HVAC outside air intake in a WUI zone

[Redmund]

Do outside air intakes for HVAC equipment in a Wildland Urban Interface zone require flame and ember resistant vents, or are these special vents only required at passive ventilation locations such as for an attic or crawlspace? The project is a commercial building, but the same question would apply to a residential building.

 

[arwat23]

2022 CBC Section 706A.1:
"Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical plane, shall be in accordance with Section 1202 and Sections 706A.1 through 706A.2 to resist building ignition from the intrusion of burning embers and flame through the ventilation openings."

Definition of "Ventilation" in CBC:
"The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space."


These are no different from other passive vents when it comes to WUI requirements. Comply with the ventilation opening requirements in CBC Ch 7A or the 2025 California Wildland-Urban Interface Code (if using 2025 codes).

 

[MtnArch]

I went round and round (4 comment lists) with a plan checker (who Can't Stinking Get it) who was DEMANDING we provide the ember-resistant eave vents (ie. Vulcan or Brandguard) at the intake and exhaust for a paint booth. She would *NOT* accept that 1) the equipment was all metal, 2) we offered to provide metal wire mesh with 1/4" spacing over each intake and exhaust, and 3) a 6"x14" ember resistant EAVE vent (as she suggested) would not cover a 30"x18" opening - and that the product most CERTAINLY wasn't tested for THAT configuration. I'm not sure the equipment would have functioned (and most likely would have burned itself up) by restricting the required openings with the ember resistant covers - even if they did make them in that size. We appealed to the CBO who also spoke to the FM about it, and they both shut her down that she was misinterpreting the code section and no cover (even the mesh) was required at those locations.

AND ...
This property was in an industrial area of *the city* (NOT rural) with one side of the street non-WUI and the other side WUI.

You can't make this stuff up, folks ...