Attic and crawlspace ventilation : implications for homes located in the urban-wildland interface

Abstract

Roof (attic and cathedral ceiling) and crawlspace ventilation has commonly been used as a moisture management tool to minimize performance problems associated with excessive moisture accumulation in these spaces. However, for homes located in the urban wildland interface, roof vents in particular provide an entry point into the attic for flame and burning embers. Research conducted at the University of California Fire Research Laboratory have shown that all forms of vents on the underside of the eaves (strip vents, frieze block, etc.), in both boxed and open-eave construction, are almost immediately penetrated under flame impingement exposures, confirming the vulnerability of vents to at least one kind of wildfire exposure. As a result of the observed vulnerability of vents to wildfire, they are sometimes eliminated, or relocated during construction, often without consideration for the potential effect on moisture control. Fortunately, alternative moisture control strategies have been suggested for moisture control and other performance related issues related to roofing. These strategies include alternative venting strategies, and minimizing heat, air, and moisture flow into attic and cathedral ceiling spaces by relying on construction details incorporated on the interior of the building. The objective of this paper is to review the function and vulnerability of vents, and examine alternative options.

Citation

Quarles, Stephen L.; TenWolde, Anton. 2004. Attic and crawlspace ventilation : implications for homes located in the urban-wildland interface. Proceedings from the Woodframe Housing Durability and Disaster Issues Conference : October 4-6, 2004 ... Las Vegas, Nevada, USA. Madison, WI : Forest Products Society, 2004: Pages 227-232.