Contamination of a church ceiling due to the burning of candles in combination with floor heating

An air heating system originally heated St. Martinus’ church in Weert. Together with a large restoration in 1984 a floor heating system replaced this heating system. After this major renovation a number of problems arose: due to the floor heating system and massive granite floor the church could only be heated stationary. A relatively large thermally driven vertical airflow was the result of it, which lead to thermal discomfort. The air temperature therefore was set rather high. The combination of a large soot production, due to the burning of ten thousands of candles, and the thermally driven vertical air flows lead to a most serious contamination of the 16th century painted ceiling. Furthermore due to the high floor and air temperatures the energy costs were massive. For many years this church has been monitored. The ceiling paintings are restored at this moment and a number of measures has been taken to prevent the contamination in future. To predict this future contamination an experimental setup has been developed more than two years before the start of the restoration. This setup consists of two round disks with contamination samples which have been placed in two large openings in the church ceiling, now for more than two years ago. The disks have been prepared for a number of physical measurements of air and surface temperatures, heat fluxes, relative humidities and air velocities. These measurements were monitored nearly continuously since then. The ongoing contamination of the samples has been measured optically with intervals of about three months. A lot of effort has been invested in the design of the measurement setup. The contamination of the samples e.g. should give a good representation of the contamination of the ceiling. Furthermore the existing geometry and airflow boundary conditions should not be disturbed by the measurement setup. The design and results of this measurement setup will be presented in the paper.