A new research project to offer builders guidance for constructing more durable, moisture-tolerant exterior wall assemblies sheathed with wood-based material and clad with absorptive siding has been launched by the NAHB Research Center. The center is working with the Forest Products Laboratory, U.S. Department of Agriculture and the U.S. Department of Housing and Urban Development in the study.
Currently, moisture effects in modern residential exterior wall assemblies with absorptive cladding materials are not well understood within the industry, according to the NAHB. Residential builders are often encouraged by home buyers and designers to apply exterior claddings that look good-without knowing how the assembly will perform over time when exposed to local climatic conditions. This partially explains why moisture problems in many types of exterior walls have increased in recent years.
While the number of wall construction techniques and materials continues to grow, direction on proper applications for moisture protection in each climate remains hard to find, according to the Research Center.
The center’s new research effort aims at identifying robust design rules and best construction practices for moisture-tolerant exterior walls in a mixed humid climate. Some recently developed assembly types–such as synthetic stone–and various stucco assemblies will be compared to a vinyl siding baseline to determine which are more moisture-resistant.
Wall panels will then be installed in a climate-controlled test structure at the NAHB Research Center’s facility, which will simulate occupied indoor conditions on the interior, with the exterior cladding exposed to the environment for one year. Detailed monitoring will measure wood moisture, humidity, temperature, precipitation, wind and solar intensity.
NAHB TESTING MOISTURE RESISTANCE OF CLADDING
December 5, 2007