Abstract
Timber buildings, including cross laminated timber (CLT), are gaining market shares globally, mainly due to anticipated environmental benefits, but a new technical solution also raises new questions. Durability is critical to obtain real sustainable constructions built for the future. There are field studies concerning hygrothermal conditions of timber structures, however, there is a lack of documented experiences combining hygrothermal conditions, mould growth potential and weather protection during construction using CLT. The use of full weather protection is being debated in the building industry as well as in the research community, due to lack of knowledge of the combined effects. How does weather protection during the construction affect hygrothermal conditions and risk of mould growth in a CLT structure? A case study using a weather protected six-storey CLT building was performed. The hygrothermal conditions – indoors and outdoors – were monitored during construction and samples from CLT were analysed with respect to mould. The results were analysed together with simulations of mould growth using actual hygrothermal conditions. Theoretical conclusions show the weather protection gives significantly improved conditions resulting in lower potential of mould growth compared to outdoor conditions. The results also show lessons to be learned concerning planning of the construction site.
Highlights
Issues of moisture conditions during construction of cross laminated timber buildings are being debated in the building industry and research community, e.g., [1]
The results indicate a moderate risk for mould growth at the end of the studied period for the cross laminated timber (CLT) components within the weather protection
The CLT construction in the studied case was not exposed to critical moisture levels during the construction phase which was confirmed by the mould growth sampling
Summary
Issues of moisture conditions during construction of cross laminated timber buildings are being debated in the building industry and research community, e.g., [1]. The instructions for handling of the products with respect to moisture given by the suppliers of CLT are not specific in this question as shown in [2] Instead, they are typically qualitatively expressed as variants of: ”protect from weather conditions” and: “take note of weather conditions while unloading”. The CLT-handbook, US-edition [3] states “CLT panels, similar to other wood products, should always be protected from exposure to rain, snow, and wet ground during transport, jobsite storage, and construction process ...”. This is suggested to be achieved with e.g., minimizing exposure time, temporary protection of panels and swift installing of exterior protection (i.e., WRB).
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