Conservation Climate Analysis of a Church Containing Valuable Artworks

Abstract

The OLV Hemelvaart church in Watervliet dates back from the 16th century and contains valuable panel paintings and wooden artefacts. They need to be preserved in a stable conservation climate. However, due to the old air heating system, the indoor climate is not stable at all. The air heating system creates sudden strong rises in temperature and due to the position of the supply and extraction grilles, the warm air is not evenly distributed throughout the church. Furthermore, the church suffers from moisture problems such as rain penetration and rising damp. In view of improvement measures to the heating system, from March 2012 to March 2014, the temperature and relative humidity was measured on different locations in the church. The ASHRAE conservation classes were used to analyze the data. Both a frequency analysis and an analysis of the short term and seasonal fluctuations of temperature and relative humidity were performed.It was found that the relative humidity of the indoor air was far too high for conservation purposes: during more than 50% of the time a value above 75% was registered in the middle of the church. During a period of two months, the church was permanently heated in order to improve the conservation climate. Compared to the intermittent heating regime, permanent heating caused a more stable climate: the relative humidity level exceeded 75% during 20% of the time, but it remained almost constantly between 60% and 75%. This was attributed to the church walls that acted as a constant moisture source during heating.