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A note about passive museum storage

Updated: Feb 28, 2018


Author: Estelle De Bruyn

When we talk about “passive” storage, we often think of heavy buildings with thick walls – providing high thermic and hygroscopic inertia. This idea emerged form the first tests of "passive" climate storage, carried out in historic buildings, which were already used for storing archives or manuscripts. This is the case of the St. Catherine’s Monastery in Sinai, which houses for over 1500 years a library of precious manuscripts. The "natural" climate is warm (20 to 30° C) and dry (15 to 30% RH), however less than the desert climate. Another example is the Alcazar of Segovia, Spain. The cellar is used as a storage for military archives: the average annual temperature is around 10 to 15° C, and the RH is regulated by the massive presence of hygroscopic materials: the archives themselves. Compared with the outside temperature, which has quite extreme values ​​(from 0 to 30° C), the indoor climate is surprisingly stable (Larsen, s.d.).


If the storage climate of these two buildings is considered as stable, it should be noted that it is not suitable for all objects. Some artworks require very strict climatic conditions, with stable relative humidity and temperature values. This is not impossible, and it has already been done: recently, studies have been carried out on passive operating storage (1). Taken the example of a passive storage built in Denmark in 2003, which was studied three years later to check the stability of the prevailing environmental climate. Standard dehumidification and heating systems have been installed so that they can be switched on if the relative humidity and / or temperature values ​​are too extreme (2). The study demonstrated that after a period of stabilization and the use of dehumidifiers and heating during periods of extreme outside temperatures, it is possible to achieve a climate corresponding to an "A" level on the ASHRAE scale (Rasmussen, 2007) (3).


The degree of control "A" is the recommended level when preserving collections. It should be noted that, for museums built on traditional standards, maintaining these conditions of relative humidity and temperature can be extremely difficult since it requires constant monitoring of environmental conditions if the room is poorly insulated. a very expensive and energy-consuming air conditioning system (THE GETTY CONSERVATION INSTITUTE, 2007).


By valuing the thermal inertia and hygrometric stability of the building and using dehumidifiers and heating for periods of critical relative humidity values, it is possible to achieve stable climatic conditions at reduced costs (in comparison with standard climate control), and with a neutral ecological footprint (Baker, 1999). These points address some of the main problems faced by museums, namely the lack of autonomy vis-à-vis financial, energy and technological resources, without however abandoning the quality of the conditions of conservation of their collections. The museum would free itself from this financial chasm that was the operation and maintenance of its climate apparatus and, if necessary, could reinvest the money released in other missions, this time directly related to its mandate (Brophy, 2008).





Figure 1: Sint Catherine’s Monastery in Sinaï, s.d., on the Wikimedia website (online) (available on: https://commons.wikimedia.org/wiki/File:Saint_Catherine_Sinai.jpg, consulted on Oct. 22, 2017). © Joonas Plaan.




Figure 2: Alcazar of Segovia, Spain, s.d., on the Alcazar of Segovia website (online) (available on: http://www.alcazardesegovia.com/en/, consulted on Oct. 22, 2017).




Figure 3: Thermohygrometrical measures of HR and temperature of one of the storage rooms of the Center for Preservation of Cultural Heritage in Vejle, recorded during one year. The light grey and medium grey shows the exterior climate variation. RASMUSSEN, 2007.




Figure 4: The degree of control “A” on the ASHRAE scale: “The relative humidity is ramped down during the fall period from a summer level of 60% to a winter level of 40%, and then ramped up again in the spring. These changes are gradual over a period of a couple of months, rather than abrupt. The temperature is ramped down during the summer and fall period from a summer level of 25°C to a winter level of 10°C, and then ramped up again in the spring. These changes are gradual over a period of 3 months, rather than abrupt.” CANADIAN CONSERVATION INSTITUTE, s.d.



Notes :

(1) Thermal and hygroscopic inertia allowed by the insulation of the building. The type of energy supplying the dehumidifiers and the heating is not specified. These control systems have been installed as safety, in case the internal climate could not be stabilized, but still need to be used regularly to mitigate the very low outdoor temperatures in winter. LARSEN (Poul Klenz), e. a., “Ten years experience of energy efficient climate control in archives and museum stores”, s.d., s.p., on the Conservation Physics website (online) (available on: http://www.conservationphysics.org/musdes/tenyearexp.php, consulted on Oct. 22, 2017).


