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WUFI Moisture Modelling for British Gypsum

British Gypsum appointed us to conduct a heat and moisture transfer analysis using WUFI relative to a product specification. The requirement for this analysis was to assess the hygrothermal performance of an internal insulation system in the context of all the wind-driven rain exposure zones in the UK and examine methods in order to ensure that the system will not involve any moisture-related risk.

The examined internal wall insulation (IWI) system was assessed by creating baseline modelling cases which included installation on solid brick walls with lower absorption bricks and higher absorption bricks and installation on stone walls, in the 4 different wind-driven rain exposure zones.

These baseline cases were analysed and assessed against:

  • Summer condensation (reverse diffusion)

In order to assess the difference in the performance of the build-up with less severe conditions (reduction in wind-driven rain in winter but lack of solar radiation, which decreases the opportunity for the build-up to dry out).

  • Effect of brick cream

In order to assess the impact of brick cream on the IWI system and check if the limits of applicability of this system can be extended.

  • Effect of high internal moisture load

In order to assess the impact of inadequate ventilation on the hygrothermal performance of the IWI system.

  • Effect of imperfect external finish

Each case was run with the following rain penetration factor, to assess the effects of moisture ingress from outside on the performance of the IWI.

– Scenario with a 0.5% rain penetration factor

– Scenario with a 1% rain penetration factor

– Scenario with a 1.5% rain penetration factor

WUFI Moisture Modelling for British Gypsum
WUFI Moisture Modelling for British Gypsum

The conclusions of this hygrothermal performance assessment were summarised and recommendations made regarding the specification of the product, in order to achieve its applicability without any moisture-related risk in the climate context of the whole UK.


“It’s a pleasure to work with Enhabit, very approachable and knowledgeable”

John Humphreys, British Gypsum


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