Application of Hygrothermal Modeling Tool to Assess Moisture Response of Exterior Walls

Abstract

The moisture design of exterior walls in a building envelope is an important task that needs to be carried out systematically to generate a sustainable and healthy built environment. Many conventional methods or practice guidelines are available for this purpose, based primarily on local traditions and with limited performance assessment records. In recent years, with the rapid development of global free trade and economy, new wall systems and unconventional materials have been introduced in every part of the world for reasons such as aesthetic appeal, cost effectiveness and so on. However, neither the long-term moisture management performance of these new wall systems nor the uses of unconventional materials have been assessed in a systematic way. The primary reason for this lack of assessment is the absence of a design-oriented methodology to perform the task. This paper presents selected results from a recently completed research project that demonstrate that it is indeed possible to assess the moisture management performance of exterior walls in a systematic way, using a hygrothermal modeling tool together with key inputs from a limited number of laboratory and field investigations. In this project the hygrothermal responses of exterior walls and their components were assessed with a novel moisture response indicator, called the RHT index, which is derived from relative humidity and temperature data over a time period. The results and discussion presented in this paper clearly show the need and usefulness of the application of hygrothermal simulation tool for the optimum moisture design of exterior wall systems in various geographic locations, when sufficient information is available from laboratory and field experiments.