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Mathematical Analysis of Moisture and Heat Transfer in the Roof Cavities of Manufactured Housing.


pdf icon Mathematical Analysis of Moisture and Heat Transfer in the Roof Cavities of Manufactured Housing. (1304 K)
Burch, D. M.; Walton, G. N.; Tsongas, G. A.

Challenges of the 21st Century. Roofing Technology, Fourth (4th) International Symposium. Proceedings. First (1st) Edition. U.S. National Institute of Standards and Technology, U.S. National Roofing Contractors Association, Canadian Roofing Contractors Association, National Research Council of Canada, International Waterproofing Association, CIB, RILEM. September 17-19, 1997, Gaithersburg, MD, 390-400 pp, 1997.

Keywords:

roofs; moisture; manufactured housing; air flow; heat transfer; ventilation; standards

Abstract:

A mathematical model is presented that predicts moisture and heat transfer in ventilated cavities such as attics, roof cavities and catherdral ceilings. The model performs a transient moisture and heat balance as a function of time of year and includes the storage of moisture and heat at the construction layers. The model includes both molecular diffusion and capillary transfer within the materials. Radiation exchange among the entilated cavity surfaces is predicted using a mean-radiant-temperature-network model. Airflow from the house into the ventilated cavity is predicted using a stack effect model with aggregated effective leakage areas. Air exchange between the ventilated cavity and outdoor environment is predicted by a semi-empirical model. The relative humidity in the house is permitted to vary during the winter and is calculated from a moisture balance of the whole building.