Thread: Return air duct passing through firewall

Isn't this return air duct a breach of firewall integrity? Could a modification be made that would make this firewall acceptable?

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First, are you sure that is a firewall?

What is on each side of it?

Second, are you sure that is a return air duct, that looks more like an air connector. Unlike air duct, air connectors are limited in length to 14 feet.

This is a firewall. A kitchen and living room are on the opposite side of the wall. The furnace is in the garage. This vent passes through the firewall into the attic, then terminates at the register in the hall. The supply ducts run through the crawlspace.

What is the function of an air connector?

Originally Posted by Ron Bishop

This is a firewall. A kitchen and living room are on the opposite side of the wall. The furnace is in the garage. This vent passes through the firewall into the attic, then terminates at the register in the hall. The supply ducts run through the crawlspace.

You SURE it is a "firewall"?

Does California require a "firewall" between the garage and the living space? If so, what fire-rating? 30 minutes? 1 hour? 2 hour? And the door is REQUIRED TO BE A FIRE RESISTANCE RATED DOOR listed and labeled for at least 20 minutes, automatic closers, installed with fire-resistance rated jambs, etc.?

Or is it a "separation wall".

That said ... and regardless which it is (but it makes a difference as to what would be "correct") ... that installation is incorrect.

An "air duct" is insulated and an "air connector" is ... well, basically the inner duct of the air duct without the insulation or outer covering.

Typically the only place you would find an "air connector" would be in a commercial installation where the ceiling plenum was return air, but some specific returns were installed for specific reasons, the air inside the air connector and the air outside the air connector would be the same temperature and thus there would not need to be any insulation - that was basically as explained to me when I talked to the engineer at the Air Diffusion Council a number of years ago ... because I had never seen an air connector and was wanting to know what one was, and I still have not seen an air connector (to my recollection). When an air connector is needed, typically they just install a length of air duct, because they have it on the job already, and air duct has not length limitation.

Making two separate not-as-long post of it.

If that is a separation wall, the duct on the garage side would need to be 26 gage minimum on the garage side and where it penetrates through the wall. The other side can be anything it wants.

If that is a firewall, not only would the duct on the garage side need to also be 26 gage minimum, but there would need to be a fire damper where that penetrates through the wall, it would all need to be properly fire caulked in accordance with a UL fire-resistance rated penetration, most likely with angles around that duct, fire paddies or caulking or special angles which have it built in, etc.

As soon as something becomes a "firewall" EVERYTHING changes and must be installed just right in accordance with a UL listed penetration design number.

If you call it a firewall and it is not, and someone believes you, and a fire goes through that wall, a good attorney will have you and all your assets for by lunchtime and by dinner would have divided your assets up between them and their client - that is one reason I keep pointing out the improper use of "firewall" (improperly used here 99.99% of the time).