Paper Conference

Proceedings of eSim 2002: 2nd Conference of IBPSA-Canada


Importance of Moisture Control in Building Performance

Achilles Karagiozis

Abstract: The number and frequency of moisture-related premature failures in exterior wall systems has called into question current design and construction practice, materials use, and building code requirements. Many questions have been raised as to whether more rugged materials, more robust assemblies, and revised building codes are needed for climate regions subject to higher moisture loads. A Seattle research project titled, “Building Enclosure Hygrothermal Performance Study” has been initiated by the moisture-damage committee formed by the Department of Design, Construction and Land Use (DCLU) for the city of Seattle. This committee will assess the performance of current and past typical wall constructions. In the first phase of this project, we analyzed heat, air, and moisture performance of a set of (primarily stucco-clad) wall systems. A new “moisture engineering approach” was adopted in the project. Moisture engineering analyzes hygrothermal loads from vapor, water, heat, and pressure. In addition to these loads, water penetration data are also included to provide realistic assessments of the performance of building envelope systems. This paper reports on moisture engineering as performed using Oak Ridge National Laboratory’s (ORNL’s) state-of-the-art hygrothermal model, MOISTUTE-EXPERT. Transient two-dimensional analysis was performed using hourly weather and interior environment data. Data on the sensitivity of water penetration are also shown for a few selected walls in the Seattle research project. This paper describes only part of the overall project that investigated the response of the walls as a function of weather-resistive barriers, wall venting or ventilation, and the influence of interior moisture generated by the building’s inhabitants. The research results also have implications for the need to re-evaluate building codes and their influence on building material durability.