Painted Wood Climate Risk Analysis by the HERIe Model of Building Protection and Conservation Heating Scenarios in Norwegian Medieval Stone Churches

Abstract

HERIe was used to model the effect of changes to indoor climate on the risk of humidity-induced mechanical damage (cracking and plastic deformation) to wooden panels painted with stiff gesso in two Norwegian medieval stone churches: Kinn (mean relative humidity (RH, %) = 79%) on the humid west coast, and Ringsaker (mean RH = 49%) in the drier eastern part of the country. The risk involved in moving cultural heritage objects (paint on wood) between the churches and a conservation studio with more “ideal”, stable conditions was also modeled. A hypothetical reduction in RH to ~65% and, proportionally, of the climate fluctuations in Kinn, and an increase in the RH in Ringsaker to a more stable value of ~63% via conservation heating, were found to improve (Kinn) and uphold (Ringsaker) the conformity to relevant standards and significantly reduce the risk of damage, except in the scenario of moving objects from Ringsaker to a conservation studio, when the risk would increase. The use of conservation heating could save ~50% of the heating cost. The estimated risk reductions may be less relevant for objects kept in situ, where cracks in the original paint and gesso have developed historically. They may be more relevant when moving original objects away from their proofed climate into a conservation studio for treatment.

Tuning and Effectiveness in Heritage Models

“…These have a simple approach to input or graphical user interfaces. This enables researchers and practitioners to engage with a model developed to address a process that impacts heritage materials, such as salt crystallisation and changes in indoor environments [17,18]. It is highly important for experts to produce clear guidance for good practice, as well as avoiding common mistakes for these out-of-the-box models, as users can find the model limitations hard to identify, even though they were obvious to the developer.…”

“…Budgets may be set over three-year timescales, or models might need to be tuned to the lifetime of maintenance and repair [13]. Thus, shorter planning horizons or recommendations for immediately implementable actions [17] will see an increasing need for effective models to consider reduced time periods.…”

“…Time is also important with regard to the resolution of input and output data. Heritage science sometimes uses annual or monthly averages (e.g., [50,51]), but for models to capture processes that drive deterioration, much shorter time scales are often needed, commonly requiring daily [33] or sub-daily data [17,18]. In some cases, it can be possible to extract the higher-resolution data from monthly averages, but this is not always possible [52].…”

“…Heritage models are developed for a wide range of spatial scales from individual materials [28,34], objects and sites [17,29,30], countries and regions [53,54], as well as global-scale analyses [33]. The spatial scale of a heritage model will be determined by the purpose of the model, with strategic models tending to have larger spatial scales, while, for example, chemical changes within heritage materials will require smaller-scale models.…”