Product Brochure

13
Summary
We have seen a growth in the use of products like stucco, fiber cement and brick—moisture-retaining claddings that increase the
moisture load on the wall. Exterior continuous insulation is (increasingly being used) on the exterior sides of walls to meet the growing
demand for energy-efcient wall assemblies; however, these designs are affecting the way that moisture gets in and out of your
buildings. Today, there is more moisture in our homes than ever before and new construction practices are only trapping the
moisture in the wall longer, making its risk of moisture-related failure much greater. Building practices have increased the R-value
while reducing the air movement through the wall. The result is a wall with a much lower rate of drying. Once the wall gets
wet — and it will! — it stays wet.
MemBrain is an ideal air barrier and moisture management solution for the unique challenges of “mixed-humid” and “cold” climate
condition areas in North America. As a certified interior air barrier, it helps create a tighter building envelope to achieve optimal energy
efficiency, indoor air quality (IAQ), homeowner comfort and moisture management. And unlike traditional vapor retarders, MemBrain’s
unique adapting permeability supports an airtight shell that can still maximize drying potential, helping maintain a healthy home
throughout seasonal climactic changes.

visit www.certainteed.com/buildingscience

by increasing the construction’s tolerance to moisture load. It is appropriate in cold and mixed climates, but it is
not suited for hot climates with high outdoor humidity because it would always be under high, relative humidity
conditions. Therefore, it would always be permeable and would not provide vapor retarding benefits. It also would
not work well in buildings with exceptionally high, constant indoor humidity levels, such as swimming pools and spas.
However, in rooms with short peaks of high humidity (bathrooms and kitchens), MemBrain’s performance would not
be affected due to the buffering action of interior finishes.
MemBrain’s molecular structure changes and reduces vapor permeance ~1 perm during the winter, preventing indoor
moisture from penetrating into the cavity.
During the summer, MemBrain’s vapor permeance adapts to ~20 perm, so that moist outdoor air penetrating the
structure can now escape to the indoors, helping prevent building damage.
MemBrain can adapt from <1 to 35 perm to keep
moisture out of the cavity in the winter while letting it
escape when cavity humidity increases in the summer.
MemBrain Delivers Proven Barrier Technology

decade of usage and performance data worldwide

ASTM E84, for flame spread


MemBrain can adapt from fully closed to open
(<1 to 35 perms) to provide greater drying capability.
40
35
30
25
20
15
10
5
0
0 10 20 30 40 50 60 70 80 90 100
WALL CAVITY HUMIDITY (%)
ASTM 96
WATER VAPOR PERMEANCE (perms)
MemBrain Asphalt-coated Kraft 4 Mil Polyethylene