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For the purpose of this bibliography, practical climate control is described as alternative strategies to standard heating, venting, and air conditioning, or a modification in the design or use of standard HVAC systems to improve museum environments. Until the early 1980's, there was limited discussion of methods to improve environmental conditions other than complete climate control, since complete systems were required to achieve the recommended conditions of 48%52% RH and 6568°F. Since such systems were expensive and difficult to install in historic buildings and expensive to operate, few small and mid-sized museums were able to improve environmental conditions for their collections. In addition, maintenance of the recommended conditions could cause serious damage to historic buildings in temperate climates.
During the mid 1980's, several U.S. conservators and engineers initiated a different approach to environmental control. They began to investigate simpler, low cost methods for improving collection environments. Adopting methods developed in Canada and the United Kingdom during the 1970's, their goal was not to achieve a "perfect" climate, but rather to improve existing conditions by allowing temperature and relative humidity levels to float seasonally within broader limits while limiting temperature and RH extremes. This holistic approach led to the investigation of practical climate control measures such as minimal heating during winter months to avoid drying out artifacts and buildings, humidistatically-controlled heating to prevent high humidity levels during cool rainy periods, and humidistatically-controlled ventilation to decrease humidity and heat buildup in collection buildings during hot and humid weather. In addition, efforts were made to control problems at the source: direct water away from buildings by improving building and ground drainage systems, control dust on paths and roadways throughout the site, change programing so that historic buildings would not have to be heated and desiccated during the coldest winter months. For a more complete explanation of practical climate control measures, read Kerschner's article referenced in the bibliography.
In the early 1990's, the development of practical climate control methods was aided by two actions. (1) the National Endowment for the Humanities established the Division of Preservation and Access and began awarding grants of up to $1 million to improve collection environments. The NEH recognized that practical climate control methods were cost effective and had a potential to significantly improve environmental conditions for material culture artifacts. (2) The Smithsonian's Conservation Analytical Laboratory published research that indicated that relative humidity standards broader than 48%52% were safe for many materials. Although broader standards had been proposed by other conservators as early as 1964, CAL's often-challenged claim that museum's could save significant amounts of money by designing environmental improvement systems to the "new" standards caught the attention of large and small museums throughout the U.S and heightened interest in practical climate control methods.
1. This bibliography is presented in a non-standard format to simplify use. The five books that offer significant practical climate control advice are listed together under Books at the beginning of the bibliography. Tim Padfield's electronic book being written on his home page on the Internet is an interesting and helpful addition to the traditional publications. Twenty-five of the most pertinent papers are published in two IIC, and one ICOM conference preprints, and an APT publication of two related conferences. These Conference Proceedings are grouped in a separate section. The Articles section follows a conventional bibliography format.
2. Although this bibliography was compiled during the investigation of environmental improvement techniques for collections housed in historic structures, some of the articles do not directly apply to historic structures. They are included to promote out-of-box thinking that may eventually lead to solutions for historic, conventional, and new structures. We tried to cover a wide variety of climates. We also included many citations from sources besides conservation and museum literature, in order to highlight relevant material from other disciplines, such as landscaping, weatherization, residential remodeling, etc. As there is disagreement both within and outside the conservation community regarding both standards and treatments of historic structures, some of the citations directly contradict each other. These conflictiong opinions were deliberately included to promote further discussion about these issues amongst conservation professionals.
3. The safety of collection artifacts exhibited and stored in environments maintained by practical climate control methods is paramount. Therefore, a few seminal articles explaining the rational for broader humidity standards and the possible effects on materials are included in this bibliography.
4. Although practical climate control measures can create an environment that is safe for a majority of collection materials, there will be some materials that require more stringent relative humidity and temperature conditions. The use of micro-environments to protect such artifacts is an integral part of practical climate control. Since several bibliographies on micro-environments exist, only three representative articles discussing different aspects of micro-environments are included in this bibliography.
5. For additional references related to practical climate control methods, environmental standards, and micro-environments, refer to the "References" sections at the back of each book or article cited in this bibliography.
As stated in the introduction, this book "presents a strategic approach to environmental management, in contrast to the piecemeal approach to environmental monitoring and control still practiced by many museums. However, rather than providing ready solutions and rigid rules, the book introduces principles and ideas on which to base decisions about creating the right environment." Ms. Cassar addresses high-tech and low-tech issues in an easily understood format.
A collections of papers discussing energy efficiency in museums. Some of the energy-saving techniques such as tightening the building envelope and properly insulating a building are also applicable to practical climate control strategies.
