Jan 12 2011
A new study by the NAHB Research Center comparing moisture resistance among typical residential exteriors evaluated brick veneer as the highest in moisture resistance and dryness.
As the trend toward lighter, tighter building methods continues to raise moisture concerns, the study aimed to determine how exterior cladding can impact the moisture content of the wooden components in the wall construction. Of the eight wall systems tested—accounting for approximately 90% of the cladding systems used today—brick veneer wall assemblies performed the best overall in controlling moisture.
“The lab report’s findings on brick’s superior moisture resistance are extremely significant,” notes J. Gregg Borchelt, President & CEO of the Brick Industry Association (BIA). BIA funded the study along with the U.S. Department of Agriculture’s Forest Products Laboratory and the U.S. Department of Housing and Urban Development. “Builders will want to choose brick if they wish to provide their customers the protection of a superior wall system—instead of one that is just ‘good enough.’”
Modern construction practices to increase comfort and energy efficiency have resulted in tight walls that are highly insulated and sealed against air filtration. When moisture is not sufficiently controlled, risks increase dramatically for mold growth, wood rot and infestation by insects, reduced efficiency of insulation and corrosion of fasteners. The report attributes the lower moisture content in the wood components to brick’s inherent thermal mass properties, the one-inch air space in the brick veneer wall and the increased thermal absorption of the test brick’s red color.
Moisture performance values were collected at regular intervals from key components within a pair of wall assemblies constructed with eight different cladding types. Each wall assembly consisted of interior gypsum board, wood studs with fiberglass insulation between the studs, sheathed with either OSB or plywood and clad with brick veneer, vinyl siding, fiber cement, manufactured stone or stucco and was then subjected to ambient weather conditions over a one-year period. A portion of water resistant barrier was compromised and the wall assembly behind it subjected to a daily water injection over a five-day period to evaluate its ability to dry after a leak.