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

Abstract

Long-term moisture performance is a critical consideration for design and construction of building envelopes in energy-efficient buildings, yet field measurements of moisture characteristics for highly insulated wood-frame walls in mixed-humid climates are lacking. Temperature, relative humidity, and moisture content of wood framing and oriented strand board (OSB) structural panel sheathing were measured over a period from mid-November 2011 through March 2013 in both north-and south-facing orientations in test structures near Washington, DC, USA. Wall configurations varied in exterior cladding, water-resistive barrier, level of cavity insulation, presence of exterior continuous insulation, and interior vapor retarder. The combination of high interior humidity and high vapor permeance of painted gypsum board led to significant moisture accumulation in OSB sheathing during winter in walls without a vapor retarder. In contrast, wintertime moisture accumulation was not significant with an interior kraft vapor retarder. Extruded polystyrene exterior insulation had a predictable effect on wall cavity temperature but a marginal impact on OSB moisture content in walls with vinyl siding and interior kraft vapor retarder. Hygrothermal simulations approximately captured the timing of seasonal

In-plane shear modulus of extruded polystyrene foam measured by the torsional vibration, square-plate twist and simple shear methods

“…Additionally, XPS is widely used in construction such as core materials of sandwich wall panels [17][18][19][20][21][22][23][24] and geofoams [25][26][27] because the lightweight nature of XPS is effective for the attenuation of seismic forces. Nevertheless, there is a concern that large deformation and failure are often induced in XPS under static or dynamic forces because of the low mechanical properties of XPS.…”

Stochastic modelling of hygrothermal performance of highly insulated wood framed walls

“…However, the highly insulated walls may lead to a higher risk of moisture problems. Hygrothermal simulations have been widely used to investigate the hygrothermal performance of highly insulated walls (Maref et al, 2010;Arena et al, 2013;Parsons and Lieburn, 2013;Smegal et al, 2013;Craven and Garber-Slaght, 2014;Glass et al, 2015). However, the uncertainties of the input parameters may lead to discrepancies between simulation results and real performance of the walls.…”

A rule-based expert system applied to moisture durability of building envelopes

“…risk due to the lack of a ventilated cavity behind the cladding; however, the experimental results from the paper showed that the MC of the OSB sheathing stayed below 16% for this wall. Glass et al (2015) tested 15 different walls with north and south orientations with various claddings, continuous insulation, WRBs, cavity depth, and interior VRs. Field tests for over 1 year showed that all north-facing walls without an interior VR of at least class II showed OSB sheathing MC over 20% for much of the year.…”