Thread: Supply registers in attached garages.

I've been seeing HVAC supply registers lately that are installed to bring heat and/or A/C into attached and integral garages. This seems like it is probably a breach of the fire resistant barrier, but they are mounted on metal ductwork, so is this a breach of the fire resistant barrier or not?

At least I haven't seen a return register in a garage yet. That would really distribute exhaust fumes and smoke from a fire throughout a home pretty quickly. Some bright home owner will probably figure out that if you're going to supply, then you should probably return as well, and go ahead and install one, and I won't be too surprised when I see it.

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not allowed!! that's why you see electric or hot water fan heaters in garages.

Originally Posted by Michael Chambers

I've been seeing HVAC supply registers lately that are installed to bring heat and/or A/C into attached and integral garages. This seems like it is probably a breach of the fire resistant barrier, but they are mounted on metal ductwork, so is this a breach of the fire resistant barrier or not?

To expand on what Wayne said ... not allowed to have supply or return from the living space which open to the garage.

One does not want the garage air and fumes (CO, paint, gasoline, fertilizer, or any of the other items people keep in their garages) going into the duct work and into the living space.

Breaching the separation wall is just a minor issue, killing them with CO would be a bigger issue (because it would be more likely to happen).

Now, if the supply vents, and return vents, were to/from a system which served the garage only (does not mix air with the living space air), then that would be allowed.

Originally Posted by Jerry Peck

To expand on what Wayne said ... not allowed to have supply or return from the living space which open to the garage.

One does not want the garage air and fumes (CO, paint, gasoline, fertilizer, or any of the other items people keep in their garages) going into the duct work and into the living space.

Breaching the separation wall is just a minor issue, killing them with CO would be a bigger issue (because it would be more likely to happen).

Now, if the supply vents, and return vents, were to/from a system which served the garage only (does not mix air with the living space air), then that would be allowed.

Thanks Jerry, but just to clarify, I'm talking supply registers only, with no returns being installed. It's not very efficient as far as HVAC systems are concerned, but at least I'm not seeing where any of the garage air is deliberately being brought back into the system and the rest of the house.

Originally Posted by Michael Chambers

Thanks Jerry, but just to clarify, I'm talking supply registers only, with no returns being installed.

Still opens the ductwork for the living space to the garage.

What happens in that ductwork when the system is off and the fan is not running? Air will exchange between the garage and the living space through the open ductwork (the open supplies in the garage and in the living space).

It's not very efficient as far as HVAC systems are concerned, but at least I'm not seeing where any of the garage air is deliberately being brought back into the system and the rest of the house.

The supplies may not be "deliberately" used to bring air back into the system and the rest of the house, but the supplies are doing that anyway ... "deliberately" or unintentionally.

Regarding the separation wall - the ductwork penetrating into the garage from the living space or its attic needs to be 26 gauge metal or fiberglass duct, not flexible duct, and the fiberglass duct needs to be protected from physical damage ... neither is allowed to have any openings to the garage.

I think this was covered in a thread several weeks back.

I did not know fibreglass ducts were fire rated.
Link please.

Originally Posted by Jerry Peck

Still opens the ductwork for the living space to the garage.

What happens in that ductwork when the system is off and the fan is not running? Air will exchange between the garage and the living space through the open ductwork (the open supplies in the garage and in the living space).

No disagreement there. That's why I didn't like what I was seeing.

Originally Posted by Jerry Peck

............. the ductwork penetrating into the garage from the living space or its attic needs to be 26 gauge metal or fiberglass duct, not flexible duct, and the fiberglass duct needs to be protected from physical damage ... neither is allowed to have any openings to the garage.

Couple of points of confusion on my part here. (Bold was added.) How can any ductwork be "legally" penetrating into the garage if it is not allowed to have any openings to the garage? Also, the binder in most fiberglass that I'm familiar with is fairly flammable. How can that be the safe equivalent to 26 gauge metal? Thanks a lot!

Originally Posted by Michael Chambers

How can any ductwork be "legally" penetrating into the garage if it is not allowed to have any openings to the garage?

I do not mean to answer a question you have for Jerry, Micheal but ducts service appliances.
It is acceptable when done correctly.
R309.1.1 Duct Penetration. Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be constructed of a minimum No. 26 gage (0.48 mm) sheet steel or other approved material and shall have no openings into the garage.

If homes were built, maintained, renovated or restored correctly, methinks we would be looking for another revenue stream and I would certainly miss the codified knowledge, professional camaraderie, and distinguished friends I have come to know and admire on Brian Hannigan's InspectioNews. Does someone have a hanky I could borrow? My Lacrimal gland is activating just at the thought of it.
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From the IRC: (underlining is mine)
- SECTION M1601 DUCT CONSTRUCTION
- - M1601.4 Installation.
- - - Duct installation shall comply with Sections M1601.4.1 through M1601.4.7.
- - - M1601.4.8 Ducts located in garages.
- - - - Ducts in garages shall comply with the requirements of Section R302.5.2.


- R302.5.2 Duct penetration.
- - Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be constructed of a minimum No. 26 gage (0.48 mm) sheet steel or other approved material and shall have no openings into the garage.

- APPROVED. Acceptable to the building official.

- R104.9 Approved materials and equipment. - - Materials, equipment and devices approved by the building official shall be constructed and installed in accordance with such approval.
- R104.11 Alternative materials, design and methods of construction and equipment.
- - The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code. Compliance with the specific performance-based provisions of the International Codes in lieu of specific requirements of this code shall also be permitted as an alternate.

All AHJ I am aware of also allow minimum 1 inch fiberglass ductboard ducts in the garages, the building official is the one who "approves" alternatives, and the building official "shall" approved the alternative items when the building official "finds" (or has been shown by others) that the material blah, blah, blah ...

Now, would fiberglass duct be allowed to penetrate a rated wall? Nope. But the walls and ceiling separating garages from living space are not fire walls, are not rated walls, they are simply "separation" walls ... and only require 1/2" gypsum board on the garage side - not even Type X gypsum board, just regular drywall. That is, unless your specific location has amended the code to require true fire-resistance rated walls and ceilings between garage and living space.

Originally Posted by ROBERT YOUNG

I do not mean to answer a question you have for Jerry, Micheal but ducts service appliances.
It is acceptable when done correctly.
R309.1.1 Duct Penetration. Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be constructed of a minimum No. 26 gage (0.48 mm) sheet steel or other approved material and shall have no openings into the garage.
.

Thanks Robert! I don't mind who answers the question, as long as it gets answered. The actual code wording you provided makes it understandable. Yea, we do see ductwork penetrating into and through garage areas all the time, without having any registers installed that are open into the garage. There's no potential for air exchange as long as the penetrations are well sealed.