Moisture Measurements and Condensation Potential in Wood Frame Walls in a Hot-Humid Climate

Abstract

It has long been noted that interior vapor barriers in wood frame walls in hot-humid climates can lead to interstitial condensation within walls. The bases for this recognition are predictive simulations, anecdotal observations, and a limited number of experimental studies. This paper describes an experimental study conducted in a hot-humid climate that investigated the influence of an interior vapor retarder and compares observed performance with simulation predictions. The wall performance data reviewed here was gathered as part of a larger test program evaluating the performance of a range of typical wood frame, residential wall constructions in a hot-humid climate. The approach chosen was to use real-time field exposure using a “test hut” located in Tampa, Florida. The test hut had two long sides, which provided the ability to test 16 wall specimens each. Wall specimens were instrumented with a variety of temperature, humidity, and moisture sensors. In addition to natural weather exposure, the wall specimens could be manually wetted by a water injection system to simulate rain leakage. More specifically, this paper focuses on using the data collected before and after the installation of an interior vapor barrier (vinyl wallpaper) to show the change in moisture loading and the potential condensation within the walls resulting from the installation. The field data is compared with predictions of the wall behavior using a commonly available hygrothermal model. There is increasing reliance on the use of predictive models to assess the moisture performance of building assembly designs. These predictive models need to be validated against real data to test their variance from real systems.

Design hygrothermally functional wooden insulation systems: A parametric study for mixed climate

“…This calculation method complies with EN 15026 (EN 15026: 2007, 2007), and its validation has been conducted, for example, by (Coelho et al, 2018; Künzel et al, 2005). In addition, this software is extensively applied for hygrothemal simulation, such as in North America for simulation of wood-frame wall assemblies (Glass et al, 2015; Pazera et al, 2011; Trechsel, 2001; Weston et al, 2011) and for historic buildings in Germany (Kilian, 2013).…”

Moisture Performance of Energy-Efficient and Conventional Wood-Frame Wall Assemblies in a Mixed-Humid Climate

“…The test wall assemblies described above were simulated using WUFI ® Pro 5.2 Software (Fraunhofer Insitute for Building Physics, Holzkirchen, Germany) for one-dimensional transient heat and moisture transfer [38,39] ("WUFI" stands for wärme und feuchtetransport instationär, German for "transient heat and moisture transport"). This software has been used extensively in North America for simulation of wood-frame wall assemblies [18,36,[40][41][42][43][44][45][46][47]. One-dimensional hygrothermal simulations are often used by practitioners in North America for building envelope design analysis.…”