This is an excellent book on environmental standards and HVAC and other preventive conservation equipment used in libraries and museums. The seventh chapter on "Interim and Low-cost Environmental Improvements" provides detailed advice on the proper installation and use of: humidifiers, dehumidifiers, and filtration systems; reduced heating and humidistatically-controlled heating; and other practical climate control measures.
This book in progress, also referred to by Padfield as a tutorial on museum climate, already contains over 20 chapters addressing subjects such as "Condensation in the walls of humidified museums," and "Humidity buffering by museum walls." Other chapters are sure to foster creative thinking about museum environments. Padfield also offers to answer readers' questions by e-mail.
In preparation for adding a new wing to the museum building, the ROM established temperature and relative humidity "Categories of Sensitivity" for museum artifacts based on the sensitivity of the materials from which the artifacts were made. An early attempt to systematically establish realistic, attainable RH standards for different types of objects. Includes an annotated bibliography on museum environments.
The following four papers are selected from the above publication:
A very informative article detailing the successful use of freestanding humidifiers and dehumidifiers, and ventilation through fireplace flues to reduce and stabilize RH levels, reduce carbon dioxide levels, and improve visitor comfort in art galleries in a large historic building in London. A computerized BMS (building management system) is essential in controlling the numerous pieces of equipment dispersed throughout the galleries.
A Swedish-Danish research and development collaboration was established to develop a resource-saving concept for the establishment of a climate suitable for the storage of objects using natural climate control. The state archives of Schleswig-Holstein is cited as a storage facility that maintains an almost constant relative humidity in a heated, well-insulated, unventilated room buffered by the archives themselves.
The evaluation of the interior climate of a church built in 1100 near Copenhagen leads to the conclusion that a modern museum building built with porous outside walls of light weight concrete may result in a stable relative humidity-buffered climate that could maintain safe relative humidity levels even in cold winter climates by allowing water vapor to diffuse into the building through porous floors. An interesting article challenging the traditional construction methods of impermeable walls with interior vapor barriers for museum buildings in cold climates.
An excellent, understandable, detailed explanation of what RH levels are safe and what are not for a variety of materials. Safe RH for an object depends on the material from which the object is made and how it is constructed and is more of a "broad valley" between 35% and 60% than a close tolerance around a specified value. (This article was selected to represent the numerous articles addressing the continuing debate over appropriate relative humidity standards for museums.)
The following five papers are selected from the above publication:
This paper summarizes the historical development of heating methods in Austria, experiences with different heating systems, damages caused by heating, and related economic aspects. The authors make recommendations for safe heating levels in historic buildings in Austria.
Environmental improvement measures sympathetic to two English historic homes are discussed. A variety of different types of heating, humidification and dehumidification systems are discussed to mitigate the worst environmental conditions without seriously compromising the historic building fabric.
A well-reasoned and eloquent call for realistic and practical climate control standards.
A good summary of how buildings work, providing essential background information for understanding how to control heat and moisture in historic buildings and how to ventilate them.
A standard discussion of possibilities and problems with "climate control, the elimination of really dangerous conditions without attempting the constant climate theoretically possible with ducted air conditioning." (from paper's introduction).
The following eight papers are selected from the above publication:
A candid discussion of the wide range of environmental conditions that objects on loan are probably exposed to and the damage that does or does not occur as a result of environmental changes.
Important information on the difficulty of measuring relative humidity to 50% + or -5%.
This paper presents results of materials research on museum objects conducted by the authors that leads them to the conclusion that many museum artifacts can safely withstand wider fluctuations in relative humidity than previously accepted by many conservators. The publication of this paper, and the claim by the authors that adoption of these more liberal relative humidity limits could save museums significant amounts of money, resulted in the re-examination and evaluation of RH standards that continues today. These more liberal RH guidelines are important for museums in historic buildings who plan to implement practical climate control concepts.
A new archives building in England is specifically designed to utilize the thermal mass of the structure and the RH buffering capacity of the storage stacks as part of passive environmental control for most of the building. The temperature and humidity in the archives vary seasonally, but daily fluctuations are kept to a minimum. A small air-conditioning plant serves the reading room.
The aim of this project was to improve conditions for painted objects in wooden churches in Norway, based on the premise that the natural climate (cold in the winter) is better for painted wooden objects and for the church structure than the artificially dry climate produced by heating. Methods of providing localized heat for the comfort of occasional worshippers without heating the entire structure are discussed.
Using data from six air-conditioned and non air-conditioned historic house museums in the south of England, the authors found that air conditioning does not always provide tight control or a more stable environment. It is suggested that more study is necessary to quantify the effects of passive climate control measures such as the use of heavy building construction, hygroscopic materials, and thermal buffering.
