Combustion air vent (from garage)

[Rich Sumen]

Need some help on this one....
A single family, slab house. There is a "utility room" off the garage with a low effieicncy furnace and standard, 12 year old HWT. (not raised, on the floor)
This room is off the garage with a metal, exterior grade door to it (from garage). (note: there is an outside wall present in this room, and an attic above)

I observed one large "combustion air vent", (cut into the door) to this room, about 4" off the floor. My questions.....
I think it is OK to draw air from a garage ( yes / no?), but since this vent is only 4" off the floor, it could pull in garage gasses. Since "ignition sources" in garages, are required to be off the floor 18", should the "combustion vent", (if allowed) from the garage, also be required to be min 18" off the floor?

Thanks, in advance for your comments.

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[Rod Butler]

Nope, nada, no way.

You are correct the appliances need to be 18" off of floor if pulling combustion air from the garage.

[Rich Sumen]

Thanks Rod, But if the vents are raised, at the top of the wall or door, would that be OK? The furnace and HWT are in a seperated room?

[Robert Ernst]

Beyond the vent question is does this utility room have the proper fire separation since it's connected to the garage by the vents? I would suggest that the WH be elevated or replace with a FVIR type one. If you were to seal the door and put the vents above the 18" it wouldn't meet the requirements of the vent being with in 12" of the bottom.

[Rich Sumen]

Yes,
The room is fire rated.
I guess the answer is either raise the appliances, or install
combustion intake vents to the exterior or attic.

[Jerry Peck]

Need some help on this one....
A single family, slab house. There is a "utility room" off the garage with a low effieicncy furnace and standard, 12 year old HWT. (not raised, on the floor)
This room is off the garage with a metal, exterior grade door to it (from garage). (note: there is an outside wall present in this room, and an attic above)

I observed one large "combustion air vent", (cut into the door) to this room, about 4" off the floor. My questions.....

- "I think it is OK to draw air from a garage ( yes / no?),"
- - Yes.
- "but since this vent is only 4" off the floor, it could pull in garage gasses."
- - Correct.
- "Since "ignition sources" in garages, are required to be off the floor 18","
- - Correct.
- "should the "combustion vent", (if allowed) from the garage, also be required to be min 18" off the floor?"
- - No, not required.

The room is fire rated.

- Typically, no, the room is not "fire rated". That room should be "separated" from the garage by at least 1/2" gypsum board and all openings through the walls of that closet which back up to the house walls need to be sealed and any penetrations through or into the wall sealed around.
- Any openings through the ceiling also need to be sealed and any penetrations through the ceiling need to be sealed around.

I guess the answer is either raise the appliances, or install
combustion intake vents to the exterior or attic.

"I guess the answer is either raise the appliances"

Nope, the answer is to raise the appliance *and* ... do any of the other things which are necessary. With that door opening to the garage, that closet is considered to be 'part of the garage' just as though the water heater were setting out in the garage.

You would need to address the combustion air in accordance with combustion air requirements.

[Rich Sumen]

Jerry,
I'm a bit confused.
If the vent can be that low (makes sense now), and the room is just treated
as "another part of the garage", then the answer would be "have the ignition sources" higher than 18".
That has to be ok.

Yes?

[Bob Harper]

G2408.2.1 does not allow combustion air to be drawn from a garage.
R302.5 requires all penetrations to a garage be sealed with a 1 3/8" solid wood door, 1 3/8" metal door or 20 min. fire rated door. That precludes passive openings
R302.6 sets the required separation from the habitable portion of the house, which calls for 1/2" drywall. A hole in the drywall violates this requirement.

A passive hole in the wall below the 18" vertical separation brings that closet effectively into the garage and therefore would require either jacking it up on a 18" stand or replace it with a gas FVIR or electric WH.

Also, ASHRAE does not allow you do draw combustion air from sources where combustible fumes can be expected.

The mfr. would also probably have a prohibition from drawing combustion air from a garage less than 18" from the floor.

Q- is the wall separating this closet from the garage insulated with interior wall sheathing or is it just one sheet of drywall facing the garage?

