Separation between garage and attic

[Frank Bombardiere]

I was telling a client that having holes in the garage ceiling was a breach of the separation between the garage and attic. He asked why then does the mechanical closet require the combustion air ducts that are open to the attic. I thought about it and did not have a good answer.

[Billy Stephens]

I was telling a client that having holes in the garage ceiling was a breach of the separation between the garage and attic. He asked why then does the mechanical closet require the combustion air ducts that are open to the attic. I thought about it and did not have a good answer.
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It's in an enclosed closet separate from the garage.
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[Frank Bombardiere]

True, but it is not sealed off from the garage. There is a door that can be left open and gaps around the door.

[Billy Stephens]

True, but it is not sealed off from the garage. There is a door that can be left open and gaps around the door.
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The door to the dwelling may be left open as well.
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[Jerry Peck]

If the door does not meet the requirements for the door between the house and the garage:
- R309.1 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.

And that includes being weatherstripped and with a threshold as that door would be the same as the door to the house - it would be in the thermal envelop of the living space.

If that door is not sealed and does not also meet the requirements for the door, then the 'garage' is considered to extend into the mechanical closet and the ceiling of the mechanical closet would be required, and any openings from the mechanical closet would not be allowed to terminate in the attic, those opening would be required to be extended out and through the roof, gable, etc.

[Frank Bombardiere]

I guess they don't enforce that here, because all the mechanical closets have doors with no weather strips and they are also hollow core wooden doors with sometimes a 2 or 3 inch gap under them. Yet they have the combustion air ducts from the closet into the attic.