Our Lord in the Attic: A Case Study

Current indoor climate (1990 - present)

Central heating on the first gallery of the church (photo: TU/e)The museum is nowadays heated by means of 2 gas stoves and a central heating system, of which there are no installation drawings. The gas stoves are located on the ground floor in the antechamber and one in the canal room. Fumes/smoke are extracted by chimneys. Technical University Eindhoven (TU/e) investigated the present installation in the building and compiled their findings in a report.

Data logger in church (photo: TU/e)enlarge

Data logger in the church (under Lamp of God - low)

donwload Climate data in church (XLS, 3.0MB)

donwload Climate data sael (XLS, 1.2MB)

Climate data canal room (XLS, 1.2 MB)

c Outdoor climate data (XLS, 1.1 MB)


Current indoor climate

Data logger ('under godlamp high') in the church (photo: TU/e)From January 1st 2005 up to January 2006, climate data have been collected by the ICN with collaboration of the Technical University Eindhoven (TU/e). Relative humidity (RH) and temperature (T) data have been collected using Hanwell sensors placed at different locations throughout the building:

In addition air exchange rate measurements were taken by the TU/e.

Water added by visitors and (de)humidifiersenlarge

Graph depicting the amount of added water to the indoor air by the humidifiers (black) and the visitors (red)


donwload Water added and extracted from building (XLS, 63KB)

Localized humidity control

Humidifier (photo: TU/e)In the early 1990's, the museum acquired localized humidity control equipment (humidifiers and dehumidifiers). Several humidifiers and dehumidifiers were placed throughout the building. These are still present and in function today.  Their location is more or less permanent. Only in special instances, such as an exhibition, are they moved. During the period in which the indoor climate was monitored (January 1st 2005 until January 2006), the humidifiers and dehumidifiers were set to maintain a 50% RH environment by respectively adding or removing moisture from the air.

A data set (April 12, 2005 – June 29, 2006) of the recorded amounts of water supplied to the humidifiers and removed from the dehumidifiers was analyzed. During this time, the relative humidity in the building was kept between 40 and 55% (and the majority of the time between 45 and 50%) at a stable temperature of approximately 20°C. The total amount of water added for the entire period is 14,846 liters.

The relative humidity often exceeded 60% in the building during summer months, although daily average values remained less than 60%. Therefore, it was determined that instances when the relative humidity exceeded 60% were caused by a combination of peaks in the visitation and humid outdoor conditions. Large amounts of humid air infiltrated the building during hot and rainy days as a result of large numbers of visitors entering and exiting from the building. The available dehumidification capacity was not adequate to control the environment under these circumstances.

© J. Paul Getty Trust / Netherlands Institute for Cultural Heritage / Museum Ons' Lieve Heer op Solder