[Rich Sumen]

Thank everyone.
Jerry is right. There is no issue with the "room off the garage" housing
the appliances, whether there is a door between them or not. This room,
"with a wall or door vent" into the furnace room, makes it "just part of the garage" as Jerry stated, and as such, can have a furnace and / or hot water tank.
The wall and ceiling of the room does need " proper fire separation", and they are proper.
I guess the only real confusing thing, is why the builder would not just have installed a solid door (no vent) to the furnace room, and then provide combustion air from the exterior or attic. (in this small furnace room)

Oh well, You just never know what they were thinking.

Thanks for everyones help!

[Jerry Peck]

G2408.2.1 does not allow combustion air to be drawn from a garage.

Bob,

Where does it state that?

2012 IRC
- G2408.2.1 (305.3.1) Installation in residential garages.
- - In residential garages where appliances are installed in a separate, enclosed space having access only from outside of the garage, such appliances shall be permitted to be installed at floor level, provided that the required combustion air is taken from the exterior of the garage.

All that says if that the appliance is installed on the floor ... then ... the required combustion air is not allowed to be taken from the garage.

However, if that water heater is raised as has been suggested and recommended, then the required combustion air can be taken from the garage.

Another side point for discussion: "provided that the required combustion air is taken from the exterior of the garage"

I will start off by stating that other codes which specifically state "required" are not addressing 'non-required' items/areas/etc.

An example is that a door may no swing into "required" egress width greater than 50% during its swing, however, if the egress path (such as a corridor) is wider than "required" for the number of occupants, then only the "required" width is prohibited from having the door swing into it more than 50% of that "required" width.

Nit picking you say? Nope, that specificity is done all the time.

Now, back to the "required" combustion air - can "additional" 'non-required' combustion air be taken from the garage?

R302.5 requires all penetrations to a garage be sealed with a 1 3/8" solid wood door, 1 3/8" metal door or 20 min. fire rated door. That precludes passive openings

That's not what that section says either:
- R302.5 Dwelling/garage opening/penetration protection.
- - Openings and penetrations through the walls or ceilings separating the dwelling from the garage shall be in accordance with Sections R302.5.1 through R302.5.3.

- R302.5.1 Opening protection.
- - Openings from a private garage directly into a room used for sleeping purposes shall not be permitted. Other openings between the garage and residence shall be equipped with solid wood doors not less than 13/8 inches (35 mm) in thickness, solid or honeycomb-core steel doors not less than 13/8 inches (35 mm) thick, or 20-minute fire-rated doors, equipped with a self-closing device.

- R302.5.3 Other penetrations.
- - Penetrations through the separation required in Section R302.6 shall be protected as required by Section R302.11, Item 4.

The passive vent is not between the garage and the residence:
- G2408.2 (305.3) Elevation of ignition source.
- - Equipment and appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in hazardous locations and public garages, private garages, repair garages, motor fuel-dispensing facilities and parking garages. For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate directly with a private garage through openings shall be considered to be part of the private garage.

Exception: Elevation of the ignition source is not required for appliances that are listed as flammable vapor ignition resistant.

R302.6 sets the required separation from the habitable portion of the house, which calls for 1/2" drywall. A hole in the drywall violates this requirement.

What hole?

The passive vent hole? That is not in the separation wall because the separation wall is going around the sides and back of that closet (space).

A passive hole in the wall below the 18" vertical separation brings that closet effectively into the garage and therefore would require either jacking it up on a 18" stand or replace it with a gas FVIR or electric WH.

Correct, that is what we are saying: raise the water heater 18" above the floor.

Q- is the wall separating this closet from the garage insulated with interior wall sheathing or is it just one sheet of drywall facing the garage?

That is the question, and if the closet has 1/2" gypsum board around the inside of the closet, then the closet is part of the garage.

There are limitations placed on that closet and the water heater in that closet if one tries to consider that closet as 'not part of the garage'.

I realize this post is a bit long and that I specified various things, but that might be why your code sections were incorrect - you didn't specify the specific things which may make those correct references on a specific set of conditions.

I prefer the simplicity of the older editions: if the closet opens only to the garage (and not to the habitable space too), then the closet is part of the garage ... no ifs, no ands, no buts.

[Jerry McCarthy]

Think Bob was referring to "return air," not combustion air?

On another topic I think eliminating suicide vents in garages was a big mistake.

[Bob Harper]

The way I read it made it sound like the closet was constructed as part of the living space with connection to the garage. If it is separate and essentially part of the garage then yes, in one sense, it can be there. More on that in a minute.

