NIST Computer Program Helps Predict, Solve Moisture Problems in Walls, Ceilings

Researchers at the National Institute of Standards and Technology, along with colleagues at the Virginia Polytechnic Institute and State University, have developed a user-friendly computer program called MOIST that predicts moisture accumulation in walls and ceilings.

"Controlling moisture in walls and ceilings is vital to designing energy-efficient, healthy buildings," says Hunter Fanney, a mechanical engineer in NIST's Building and Fire Research Laboratory. Too much moisture can cause nails to pop; paint to blister; wood beams to bow, shift or decay; insulation to thermally degrade; and indoor air quality problems, says Fanney.

For example, in 1992, a courthouse in Polk County, Fla., was closed for renovations costing $16 million--almost half of the original cost of the building. The problem: moisture trapped in the walls and ceilings allowed mold and mildew to grow causing a serious indoor air quality problem. Three hundred of the 600 courthouse employees filed workman compensation claims; 11 were diagnosed with a chronic respiratory ailment similar to asthma.

While the Polk County courthouse is an extreme case, a study by the Building Research Council at the University of Illinois found that one out of 18 houses experiences major moisture- related damage. And, the American Hotel and Motel Association estimates that mold and mildew problems cost $68 million each year in lost revenues and damage repair.

With MOIST, users can define a wall, cathedral ceiling or low-slope roof construction, and then vary the type and placement of building materials. MOIST can determine whether a vapor retarder is needed and, if so, where it should be placed. It also can be used to evaluate the effect various paints and wall coverings have on moisture accumulation.

In addition, MOIST allows users to electronically "move" a wall or ceiling to different U.S. and Canadian cities to investigate the effect of climate on moisture accumulation. Hourly weather data for six U.S. cities are provided with MOIST. Weather data for 40 other U.S. and five Canadian cities are available from the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

"This flexibility will allow builders and designers to simulate wall and ceiling systems in any climate and decide whether or not they will have moisture problems," says Fanney.

Fanney and his colleagues believe MOIST also will be a good tool for developing construction guidelines and practices for controlling moisture in buildings.

Free copies of the MOIST software package are available by writing to Doug Burch, B320 Building Research Building, NIST, Gaithersburg, Md. 20899-0001.

A non-regulatory agency of the Commerce Department's Technology Administration, NIST promotes U.S. economic growth by working with industry to develop and apply technology, measurements and standards.