- Author
-
Burch, D. M.
|
Thomas, W. C.
|
Mathena, L. R.
|
Licitra, R. A.
|
Ward, D. B.
- Title
- Transient Moisture and Heat Transfer in Multilayer Non-Isothermal Walls: Comparison of Predicted and Measured Results.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
Virginia Polytechnic Institute and State University, Blacksburg
- Book or Conf
- American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Thermal Performance of the Exterior Envelopes of Buildings, 4th Proceedings. ASHRAE/DOE/BTECC/CIBSE Conference. December 4-7, 1990,
Orlando, FL,
513-531 p.,
1990
- Keywords
-
walls
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transient moisture
|
heat transfer
|
mathematical models
|
transient heat
|
moisture transfer rate
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paints
|
insulation
- Abstract
- A distributed-capacity, finite-difference model is presented for predicting the transient heat and moisture diffusion through a multilayer plane wall. The model is one-dimensional and uses a single potential (i.e., water vapor pressure) to predict the moisture transfer rate. This model was used with independently measured moisture properties to predict the results of a simple experiment. Two plane walls, measuring 2 ft by 2 ft by 4.5-in. thick (0.61 by 0.61 by 0.11 m) were exposed to a step decrease in temperature and humidity at their exterior surfaces. The walls were comprised of gypsum board with interior latex paint, cavity insulation, and white pine with exterior oil-base paint. One of the walls was insulated with glass-fiber insulation, the other with cellulose insulation. Moisture was permitted to accumulate within the walls during a 34-day period. The model predicted with good agreement the accumulation of moisture in the wood. Laboratory methods to measure independently the moisture properties of the materials are also described. The effect of moisture accumulation on the overall thermal resistance of the two walls was investigated.