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Title: Field Testing of an Unvented Roof with Fibrous Insulation, Tiles, and Vapor Diffusion Venting

This research is a test implementation of an unvented tile roof assembly in a hot-humid climate (Orlando, FL; Zone 2A), insulated with air permeable insulation (netted and blown fiberglass). Given the localized moisture accumulation and failures seen in previous unvented roof field work, it was theorized that a 'diffusion vent' (water vapor open, but air barrier 'closed') at the highest points in the roof assembly might allow for the wintertime release of moisture, to safe levels. The 'diffusion vent' is an open slot at the ridge and hips, covered with a water-resistant but vapor open (500+ perm) air barrier membrane. As a control comparison, one portion of the roof was constructed as a typical unvented roof (self-adhered membrane at ridge). The data collected to date indicate that the diffusion vent roof shows greater moisture safety than the conventional, unvented roof design.
 [1] ;  [1]
  1. Building Science Corporation, Westford, MA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Resource Type:
Technical Report
Research Org:
Building Science Corporation, Westford, MA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B) (Building America)
Country of Publication:
United States
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION residential; residential buildings; BSC; Building Science Corporation; Building America; unvented roof; cathedralized roof; hot-humid; tile roof; diffusion vent; moisture risks; moisture damage