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SAA integrates with ASHRAE.


Timing couldn't be better; the Society of American Archivists (SAA) has been studying the need to establish comprehensive and uniform guidance for the design of archival facilities. A special task force working group Cochaired by Archival Facility Consultants Michelle Pacifico and Thomas Wilsted was created which consisted of representation from the engineering industry, architectural expertise, construction industry, archive users, and expertise of the Library of Congress (LOC) and the National Archives and Records Administration (NARA). The task force has spent about 2 years in its deliberations to develop realistic design guidelines for facilities design and their environmental criteria for temperature, relative humidity and filtration needs.

The fruits of their labors are soon to reach the general public in a new publication which will be a comprehensive guide for archive designers. The document is titled "Archival and Special Collections Facilities Guidelines for Archivists, Librarians, Architects, and Engineers". The document will be available in fall 2009 and is published by the Society of American Archivists. Timing is perfect because ASHRAE is right now in the process of revisiting its handbook chapter which addresses the design of Museums, Galleries, Libraries, and Archives. Accordingly, it looks like the two agencies will be able to be consistent with each other, thus strengthening the value of both ASHRAE and the SAA as their design guidelines go forward in an integrated fashion.


How Did We Get Here Today?

Establishing environmental standards for museums, libraries, and archives has been a long road for both ASHRAE and SAA. It wasn't until the 1999 ASHRAE Handbook--HVAC Applications, Chapter 20, that ASHRAE finally took a hard look at the design of museums and found their engineering design practices throughout the country to be lacking in the underlying need to differentiate a museum from a computer room. Both need precision climate control, but computer rooms have a high sensible heat load from their electrical equipment while museums have a high latent heat load largely from infiltration of unconditioned outdoor air. Some designers were specifying computer room HVAC equipment for use in museums and their archival storage rooms. As a result, some installations were often problematic because the computer room HVAC equipment did not have large enough capacity reheat coils. Thus, on a call for dehumidification by the HVAC equipment's humidity controls, the HVAC unit would continue to cool the room but could not sufficiently reheat it. The result would be a spiral effect of room cooling and relative humidity rising to the point where cooling coils would ice over and high humidities would actually lead to mold outbreaks.

While some designers were specifying computer room HVAC equipment in museums and their storage rooms, some other designers of libraries and archive vaults had little or no published standards or design guidance. As a result, many libraries had been designed mostly as commercial spaces with only temperature controlled HVAC systems that either heated or cooled their rooms during the occupied daytime and shut down or setback at night. While shut down their room conditions would heat up in summer thus lowering their relative humidity, and cool down to set back settings on winter nights. This daily temperature cycling would also create daily substantial relative humidity cycling fluctuations.

Early, in the 1980's the Library of Congress studied the effect of relative humidity fluctuations on the accelerated aging of paper at their Washington D.C. laboratory under the direction of Chandru Shahani (Shahani, Hengemihle, and Weberg undated).

Then in 1994 David Ehardt and Marion Meckenburg of the Conservation Analytical Laboratory of the Smithsonian Institution (Ottawa Congress 1994) presented the results of their formal testing of the behavior of museum collections to changing humidity environments. The research found that large fluctuations of relative humidity should be avoided. The general outcome of this research resulted in a new movement toward producing room environments which focused more on environmental stability. This would require an HVAC system to operate continuously all day and all night.

And so began the trend for libraries to copy this philosophy and operate the HVAC systems for their archives and special collections continuously day and night. However, most of these libraries had HVAC systems which had only basic temperature control and no dehumidification reheat capability. As a result, during the summer season it has been found that these rooms would have relative humidity levels at or above 70% RH continuously from June through August. The result--mold outbreaks!


Finally in 1997 a special subcommittee was created by ASHRAE through its technical committee TC9.8 headed by William Rose et al. to examine the museum failures. The special subcommittee represented all walks of museum expertise including the research work of the Canadian Conservation Institute (Michalski 1993). This special subcommittee implemented a dramatic improvement to the ASHRAE Handbook which until 1995 only contained two pages of general information that addressed museums design. The special subcommittee created a complete new handbook chapter published in the 1999 ASHRAE Handbook--HVAC Applications, Chapter 20 just dedicated to museums, libraries, and archives design. It was a revolutionary step forward for the historic preservation community in the United States.

Again, in the next normal 4 year cycle of review, the 2003 Handbook--HVAC Applications, Chapter 21 further refined and improved these design guidelines. As a result, more information was integrated into the Handbook to help make it more user friendly and energy efficient.


Archive facilities have long been regarded by some designers as either a warehouse or the back storage rooms in a library. However, archive facilities consist of a whole host of building types and spaces. They are storage spaces on the State and Federal level for legal and other government records or local town halls which contain vaults for deeds, tax records, financial data, official meeting records and other vital records.

The various research tests over the last ten years by NARA, LOC, and the Smithsonian Institution, as well as other agencies including The Canadian Conservation Institute have found that dramatic changes in archival records preservation methods are needed. The SAA with input from a variety of sources including the Library of Congress has now produced a unified design guideline for archival facilities of all types. This is a first ever consolidated document to address all the special aspects of archives design. It is titled "Archival and Special Collections Facilities Guidelines for Archivists, Librarians, Architects, and Engineers." It is presently in the final draft review publication stage. Copies can be obtained through the References appendix.


