Abstract
The majority of cultural heritage is stored in archives, libraries and museum storage spaces. To reduce degradation risks, many archives adopt the use of archival boxes, among other means, to provide the necessary climate control and comply with strict legislation requirements regarding temperature and relative air humidity. A strict ambient indoor climate is assumed to provide adequate environmental conditions near objects. Guidelines and legislation provide requirements for ambient indoor climate parameters, but often do not consider other factors that influence the near-object environment, such as the use of archival boxes, airflow distribution and archival rack placement. This study aimed to provide more insight into the relation between the ambient indoor conditions in repositories and the hygrothermal conditions surrounding the collection. Comprehensive measurements were performed in a case study archive to collect ambient, local and near-object conditions. Both measurements and computational fluid dynamics (CFD) modeling were used to research temperature/relative humidity gradients and airflow distribution with a changing rack orientation, climate control strategy and supply as well as exhaust set-up in a repository. The following conclusions are presented: (i) supplying air from one air handling unit to multiple repositories on different floors leads to small temperature differences between them. Differences in ambient and local climates are noticed; (ii) archival boxes mute and delay variations in ambient conditions as expected—however, thermal radiation from the building envelope may have a large influence on the climate conditions in a box; (iii) adopting night reduction for energy conservation results in an increased influence of the external climate, with adequate insulation, this effect should be mitigated; and (iv) the specific locations of the supply air and extraction of air resulted in a vertical gradient of temperature and insufficient mixing of air, and adequate ventilation strategies should enhance sufficient air mixing in combination with the insulation of external walls, and gradient forming should be reduced.
Highlights
Libraries and museum storage preserve the majority of cultural heritage: for a typical museum, around 90% of the collection is placed in storage and 10% is on display
The section starts with results from the ambient indoor climate conditions in the repository tower
While Dutch archival legislation mentions to be careful of placing objects near the floor and ceiling, no mention of adjacent areas with different climate conditions was mentioned [12]
Summary
Libraries and museum storage preserve the majority of cultural heritage: for a typical museum, around 90% of the collection is placed in storage and 10% is on display (https://www.bbc.com/news/uk-england-london-12214145 accessed on 20 February 2021). The indoor climate conditions in these buildings are important to ensure the longevity of objects and reduce degradation risks such as biological, chemical and mechanical degradation. Indoor climates in museum galleries with objects on display are frequently researched. The indoor climate parameters can be disturbed by visitor presence acting as a heat and moisture source [1] and in archives, thermal and hygric inertia of the stored objects could be of influence [2]. A high incorrect T can accelerate the chemical degradation of organic material (e.g., cracking of leather bindings, yellowing of paper). The effect of cleaning procedures in a museum building on the variability of RH was found. The use of water in the cleaning procedure should be minimized to prevent fluctuations [9]
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