Condensation and mould growth is reported as being a problem in an estimated 4.2 million dwellings in England resulting in poor occupant health and substantial damage to the building fabric. This paper examines the development of an algorithm, Condensation Targeter, to predict the internal surface relative humidity and risk of mould growth in dwellings. The impact of cold bridging, seasonal variations, variable moisture production and hygroscopic materials are reviewed (but not interstitial condensation) and a comparison between modelled and measured data for 36 dwellings carried out. Results indicate that a steady-state model utilising Bredem-8 to predict internal temperatures and Loudon's condensation model to predict moisture shows good (± 10%) agreement with monitored data. A model sensitivity study shows that variations in occupant heating and density can be as, or even more, important in determining mould growth than ventilation.
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