This article presents an excellent summary of practical climate control methods used in England. Topics discussed include conservation heating to maintain as constant a relative humidity level as possible, dehumidification of sealed storage areas with stand-alone dehumidifiers, digital control of user-friendly environmental equipment, and staff training in operation and maintenance of equipment. The National Trust Specification for Conservation Climate Control is presented as an appendix.
This paper suggests wider RH standards and a controlled seasonal RH fluctuation for historic house museums in the U.S. as a compromise for the long-term preservation of both the buildings and the collections they contain.
This entire issue is devoted to proceedings of two symposiums on museums in historic buildings held in 1990 in Montreal and 1991 in New Orleans. It includes eight papers relevant to practical climate control and the New Orleans Charter, a document written in 1991 presenting "principalsgoverning the preservation of historic structures and the artifacts housed in them." Of particular interest is Dennis Brown's article "Alternatives to Modern Air-Conditioning Systems: Using Natural Ventilation and Other Techniques."
Homeowners add shade trees, plants, and trellises outside their desert home, increase insulation, double glaze south facing windows, and install a fan to move air inside their home. These changes allow significant reduction in air conditioner use.
These articles contain timely general advice for historic house museums and new museums even though they were written more than 30 years ago. Buck issues an early call for broader relative humidity standards of 55% + or 10% and provides a table that predicts the effects of RH levels at these extremes on various materials. Amdur's proposal for a room-within-a-room offers a solution to the problems encountered with humidifying older buildings without vapor barriers during cold winter months.
The author discusses how the degree of climate control within a case is influenced by the construction parameters of the case. A matrix is used to consider 20 different case configurations and specific examples are cited. (A summarizing work chosen as representative of the many articles on micro-environments.)
Much can be learned about mitigating high interior temperatures in hot, arid Saudi Arabia by studying traditional indigenous design and construction materials (adobe).
Accurate information on how to safely insulate and ventilate an old house, important practical climate control considerations. The more controlled a given volume of air in a building is, the easier it is to maintain a constant RH and buffer against daily fluctuations.
Routine description of temperature and relative humidity requirements, instrumentation to measure and record RH and temperature, and mechanical equipment to maintain conditions. Informative, but nothing new or innovative.
The "user-friendly" approach focuses on measuring pressures rather than just leakage to help determine which weatherization treatments a building needs. The author describes how a blower-door unit is used to depressurize a building and find leaks in the thermal and pressure boundaries for air-sealing.
The author briefly addresses the possibility of operating HVAC systems on low capacity or not at all during unoccupied hours for areas of the museum that contain artifacts resistant to RH and temperature fluctuations. An interesting idea that could work depending on the buffering capacity of the building and collections. Significant monetary savings could be realized, but the safety of the artifacts must come first.
A new less invasive way to install central air conditioning in a historic house is presented. Traditional air-conditioning equipment, heat pumps, and ductless air conditioners are explained.
An excellent article explaining how air and vapor barriers work. Most useful for new construction, but important to understanding why a historic building without vapor and air barriers could be harmed by high RH. Explains how use of air and vapor barriers in hot and humid climates is different than in temperate climates.
A holistic approach to environmental improvement that considers preservation of the buildings and the artifacts they contain. Categorization of historic buildings as to their potential for environmental control is recommended. Seven practical climate control options are detailed. Understandable information for the beginning museum professional.
A seminal article introducing the concept of humidistatically-controlled heating, the maintenance of a relatively stable humidity level within a building by varying the temperature of the air within the building.
The basic equipment and techniques used to identify moisture problems in old buildings are discussed.
Practical advice on determining the thermal boundary of a building and weatherizing a building to reduce outside air infiltration and heat loss. Lugano stresses the importance of a continuous thermal envelope and gives practical advice on how to achieve that in an old house. He also discusses his preference for cellulose insulation, especially using a dense-pack method, in historic structures over fiberglass, which he does not consider as effective or appropriate. (Authors' note: The RH buffering capabilities of dense-pack cellulose is an area that merits further research.)
More practical advice on determining the thermal boundary of a building and weatherizing a building to reduce outside air infiltration and heat loss. The authors define a house as a system, and describe air movement in buildings in an understandable way.
Further development of the humidistatic-heating concept, adding basic ventilation and dehumidification to provide a safe environment for a carriage exhibited in a glass enclosed room. The author also addresses the use of blinds to control sunlight striking the carriage and documents the deleterious effects of moving a carriage from storage in a dark, unheated wooden shed to a modern glass box exhibit room.