The LOC has largely lead the research field in examining the preservation needs of archival paper documents. In 1995 William Wilson (Wilson 1995) authored the NISO Press "Environmental Guidelines for the Storage of Paper Records" based on the Shahani, et al research efforts at the LOC Washington, D.C. laboratories. The tests found that paper has a lower limit of relative humidity stability of 30% RH. Below this point paper is so brittle that when handled and folded its fibers begin to break. This is irreversible. Therefore, the LOC set the lower limit of relative humidity to be 30% RH for archival preservation. The LOC and Wilson's research also studied the combined effects of temperature and relative humidity on paper archive collections aging.

Arrhenius equations were used along with the laboratory accelerated aging tests. The Arrhenius equation is named after Svante Arrhenius who identified the relationship of temperature to the rate of a chemical reaction in 1889. J.J. Hood then formulated the relationship into a mathematical equation to accurately express the findings of Arrhenius. The Arrhenius equation has become widely used as an accurate tool to predict the rates of decay do to physical and chemical aging. By extrapolation from the work of Graminski (Graminski et al. 1979) and Erhardt (1995), a table is presented in the NISO Technical Report TR01-1995 that shows the relative reaction (degradation) rates of paper at various temperature and relative humidity conditions based on the rate of paper degradation at 70[degrees]F (21 [degrees]C) and 50% RH being 1.00. In general, the table shows that the cooler and dryer, the better for preservation.

Given the current practical state of the art of HVAC equipment, the choice of minimum temperature for maximum preservation was concluded to be 50[degrees]F (10[degrees]C) at a relative humidity of 30% RH for archival preservation.


The maximum preservation philosophy of 50[degrees]F (10[degrees]C) and 30% RH is considered the ultimate environment for archival preservation. However, given the new generation of HVAC equipment by manufacturers needing to meet new U.S. Green Building Council (USGBC) and ASHRAE Standard 90.1 HVAC energy efficiency demands, SAA has re-examined the viability of preservation of important records by agencies mandated to preserve records indefinitely.

Using the Arrhenius equations of deterioration, it was found that the deterioration rate of paper kept at 50[degrees]F (10[degrees]C) and 30% RH or slightly elevated to 60[degrees]F (15[degrees]C) and 40% RH was insignificant for most paper materials when compared to environments in unconditioned storage vaults in basements and attic spaces. In addition, the present HVAC equipment market place now has excellent equipment that can produce these environments of 60[degrees]F (15[degrees]C) and 30% to 50% RH at a reasonable operating cost. Examples of these systems include hot gas reheat air handlers (Figure 1); traditional climate control air handlers with low temperature glycol chilled water and waste process hot water reheat (Figure 2); and packaged energy recovery air handlers which use heat recovery or enthalpy energy recovery wheels (Figure 3).





It is now proposed that ASHRAE adopt the same environmental standards as SAA has promulgated in its newly released design guide.

These are as follows:
Maximum best storage         50[degrees]F (10[degrees]C)  30% RH
Permanent archival storage   60[degrees]F (15[degrees]C)  40% RH
Occupied archives            68[degrees]F (20[degrees]C)  50% RH
Open reading areas           70[degrees]F (21[degrees]C)  55% RH

Seasonal drift to reduce energy costs in heating climates is acceptable so long as the change is gradual. Therefore, slowly changing the settings for permanent archive storage from 60[degrees]F (15[degrees]C) and 30% RH in winter to 60[degrees]F (15[degrees]C) and 50% RH in summer is a valid design and operating approach. The generally accepted day to day overall tolerance of fluctuations is [+ or -]2[degrees]F ([+ or -]1[degrees]C) and [+ or -]5% RH for paper based records.


We need to thank the USGBC for the pressure they have put on the HVAC industry to develop energy efficient equipment and HVAC equipment which can economically dehumidify using the refrigerant process hot gases which are "free" and the use of heat recovery wheels to recover wasted heat energy. These devices can produce cooling down to 60[degrees]F (15[degrees]C) and 50% RH during summer and up to 60[degrees]F (15[degrees]C) and 30% RH during winter in most heating climates of the United States. There are now numerous manufacturers which can offer this equipment.


Erhardt, D. and M.F. Mecklenburg. 1994. Relative humidity rexamined. 11C Ottawa Congress. A. Roy and P. Smith, eds. London: International Institute for Conservation of Historic and Artistic Works.

Graminski, E.L., E.J. Parks, and E.E. Toth. 1979. The effects of temperature and moisture on the accelerated aging of paper. In Durability of Maccromolecular Materials. Washington, D.C.: American Chemical Society, pp. 341-355.

Michalski, S. 1993. Relative humidity: a discussion of correct/incorrect values. ICOM Committee for Conservation 10th Triennial Meeting, Washington, D.C.

Wilson, W.K. 1995. Environmental guidelines for the storage of paper records. NISO Technical Report: 1, NISO-TR01-1995. NISO Press, Bethesda, MD.

Wilsted, T.P. 2007. Planning new and remodeled archive facilities. The Society of American Archivists, Chicago, IL.

Wilsted, T.P. and M. Pacifico, eds. 2009. Archival and special collections facilities; Guidelines for archivists, librarians, architects, and engineers. Society of American Archivists, Product code: BOOKSAA-0538.

Ernest A. Conrad is a principal with Landmark Facilities Group, Inc., Norwalk, CT.
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Title Annotation:Society of American Archivists and American Society of Heating, Refrigerating and Air-Conditioning Engineers
Author:Conrad, Ernest A.
Publication:ASHRAE Transactions
Geographic Code:1USA
Date:Jan 1, 2010
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