Impact of Indoor Air Conditions and Solar Radiation on Moisture Accumulation within Multi-Layer Non-Cavity Walls

Abstract

This paper investigates the impact of indoor temperature, humid ity and solar radiation on moisture accumulation within multi-layer non-cavity walls. A transient model [1] that simultaneously considers both thermal and mois ture transient transfer and their interactions in multi-layer non-cavity wall con structions is utilized. Based on the mathematical formulations and the develop ments of the model, a computer simulation program has been developed in order to investigate the impact of the hygrothermal boundary conditions on wall mois ture behavior. By employing the model, both the moisture transport process and the material moisture content within the different layers of a wall system can be evaluated at all possible material moisture conditions. Evaluation of moisture accu mulation within a typical wall system showed that the impact of boundary condi tions is highly dependent on the thermal and moisture characteristics of the wall components. Indoor temperature has been found to have a relatively considerable influence on moisture accumulation in the insulation layer. The presence of solar radiation can lead to considerable reduction in moisture accumulation.

Keywords

heat moisture solar radiation transient modelling simulation wall systems.

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References

Budaiwi, I. , El-Diasty, R. and Abdou, A. "Modelling of Moisture and Thermal Transient Behavior of Multi-Layer Non-Cavity Wall," J Building and Environment, 34, 1999, 537-551.

Techsel, H.R. , Achenbach, P.R. and Ebbets, J.R. "Effect of Exterior Air-Infiltration Barrier on Moisture Condensation and Accumulation within Insulated Frame Wall Cavities ," ASHRAE Transactions, Vol. 91, part 2,1985, pp. 545-559.

Verschoor,J.D. "Measurement of Water Vapor Migration and Storage in Composite Building Construction," ASHRAE Transactions, Vol. 91, part 2, 1985, pp. 390-403.

TenWolde, A. and Mei, H.T. "Moisture Measurement in Walls in a Warm Humid Climate," Thermal Performance of Exterior Envelopes of Buildings III, Proceedings of the ASHRAE/DOE/BTECC/CIBSE Conference, Orlando, Florida , 1985, pp. 570-585.

Forest, T.W. "Moisture Transfer through Walls," Thermal Performance of Exterior Envelopes of Buildings IV, Proceedings of the ASHRAE/DOE/BTECC/CIBSE Conference, Orlando, Florida, 1989, pp. 532-542.

Spolek, G.A. , Osterhout, G.R. and Apfel, R.I. "Transient Heat and Mass Transfer in Walls," Thermal Performance of the Exterior Envelopes of Buildings, Proceedings of the ASHRAE/DOE/BTECC/CIBSE Conference III, Orlando, Florida , 1985, pp. 634-647.

Burch, D.M. , Thomas, W.C. , Mathene, L.R. , Licitra, B.A. and Ward, D.B. "Transient Moisture and Heat Transfer in Multilayer Non-Isothermal Walls—Comparison of Predicted and Measured Results," Thermal Performance of Exterior Envelopes of Buildings IV, Proceedings of the ASHRAE/DOE/ BTECC/CIBSE Conference, Orlando, Florida , 1989, pp 513-530.

Spolek, G.A. "Computer Simulation of Moisture Transport in Walls of Residences," Proceedings of Building Simulation '91 Conference, Nice, France, 1991, pp. 37-41.

Cunningham, M.J. "The Moisture Performance of Framed Structures—A Mathematical Model," Building and Environment, Vol. 23, No. 2, 1988, pp. 123-135.

10.

Cunningham, M.J. "Modelling of Moisture Transfer in Structures—I. A Description of a Finite-Difference Nodal Model,"J Building and Environment, Vol. 25, No. 1, 1990, pp 55-61.

11.

Cunningham, M.J. "Moisture Diffusion due to Periodic Moisture and Temperature Boundary Conditions—An Approximate Steady Analytical Solution with Non-Constant Diffusion Coefficients,"J. Building and Environment, Vol. 27, No. 3, 1992, pp. 367-377.

12.

TenWolde, A. , Carll, C. and Malinauskas, V. "Airflows and Moisture Conditions in Walls of Manufactured Homes," Proceedings of Airflow Performance of Building Envelopes, Components and Systems ASTM, Technical publication no. 12555, September 1995, pp. 137-155.

13.

De Freitas, V.P. , Brantes, V. and Rausse, P. "Moisture Migration in Buildings Walls—Analysis of the Interface Phenomena," Building and Environment, Vol. 31, No. 2, 1996, pp. 99-108.

14.

Christian, J.E. and Kosny, J. "Thermal Performance and Wall Ratings," ASHRAE Journal, March 1996, pp. 56-65

15.

Burch, D.M. "An Analysis of Moisture Accumulation in Walls Subjected to Hot and Humid Climates," ASHRAE Transactions, Vol. 99,pt.2,1993,pp. 1013-1022

16.

Hagentoft, C-E. and Harderup, E. "Moisture Conditions in a North-Facing Wall with Cellulose Loose-Fill Insulation: Construction with and without a Vapor Retarder and Air Leakage," J Thermal Insulation and Building Envelopes, Vol. 19, January 1996 , pp. 228-243.

17.

TenWolde, A. and Rose, W.B. "Moisture Control Strategies for the Building Envelope," J Thermal Insulation and Building Envelopes, Vol. 19, January 1996, pp. 206-214

18.

Matsumoto, M. , Hokoi, S. and Ka, E. "An Analysis of Coupled Heat and Moisture Transfer in Buildings Considering the Influence of Radiant Heat Transfer," ASHRAE Transaction, Vol. 103, No. 1, 1997, pp 573-583

19.

Jayamaha, S.E.G. "Heat and Moisture Transfer through Building Envelope Components Subjected to Outdoor Weather Conditions Including Rain ," J Drying Technology, Vol. 15, No 5, May 1997, pp. 1653-1656.

20.

Duffie, J.A. and Beckman, W.A. Solar Engineering of Thermal Processes, John Wiley & Sons, New York, 1980.