Extract

A systematic literature review has analysed methods available to assess the risk of condensation from thermal bridges in timber-framed houses. The standard approach comes from Clause E3 in the New Zealand Building Code, which prescribes the minimum overall R-value for timber-framed walls as R-1.5. The standard approach avoids condensation because the amount of timber framing, with an R-value of less than 1.5, makes up a tiny fraction of the overall insulated wall. It does not consider the possibility that sections within the wall may be built up with solid timber creating a much larger thermal bridge than a single timber stud. For example, New Zealand Standard 3604 states trimming studs can be built up to a width of 270mm. EnergyPlus is commonly used to calculate the energy demand. It can calculate surface temperatures and thus the risk of condensation for overall average R-values. Complex moisture programs such as WUFI Plus can be used to estimate condensation potential around local thermal bridges, but this is time-consuming and requires additional expertise. The systematic review identifies the existing state-of-the-art programs like EnergyPlus as potentially less complex tools, that are already in use for energy performance analysis, to predict the risk of local condensation.

Keywords: Thermal bridge; condensation; simulation.

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