exterior air for fireplaces

[Jim Baird]

IRC 2000 Section R1005 requires exterior air supply for factory built and masonry fireplaces.

It goes further (R1005.2) to prohibit source of air from garage or basement, and from elevation higher than firebox.

A local contractor has been vociferous in protest of a denial of his air intake that terminates in a soffit outside the chimney.

He claims his letter from the manufacturer(Heatilator), that states, "it is often times necessary to run the outside air duct vertically...in close proximity of the termination cap of the fireplace..." amounts to manufacturer's instructions (which R1005.1.1 allows).

Our office consensus says that such "instructions" should be issued by way of printed materials included with every unit sold.

Have there been similar discussions in other places?

[Paul MacLean]

For a long time I wrote up fireplace air vents that are higher than the firebox for the same reasons Jim mentioned. Down here I frequently see them vented through the side of the chase above the roof when the fireplace is on an interior wall and you can't easily run the vent directly outside.

Then I finally found manufacturer's instructions that said it was OK to run the vent above the roof. Since then I quit hassling everyone and don't mention it anymore. Unless it's early in new construction, it's something that isn't going to get changed anyway.