Uploaded May 2025 | Updated September 2026, 1 hour ago

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In this video we break down vapor diffusion ports, a strategy for managing moisture in unvented roof assemblies in warm climates (IECC zones 1-3) using a highly vapor permeable membrane at the roof ridge. Unlike traditional ridge vents, diffusion ports are airtight and watertight, while allowing vapor to escape without air infiltration. This method enables the use of fibrous insulation without exterior insulation or spray foam, reducing cost and complexity.

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*Vapor Diffusion Port Articles & Reports* :
BSI-088: Venting Vapor: buildingscience.com/documents/insights/bsi-088-venting-vapor

Moisture Performance of Unvented Attics With Vapor Diffusion Ports in Hot, Humid Climates (DOE): docs.nrel.gov/docs/fy24osti/86619.pdf

Field Testing Unvented Roofs with Asphalt Shingles in Cold and Hot Humid Climates: www1.eere.energy.gov/buildings/publications/pdfs/building_america/unvented-roofs-asphalt-shingles-cold-hothumid.pdf

Monitoring of Unvented Roofs with Diffusion Vents and Interior Vapor Control in a Cold Climate: energy.gov/eere/buildings/articles/monitoring-unvented-roofs-diffusion-vents-and-interior-vapor-control-cold?nrg_redirect=434355

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