This white paper outlines a study, using WUFI hygrothermal modelling, into the likelihood of mould growth in conventionally insulated timber wall constructions and those insulated with Kooltherm rigid insulation. In New Zealand, there is a perception that if constructions do not have low vapour resistance, then moisture will become trapped within a building and its walls leading to mould growth problems.
WUFI hygrothermal modelling of wall constructions, with Kooltherm rigid insulation sheathing or internally lining a 90mm deep timber frame, resulted in a mould growth index lower than the conventional wall constructions with just bulk insulation between studs. Kooltherm K12 Framing Board, sheathing a timber frame helps keep the whole timber frame warm and can thus reduces the relative humidity within the timber frame and the risk of mould growth. Kooltherm K17 Insulated Plasterboard internally lining a timber frame can reduce the amount of water vapour diffusing into the timber frame and thus the relative humidity within it, and, as a consequence, the risk of mould growth, even though the timber frame as a whole is relatively cold.
This defies the common perception that rigid insulation will magnify or cause mould growth issues in buildings. Kingspan Insulation believes that overgeneralising mould growth risks can be misleading.
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