding some additional outlets/circuits
  • finishing out with drywall (using fire-rated Type-X between the garage and living space)
  • enclosing a laundry room (which brings us to this post)
We've got a gas water heater with an atmospheric vent. Before we get into potentially ugly corners, I just wanted to tap the hive mind on a few things.


1) Combustion Air. Since we're walling off the laundry space, that's constraining the replenishing air supply. The floor is being raised about 14" to bring things level with the rest of the house, which give us an opportunity. We're moving the dryer (and putting in a new vent), and it occurs to me that I could use the old 4" exhaust vent that cuts through the exterior wall as an alternative supply. I'm thinking of attaching the exhaust pipe to a floor vent in the raised platform. Any red flags with this I'm not seeing?


2) Water Lines. Since everything is being lifted, it's an opportunity to relocate the water lines connected to the hot water heater. Right now, the water lines come in about floor level, and use copper to travel up above the water heater. Any codes I should be aware of. Planning on using standard PEX approaches, and have the fittings coming out of the wall.



3) Gas Line. With the floor being raised, the gas line needs to be adjusted since the cutoff valve would wind up beneath the raised floor. Since I'm going to that trouble, it makes sense to look further down the road when we eventually shift to a tankless water heater. We currently have a 3/4" line coming in. Will that be sufficient? Related: Is there a "standard" connection layout for water and gas that I can go ahead and move everything to?


4) Last curiosity. Is it possible to convert an atmospheric vent gas water heater to a direct vent one? Maybe with concentric venting that runs out the ceiling?
 

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You sound very ambitious.
Gas water heater vent: learn your local code, but basically, if you have it going horizontally (with 1/4" slope per foot), this portion must be less than 75% of the vertical portion.
I don't know your existing dryer vent, so I can't comment on your plan.
BTW, enclosing a WH, you'll still have plenty of fresh air. Some folks have gas WHs in closets with no problems.
About the main gas supply, you need it larger than 3/4" for a tankless WH.
 

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Your water heater will be competing for replacement air with the dryer so combustion air concerns are valid.
"I'm thinking of attaching the exhaust pipe to a floor vent in the raised platform."
Both dryer and water heater exhaust need to be vented to the outside, not to the garage.

The new space will now need to receive the same drywall and fire door protection from the garage.

Between the electrical, gas, and construction you should be pulling permits. Better now than down the road and doing so now will make sure all is up to code.

Note, my insurance company pulled a random policy inspection to be sure things had remained the same over the years and they specifically questioned any construction (PITA). And permits were questioned.

I suspect municipalities would or maybe are doing the same for tax purposes.

Bud
 

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There are a bunch of variables in play here. Are you creating a laundry room you access from inside the house? Or is it still a closet accessed from the garage? Is there a door? Will the combustion air pipes be horizontal or vertical? Are you going to use indoor, outdoor, or combined for combustion air?

These variables will get you started down a path to figure your combustion air required. It is based on the BTU input rating of those appliances. Things like a minimum size of space, if open to garage, minimum heights (18" above floor). Minimum size of air openings, number of openings (like one high, one low).

Follow the recipe in International Mechanical Code Chapter 7/International Residential Code Chapter 24.
 

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Discussion Starter · #6 ·
Your water heater will be competing for replacement air with the dryer so combustion air concerns are valid.
"I'm thinking of attaching the exhaust pipe to a floor vent in the raised platform."
Both dryer and water heater exhaust need to be vented to the outside, not to the garage.
Exactly. The (electric) dryer currently vents to the outside via a passthrough. I am intending to install a new vent for the dryer compatible with the raised height. The old passthrough vent, then, becomes available for an intake for combustion air for the hot water heater.

The new space will now need to receive the same drywall and fire door protection from the garage.
Yep, using 5/8" Type-X fire rated drywall, and planning a solid core door (but need to double check the fire rating). Typically enough for the house, the garage was originally clad in only bad paneling, and the door was originally only held in by the trim, so we're definitely upgrading :)


Between the electrical, gas, and construction you should be pulling permits. Better now than down the road and doing so now will make sure all is up to code.

Professionals and permits are involved where appropriate, I'm mainly asking for first impressions from you guys and semi-anonymously shedding my "stupid" questions early :)

Thanks!
 

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Discussion Starter · #7 ·
There are a bunch of variables in play here. Are you creating a laundry room you access from inside the house? Or is it still a closet accessed from the garage? Is there a door? Will the combustion air pipes be horizontal or vertical? Are you going to use indoor, outdoor, or combined for combustion air?
Accessing the laundry room from both, effectively becoming a mudroom of sorts. Ensuring that fire protection is upgraded on the garage side, and looking to replace the intake air to ensure safe combustion.


The combustion air would draw in horizontally and low via a repurposed dryer exhaust vent (as the dryer is being moved), go through a 90-degree bend and enter through the floor. The exhaust pipe is solely vertical.


Combustion air would effectively be a combination, using the room space, replenished primarily from the outside (but I can't rule out it might also draw from the kitchen - definitely not from living spaces, through)


Follow the recipe in International Mechanical Code Chapter 7/International Residential Code Chapter 24.
Looked at that a while back to confirm the new space was undersized (which is why I started thinking about replacement air). Any suggestions for verifying a 4" dryer exhaust vent can handle the necessary airflow?

Thanks!
 

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Looked at that a while back to confirm the new space was undersized (which is why I started thinking about replacement air). Any suggestions for verifying a 4" dryer exhaust vent can handle the necessary airflow?
It sounds like you can follow the code yourself line by line, as I don't know the parameters of your room and doors and such. But for a 35,000btu water heater @50cuft/1000btu, that's 1750cuft volume you need in the room. If you have that, you don't need the outside air. You can also combine rooms, be careful of a kitchen with exhaust hood though, as long as you have no doors or put pass-throughs.

The 4" old dryer vent is ~12sqin, you need a different cap, and there might be a reduction in net free area depending on that cap. If you needed outside air, that probably won't do it, and might be covered behind the dryer anyway.

The top combustion air I was talking about is a high/low combination if you go that route, wasn't talking about the vent for the natural exhausting of CO.
 

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Discussion Starter · #9 · (Edited)
It sounds like you can follow the code yourself line by line, as I don't know the parameters of your room and doors and such. But for a 35,000btu water heater @50cuft/1000btu, that's 1750cuft volume you need in the room. If you have that, you don't need the outside air. You can also combine rooms, be careful of a kitchen with exhaust hood though, as long as you have no doors or put pass-throughs.
  • The water heater is a Lochinvar LTN050G, so 40,000btu needing 2000cuft. The room will wind up 11.25'x7.5'x8', so it comes in short at 675 cuft.
  • We're planning a pocket door to the kitchen (itself part of a large open floor plan about 26'x26'x8' (~5400cuft). Center of the door will be approximately 8' from the stove/hood
  • The floor will be raised about 14" to match the kitchen level, so the old dryer vent will be underneath the floor, and can be rerouted anywhere we want
  • A fire-rated door will go to the garage, so let's discount any contribution there.
I haven't included the kitchen because the pocket door would normally be closed. Am I overlooking a great benefit?
 
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