An alternative to silica gel is proposed for environmental control of individual or multiple display cases. Another approach to micro-environments as an alternative to whole building environmental control. (This is the representative entry in this bibliography for RH control modules.)
These articles explain how to utilize plantings and building siting to increase energy efficiency in various climates. Practical, cost effective methods to reduce energy loads on buildings are presented. Very applicable to new or modern construction, but less applicable to historic buildings where site landscaping is well established and difficult to alter.
Excellent article comparing three different climate control strategies for three different historic houses: (1) extensive building intervention to install complete HVAC system and vapor barriers, (2) maintain and update marginal equipment and remove artifacts as required, (3) low-level heating and natural ventilation to maintain climate for building that contains few artifacts.
An excellent article that clearly explains conventional environmental systems used in libraries and museums. More importantly, passive climate control methods including building-within-a-building design, landscaping, protective enclosures for books, and temperature and RH buffering capacity of books are addressed in detail. Seasonally adjusted RH ranges of 35% to 62% are recommended for library collections in historic buildings.
A technical explanation of an effective approach to operating an air-conditioning system to maintain the correct water vapor content of the air to hold a specified moisture content in wood, applicable to museum storage rooms containing large amounts of hygroscopic buffering materials such as wood or paper.
This paper emphasizes adoption of the expanded relative humidity range of 40%-65% with gradual seasonal changes to meet the RH requirements of both the historic building and the objects it contains. Buffering effects within historic buildings are briefly discussed.
This general paper for the beginning museum professional addresses a wide range of museum environmental problems from light to pests. The four-page section on temperature and RH outlines several practical climate control strategies applicable to historic house museums.
Micro-environments are not the focus of this bibliography, but any discussion of practical climate control measures must consider the use of micro-environments for artifacts especially susceptible to changes in relative humidity. It explains the design of the basic climate controlled showcase using silica gel. (This article was selected as a representative sample of the use of silica gel to control micro-environments.)
A technical article analyzing how moisture moves through the building envelope. Humidity control that overrides temperature control during periods of extreme outdoor conditions is recommended to stabilize RH levels for collection artifacts.
Practical advice concerning reducing temperature in churches to prevent low relative humidity during cold weather. Twenty organ manufactures generally agree that cold temperatures harm organs less than low relative humidity.
Authors' note: The mandate of the Interfaith Coalition on Energy (ICE) is to reduce energy costs for the approximately 4000 churches in and around Philadelphia. They publish a quarterly newsletter, Comfort and Light, and 22 research reports, several of which are related to practical climate control i.e. "Measurements showing savings from ceramic panel infrared heating." For a list of publications, contact Andrew Rudin, ICE, 7217 Oak Avenue, Melrose Park, PA 19027-3222, ph. (215) 635-1122, e-mail 754-0723@mcimail.com
Construction of a prefab insulated panel storage building for natural history and ethnographic artifacts is presented. Temperature is controlled to 68°F year round and interior RH in this dry region remains steady at 30% with no special equipment. RH levels in similar storage facilities in more temperate areas of the country is not addressed.
This chapter provides a good overview of relative humidity guidelines and various relative humidity control methods, presenting a range of practical methods other than complete HVAC. Information presented would be very useful for small museums and historic houses.
The author evaluates the effects of no ventilation, natural
ventilation, forced ventilation, and evaporative cooling on interior
temperatures in a concrete block desert house.
RICHARD L. KERSCHNER, chief conservator at Shelburne Museum in Vermont established the conservation division of the museum's collection department in 1983 and was appointed to his current post in 1986. He holds an M.A. in conservation from Cooperstown (1982), a B.S. from Bucknell University (1973), and is a fellow of the American Institute for Conservation of Historic and Artistic Works. As a member of the board of directors and head of the collections committee of the Vermont Museum and Gallery Alliance, he guided the creation of the Vermont Collections Care Program. Kerschner is a recognized authority on envrionmental control for collections housed in historic buildings and has lectured widely on practical climate control issues. Address: Shelburne Museum Conservation, P.O. Box 10, Shelburne VT, 05482.
JENNIFER BAKER is a graduate of the Smithsonian Institution's Furniture Conservation Training Program, and has a BFA from Boston University. She is a Professional Associate of AIC. She maintains a private practice in the conservation of furniture and wooden artifacts, and consults on conservation concerns in museum and exhibit design. Address: 277 Pine St., suite 5, Burlington, VT 05401. email: jdbaker@together.net
The compilation of this bibliography was supported by the Getty Conservation Institute.