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Abstract
Hygrothermal analysis predicts the impact of transient heat and moisture transfer through building envelopes over time. Today, there is specialized software to help the user visualize such factors as surface temperature differences, surface condensation potential, mold growth potential, building material moisture content, and moisture accumulation rates. In addition, the recently published ANSI/ASHARE Standard 160-2009, Criteria for Moisture-Control Design Analysis in Buildings, now provides guidance on how to conduct hygrothermal analysis. The purpose of this paper is to present several illustrations of how to use one-dimensional hygrothermal-modeling techniques provided in ASHRAE Standard 160 to evaluate moisture-related problems in commercial roof and wall systems in various climates. Issues with cool roof surface temperatures, thermal bridging due to fasteners and metal framing, water vapor permeance of vapor retarders and water resistive barriers, as well as the influence of surface temperature on air leakage will be discussed. While the issues described are multidimensional in nature, simplified one-dimensional models can provide valuable information for the performance of the assembly.
Hygrothermal analysis predicts the impact of transient heat and moisture transfer through building envelopes over time. Today, there is specialized software to help the user visualize such factors as surface temperature differences, surface condensation potential, mold growth potential, building material moisture content, and moisture accumulation rates. In addition, the recently published ANSI/ASHARE Standard 160-2009, Criteria for Moisture-Control Design Analysis in Buildings, now provides guidance on how to conduct hygrothermal analysis. The purpose of this paper is to present several illustrations of how to use one-dimensional hygrothermal-modeling techniques provided in ASHRAE Standard 160 to evaluate moisture-related problems in commercial roof and wall systems in various climates. Issues with cool roof surface temperatures, thermal bridging due to fasteners and metal framing, water vapor permeance of vapor retarders and water resistive barriers, as well as the influence of surface temperature on air leakage will be discussed. While the issues described are multidimensional in nature, simplified one-dimensional models can provide valuable information for the performance of the assembly.
Date
3/2010
3/2010
Author(s)
Stanley Gatland II
Stanley Gatland II
Page(s)
91-100
91-100
Source
Roof Consultants Institute
Roof Consultants Institute
Keyword(s)
hygrothermal analysis; heat transfer; moisture transfer; ASHRAE 160-2009
hygrothermal analysis; heat transfer; moisture transfer; ASHRAE 160-2009