Modelling of the deterioration and conservation costs of polychrome painted wood in two Norwegian medieval stone churches.

• Modelled damage rates of painted wood in Norwegian churches compared to observed cost. • Painted wood damage in church climate mitigation and deterioration rate scenarios. • EnvCul (https://envcul.nilu.no/) modelling of painted wood heritage damage rates. • Relevance of HERIe (https://herie.pl/) modelling to observed painted wood damage. • Conservation costs explained by gradual or late rather than early critical damage. EnvCul (https://envcul.nilu.no/) modelling was performed of condition changes of painted wooden panels and related conservation cost in indoor climate and object response scenarios in two Norwegian Medieval stone churches: Kinn (mean relative humidity = 79%) on the humid west coast, and Ringsaker (mean RH = 49%) in the drier eastern part of the country. It was found that, hypothetical, building measures in Kinn, and conservation heating measures in Ringsaker, to approach an indoor RH of about 65% in the two churches, could probably increase conservation intervals with 20–100%, and correspondingly reduce conservation costs between 10% and 50%. This is in reasonable agreement with an available report of observed conservation requirements in differently heated Norwegian churches. A situation between a linear and accelerating development of the deterioration of the painted wood on approaching a new conservation intervention gave the best correspondence to the observed values. The large modelling uncertainty was mainly due to lacking observations of the deterioration development, but also lacking understanding of the complex mechanisms and phases of the environmental dose-deterioration response of painting conservation treatments. [ABSTRACT FROM AUTHOR]