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A prarmeteric study of wall moisture contents using a revised variable indoor relative humidity version of the "MOIST" transient heat and moisture transfer model

Tsongas, G., Burch, D., Roos, C., and Cunningham, M. J.
1995
Thermal Performance of the Exterior Envelpes of Building VI, Dec. 4-8, Clearwater Beach, FL
heat transfer; moisture; humidity; walls; computer models; MOIST

Tsongas, G., Burch, D., Roos, C., and Cunningham, M. J., (1995), "A prarmeteric study of wall moisture contents using a revised variable indoor relative humidity version of the "MOIST" transient heat and moisture transfer model", Thermal Performance of the Exterior Envelpes of Building VI, Dec. 4-8, Clearwater Beach, FL.
Abstract:
http://fire.nist.gov/bfrlpubs/build95/art074.html

Abstract:

The present 2.1 version of the "MOIST" software predicts wall moisture contents and associated parameters using an assumed indoor relative humidity input that is constant for the duration of the simulation period. The authors modified the model to calculate the hourly indoor relative humidity during the heating season as a function of outdoor weather conditions, indoor air temperature, building size and airtightness, and indoor moisture generation rate. These changes were accomplished by incorporating within MOIST an indoor moisture balance and a single-zone infiltration model. The modified version of MOIST allows the summer indoor relative humidity to either float to simulate open windows/doors or to be fixed to simulate air conditioning. The new version has the advantage of incorporating many more inputs that influence the indoor relative humidity and construction-layer moisture content results. The development and details of the revisions are described. This enhanced version of MOIST was subsequently used to investigate moisture accumulation in a 5-cm by 15-cm (2-in. by 6-in.) wood-framed wall exposed to a number of different winter climates. Predictions with a constant indoor relative humidity were compared to those with a "floating" or variable indoor relative humidity. The results generally are different, with the results of the revised version agreeing closely with field measurements. In addition, the variable indoor relative humidity program was used to analyze the effect of building airtightness, the indoor moisture generation rate, and the existence of exfiltration. The need for an interior vapor retarder in walls exposed to cold climates also was examined. Moreover, the effects of exterior insulating sheathing and an exterior vapor retarder were modeled. Results and findings are presented along with pertinent conclusions regarding appropriate building construction techniques in winter heating climates.
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Author Information and Other Publications Notes
Tsongas, G.
  1. A computer analysis of the moisture performance of roof constructins in the U.S. DOE Moisture Control Handbook
  2. A field study of indoor moisture problems and damage in new northwest homes
  3. Case Studies of Moisture Problems in Residences
  4. Field observations and laboratory tests of water migration in walls with shiplap hardboard siding
  5. Tri State homes: a case study of extensive decay in the walls of older manufactured homes with exterior vapor retarder  
Burch, D.
  1. A computer analysis of the moisture performance of roof constructins in the U.S. DOE Moisture Control Handbook
  2. A mathematical analysis of moisture and heat transfer in the roof cavities of manufactured housing
  3. An analysis of moisture accumulation in the roof cavities of manufactured housing
  4. Computer analysis of wall constructions in the moisture control handbook
  5. Empirical validation of a transient computer model for combined heat and moisture transfer
  6. Experimental verification of a moisture and heat transfer model in the hygroscopic regime
  7. Heat and moisture transfer in wood-based wall construction: measured versus predicted
  8. Indoor ventilation requirements for manufactured housing
  9. Manufactured housing walls that provide satisfactory moisture performance in all climates
  10. MOIST: A PC program for predicting heat and moisture transfer in building envelopes, Release 3.0
  11. Water vapor permeability measurements of common building materials
  12. Water vapor sorption measurements of common building materials
  13. Water-vapor measurements of low-slope roofing materials  
Roos, C.
  1. Predicting psychrometric conditions in biocontaminant microenvironments with a microclimate heat and moisture transfer model - description and field comparison  
Cunningham, M. J.
BPANZ, Moonshine Road, Judgeford, Private Rag 50908, Porirua, New Zealand. Department of Building Physics at Chalmers University of Technology, G6teborg, Sweden
  1. A field study of the moisture performance of roofs of occupied newly constructed timber framed houses
  2. Effective penetration depth and effective resistance in moisture transfer
  3. Inferring ventilation and moisture release rates from field psychrometric data only using system identification techniques
  4. Modelling of Moisture Transfer in Structures-III. A Comparison between the Numerical Model SMAHT and Field Data
  5. Predicting psychrometric conditions in biocontaminant microenvironments with a microclimate heat and moisture transfer model - description and field comparison
  6. The building volume with hygroscopic materials--an analytical study of a classical building physics problem
  7. Using hygroscopic damping of relative humidity and vapour pressure fluctuations to measure room ventilation rates  


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