The objective of the Hygrothermal Modelling and Analysis Task was to estimate the risk of moisture damage to the structural elements of a mid-rise wood building. Specifically, the objective was to characterize the risk of moisture damage to the load-bearing wall components of two wall constructions specified in “MID-RISE WOOD CONSTRUCTIONS – Specifications of Mid-rise Envelopes for Hygrothermal Assessment” Client Report A1-100035-03.1 [ ] due to trapped construction moisture.
In general for both wall constructions simulation results tended to point to the exterior of the stud in the Lightweight Wood Frame (LWF) and Cross Laminated Timber (CLT) construction cases to be the area most at risk, specifically toward the exterior surface of the stud. Generally the total Moisture Content (MC) of the stud decreased to an acceptable level within the simulation period however the exterior surface appeared to remain at relatively high of moisture content level for significant periods of time. The presence of wood strapping covering the exterior face of the stud seemed to exacerbate the situation. If a support system for the cladding can be designed that does not rely on wood strapping or covers a minimum area of the stud the performance of this critical area could be improved. If the initial moisture content of the wood materials could be reduced before close up the performance would also be improved for all locations that did not show an increase in moisture content and the RHT index in the second year, at least with respect to computer modelling. This work however was not in scope of the work.