Energy Savings and the Preservation Environment

PEM2 Monitoring during IMLS experimentThe current economic downturn in the US and Europe along with rising energy costs and a projected global fossil fuel shortage has led many cultural institutions to start investigating more significant opportunities for energy savings. For a long time, however, the perceived risk to collections in the name of sustainability has made many cultural institutions reluctant to implement, or even investigate, energy saving opportunities. But, with cost projections suggesting that almost one third of a cultural institution’s budget in 2019 could be for energy (Rogers 2010), institutions are now more willing to see how they can do better without putting their collections at risk.

In 2009, IPI received a grant from the Institute of Museum and Library Services (IMLS) to fund a four year experiment on whether controlled shut-downs of air handling units (AHUs) could lead to significant energy savings without causing undue risk to the preservation of collections. Currently in its third year, the experiment is being conducted at the Sterling Memorial Library at Yale University in Connecticut, the Library Annex at Cornell University in New York, the main stacks at the Birmingham Alabama Public Library, the Bryant Park Stack Extension at the New York Public Library (NYPL), and the Southern Regional Library Facility and the Young Research Library at the University of California, Los Angeles (UCLA).  Except for Cornell, eight hour shut downs are implemented in the evenings according to each institution’s set schedule. At Cornell one four hour shutdown occurs from 11:00 PM to 3:00 AM and the other from 11:00 AM to 3:00 PM to reduce energy consumption during peak demand and to further their energy savings.

Experimenting with regular shutdowns challenges two significant barriers to energy savings in preservation environments: that collections need to be stored in completely stable “flat line” conditions of 70°F and 50% relative humidity (RH) and that air needs to continually circulate. Despite the widespread popularity of 70/50 there is little supporting evidence that it is an ideal preservation environment for most collection materials. Research conducted by the Image Preservation Institute and others has shown that temperatures cooler than 70°F and lower RH were found to be better in slowing the rate of chemical and mechanical decay in many materials. Most collection materials were also found to handle short term changes in their preservation environments. Short term fluctuations in RH between 35-65% were found, for example, to have minimal impact on the preservation quality of artifacts because most materials take a few days to a few weeks to fully equilibrate. Research conducted by Mecklenburg (2007) has also shown that many materials can experience elastic shape changes from 30-60% RH without resulting in permanent mechanical damage.

In regard to the need for circulating air, recent findings suggest that there is little need for “fresh” i.e. conditioned air to be continually supplied to collection spaces either to remove volatile organic compounds (VOC) or for human health. Typical buildup of VOCs in collection spaces is simply not large enough to warrant constant removal. Plus, air handling systems, which often require a small percentage of outside air, may actually introduce VOCs rather than remove them. This small percentage of outside air is regulated for human health but if human occupancy in collection spaces is minimal then health is less of a concern, even less so if shut downs occur at night. As an aside, there are many anecdotal examples of outside air dampers being discovered closed for considerable amounts of time without any detrimental effects occurring to either occupants or collections. In these circumstances, the amount of outside air being brought into the space from opening doors or from leakage was enough to the sustain the spaces and occupants inside.

Letting conditions “drift” in a collection environment for the period of a 4 to 8 hour shutdown have revealed at least three pivotal findings thus far (Linden, 2012). First, conditions in  collection environments do not significantly change during an 8 hour shutdown even in hotter climates like at  Birmingham AL. At most, there is typically a 1° to 4°F rise in temperature and minimal fluctuation in relative humidity (primarily due to temperature changes). Second, Time Weighted Preservation Index™ (TWPI) values which are used to assess the quality of the preservation environment, show that the experiment has little negative impact on the preservation quality of the collections involved. Third, concerns that a shutdown schedule will cause wear or breakdowns of mechanical systems have so far not been observed. Many systems are fitted with a Variable Frequency Drive (VFD) which is capable of producing a “soft start” and there is little evidence that the system needs to work harder to compensate for any gain in heat load in the space. Moreover, given how little heat is actually gained during a shutdown, the energy savings lost by the system trying to compensate for this gain in the space is minimal and certainly not enough to discourage using shutdowns for energy savings.


Temperature data from a collection space during an 8 hour nightly shutdown. Temperatures in the space increase by approximately 2 degrees F and then recover to predetermined set point once the system is turned back on.


The experiment being conducted is not a unique application of the use of shutdowns for energy savings. Indeed many institutions have long established shutdown or setback schedules but few have ventured to use them in their collection spaces or for substantial periods of time. Two significant exceptions are the Library of Congress and the Folger Shakespeare Library who have implemented risk-managed shutdowns in specially selected units and spaces in an effort to cut back on energy consumption. In these closely monitored projects, which were undertaken in consultation with IPI, the process of implementing a shutdown identified further optimization opportunities within the system and other units where setbacks or shutdowns could also be applied. The success of these optimization programs, along with those underway at Yale, Cornell, UCLA, NYPL and Birmingham Public Library, have reinforced the notion that closely monitored shutdowns can be applied to preservation environments without causing undue risk to collections. If done correctly, an 8 hour shutdown can effectively reduce energy costs by as much as one third with little to no negative impact on collections.



Jeremy Linden, James Reilly, Peter Herzog, (2012), Research on energy savings opportunities in university libraries, Library Hi Tech, Vol. 30 Iss: 3 pp. 384 – 396.

Mecklenburg, M. F. (2007), Determining the acceptable ranges of relative humidity and temperature in museums and galleries, Smithsonian Museum Conservation Institute

Rogers, M. (2010), Untitled Presentation, presented at Rethinking the Museum Climate Conference, 12-13 April 2010, Museum of Fine Arts, Boston, Boston, MA