Jerry, if you weren't in such as hurry to jump on me you'd see where I made the same point about it being ok to put the WH in there at 18", FVIR on the floor or electric.

I asked about the wall to the garage being insulated and weatherized or not but should have clarified if this space was conditioned or not. What I was after was if the venting was B-vent all the way or was there single walled vent connector in an unconditioned space, which a garage would be.

Sorry but your 'required' analogy does not make sense to me. Try again.

The issue of makeup air is still unclear with the input BTU ratings and room volume.

Another issue is that of duct sealing. Being in direct communication with a garage makes it vitally important not only for the ducts to be properly sealed.

Final point: since home inspections are not 'code inspections', you are allowed in most states to call out things of a practical nature not reflected yet in the codes. For instance, while acceptable to draw combustion and makeup air from the garage under the limitations noted, it is a bad idea if certain chemicals and aerosols can be expected to be present in the garage as they may exhibit a corrosive effect on the appliances. I've seen where the concrete floor in a garage was washed with muriatic acid then a gas direct vent fireplace installed in there 6 months later and it literally ate that fireplace up. Picking fly poop out of black pepper is one thing but at some point you also have to look at the practical side of it. If you see something you feel in your experience may likely cause a problem you'd better call it, if nothing else for someone else to take a look and make it their problem. Putting HVAC equipment outside the thermal envelope of a house, even if it meets code is still stupid.

[Jerry Peck]

The way I read it made it sound like the closet was constructed as part of the living space with connection to the garage. If it is separate and essentially part of the garage then yes, in one sense, it can be there. More on that in a minute.

I read it as it was a closet/space off the garage with a door to the garage and not to the house "There is a "utility room" off the garage", and, yes, that leaves the question open as to whether the inside is finished off or not - but - I thought he addressed that with "Yes, The room is fire rated." ... maybe he did not address that, but that is how I read the room is fire rated.

Jerry, if you weren't in such as hurry to jump on me

Bob,

Not in a hurry to jump on you at all, it was just that your statements and references did not entirely reflect what was/would be needed for those to apply.

Which is why I made my comments more specific - to clarify what I was saying and referring to, and that was also why I said "you didn't specify the specific things which may make those correct references on a specific set of conditions."

[Rod Butler]

[quote=Bob Harper;191153] . . .

Also, ASHRAE does not allow you do draw combustion air from sources where combustible fumes can be expected.
. . . .quote]

Bob, not sure where you saw this in the ASHRAE guides but I can see no such requirement in any of my ASHRAE books.
But this is not really an ASHRAE issue.

Code issue and equipment manufacturer's requirements for sure.

[Jerry Peck]

. . .

Also, ASHRAE does not allow you do draw combustion air from sources where combustible fumes can be expected.
. . . .

Bob, not sure where you saw this in the ASHRAE guides but I can see no such requirement in any of my ASHRAE books.
But this is not really and ASHRAE issue.

Code issue and equipment manufacturer's requirements for sure.

Huh?

You mean a regular water heater, raised 18" above the garage floor, drawing combustion air from the garage, is no longer allowed in the garage at all?

Where is that stated?

[Rod Butler]

[quote=Jerry Peck;191826]

Huh?

You mean a regular water heater, raised 18" above the garage floor, drawing combustion air from the garage, is no longer allowed in the garage at all?

Where is that stated?

Jerry I'm not sure you understood my post, I certainly don't understand yours.



No where did I say that a water heater could not be installed in a garage, I simply stated that I could find no guidelines in the ASHRAE handbooks that restricts using combustion air from a garage for said water heater.

I think we are talking zebras and tomatoes here.

[Jerry Peck]

Jerry I'm not sure you understood my post, I certainly don't understand yours.



I think we are talking zebras and tomatoes here.

I fixed the broken quote in my quote of your post - does that help?

Added with edit: DANG! I fixed the broken quote and it broke again - it was correct when I viewed it after posting it.

I see your post has a broken quote too - must be something going on with the software for Brian's forum, probably a no-longer-recognized or supported command ... I hate it when that happens, I spent half the weekend fixing similar things in mine, and I still have some to find yet. They even have a term for those things: "Deprecated" which simply means you have out-of-date-software-and-if-you-don't-upgrade-your-software-it-will-stop-working-properly.

[Rod Butler]

[quote=Jerry Peck;191843]

I fixed the broken quote in my quote of your post - does that help?

Ah, yes we are communicating.