Moisture Management

How MemBrain™ Works

Low Humidity. Diagram of moisture being blocked by moisture barrier while there is low humidity in the cavity.

Remains moisture tight in winter when humidity in the cavity is low

High Humidity. Diagram showing moisture exiting through walls during high humidity.

Increases permeability in summer to let moisture escape when needed

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MemBrain is unique among vapor retarders because of its ability to change its molecular structure. When humidity is low, it functions as a standard vapor retarder, like asphalt coated kraft paper. When humidity is high, it ranges from Class III (semi-permeable) to permeable. MemBrain is the only product on the market that straddles three vapor retarder categories.

Moisture Protection icon
Air Tightness icon
Class A Fire Rated icon

Continuous Air Barrier & Smart Vapor Retarder

CertainTeed’s exclusive MemBrain™ Continuous Air Barrier and Smart Vapor Retarder is the industry’s most advanced technology to create a better performing home.

This revolutionary solution can provide a continuous air barrier along with advanced moisture management and a Class A fire rating in a single product, helping achieve Complete Comfort. It’s another reason why choosing CertainTeed means you’re installing much more than trusted high-performance insulation products. You’re installing confidence.

Water Vapor Permeance

ASTM 96 Water Vapor Permeance to Wall Cavity Humidity line graph comparing MemBrain and Polyethylene performance
Line graph with one line representing MemBrain and one line representing Polyethylene. Y axis shows ASTM 96 water vapor permeance in perms. X axis shows wall cavity humidity in percentage. 4 mil of Polyethylene stays steady at 0.08 perms, while Membrain starts at 0.08 perms around 10-25% humidity, but as humidity percentage increases, MemBrain perms increase on a curve. At 100% humidity, Membrain perms are around 36. Anywhere from 10 perms and more is labeled “The drying zone.”

Why is MemBrain so smart?

Vapor Barrier
(Class I)
Vapor Retarder
(Class II)
(Class III)
Perm 0.01 to 0.1Perm 0.1 to 1Perm 1 to 10Perm 10 to 100
6 mil Polyethylene (0.05-0.06) MemBrain (0.8-36) Plain Gypsum Board (45-85)
It covers multiple classes for your protection. Table with vapor barrier classes.
Vapor Barrier (Class I): Perm 0.01 to 0.1 (6 mil Polyethylene falls in this class at 0.05-0.06). Vapor Retarder (Class II): Perm 0.1-1. Semi-Permeable (Class III): Perm 1-10. Permeable: Perm 10-100 (Plain Gypsum board falls in this class at 45-85). Membrain spans class II to permeable.