(2) In another article, the authors pointed out that, for our European climates and considering a building hosting human activities – even reduced to their minimum – it is a necessity. Without this, it is estimated that the relative humidity will reach 75% because of the summer climate. CHRISTENSEN (Jørgen Eric), JANSSEN (Hans), “Passive hygrothermal control of a museum storage building in Vejle”, in Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November, International Building Performance Simulation Association, Sydney, 14-16 November 2011, 7 p. (available on: http://orbit.dtu.dk/en/publications/passive-hygrothermal-control-of-a-museum-storage-building-in-vejle(1f014358-53e5-4697-8109-2550844623a6).html, consulted on Oct. 17, 2017).


(3) The Canadian Conservation Institute (CCI), describes the level A as followed: “The letter "A" was assigned to this specification because it was felt to be the most cost-effective degree of control for most collections, given the ability and mandate to provide a climate-controlled building. Such systems will probably operate within AA levels most of the time. To stay reliably within A conditions year-round is a resource-intensive task in most climates. The larger seasonal adjustments in set points are a recognition that even major museums must face energy and sustainability constraints, and that these suggested temperature changes are not a significant risk.” CANADIAN CONSERVATION INSTITUTE, “Classes of control”, in Museology and conservation, Preservation et conservation, Preventive conservation and risks, Preventive conservation, Environmental guidelines for museums, on the Canadian Conservation Institute (CCI) website (online), available on: http://canada.pch.gc.ca/fra/1444920475504/1444920475506 (consulted on Oct. 17, 2017).


References :

BAKER (Jennifer), LUGANO (Fred), A Passive Approach to Practical Climate Control, in 1999 WAG Postprints, The American Institute for Conservation of Historic & Artistic Works (AIC), Missouri, 1999, 12 p. (available on: www.wag-aic.org/1999/WAG_99_baker.pdf, consulted on Oct. 10, 2017).

BROPHY (Sarah), WYLIE (Elizabeth), The Green museum, a primer on environmental practice, Altamire Press, Danvers, 2008, 225 p.

CANADIAN CONSERVATION INSTITUTE, “Classes of control”, in Museology and conservation, Preservation et conservation, Preventive conservation and risks, Preventive conservation, Environmental guidelines for museums, on the Canadian Conservation Institute (CCI) website (online), available on: http://canada.pch.gc.ca/fra/1444920475504/1444920475506 (consulted on Oct. 17, 2017).

CHRISTENSEN (Jørgen Eric), JANSSEN (Hans), “Passive hygrothermal control of a museum storage building in Vejle”, in Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November, International Building Performance Simulation Association, Sydney, 14-16 November 2011, 7 p. (available on: http://orbit.dtu.dk/en/publications/passive-hygrothermal-control-of-a-museum-storage-building-in-vejle(1f014358-53e5-4697-8109-2550844623a6).html, consulted on Oct. 17, 2017).

THE GETTY CONSERVATION INSTITUTE, “Experts’ Roundtable on Sustainable Climate Management Strategies”, The Getty Conservation Institute, Los Angeles, 2007, 99 p. (available on: http://www.getty.edu/conservation/our_projects/science/climate/roundtable_transcript.pdf, consulted on Oct. 22, 2017).

LARSEN (Poul Klenz), e. a., « Ten years experience of energy efficient climate control in archives and museum stores », s.d., s.p., on the Conservation Physics website (online) (available on: http://www.conservationphysics.org/musdes/tenyearexp.php, consulted on Oct. 22, 2017).

PADFIELD (Tim), Conservation Physics website, An online textbook in serial form (online) (available on: http://www.conservationphysics.org/standards/standardtemperature.php, consulted on Oct. 17, 2017).

RASMUSSEN (Machael Højlund), “Evaluation of the climate in a new shared storage facility using passive climate control”, in Museum Microvclimates, T. Padfield & K. Borchersen, Denmark, 2007, pp. 207 à 212 (available on: conservationphysics.org/mm/rasmussen/rasmussen.pdf, consulted on Oct. 17, 2017).

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Sustainability in Conservation is an online network providing resources and information about environmentally responsible practices  in art conservation and related fields. Within a practice that produces so much waste, we hope to inspire collaboration and awareness to make cultural heritage a more sustainable profession. 

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