Sensitivity and Uncertainty analyses on a DELPHIN model: the impact of material properties on moisture in a solid brick wall

¹ UCL Energy Institute, Central House, 14 Upper Woburn Place, London, United Kingdom
² UCL Institute for Environmental Design and Engineering, 14 Upper Woburn Place, London, United Kingdom

^* Corresponding author: n.grint@ucl.ac.uk

Abstract

This paper presents sensitivity and uncertainty analyses on a DELPHIN model, which is representative of a case study wall in real climatic conditions. Results of the Differential Sensitivity Analysis (DSA) show properties governing liquid water transported into, through and stored in the wall impact most on moisture accumulation, affecting relative humidity (RH) outputs by 10 – 35% at three different locations in the wall. Parameters affecting vapour transport into the room also influence RH outputs at the inner location, but less than rain amount and rain exchange coefficient. A probabilistic uncertainty study is then used to explore key material functions, parameterised as four sets of co-ordinates and varied randomly. The correlation between the parameter inputs and the resulting change in RH is assessed. There are some surprising divergences from the DSA, including the significance of moisture storage in the plaster layer in the presence of liquid. Low correlation coefficients suggest numbers of variables could be reduced to further clarify the effects of these parameters, and interesting questions are raised on the parameterisation of material functions to represent the uncertainty in the characterisation of real walls.