Kristin,
I am in charge of preventive conservation at the Shelburne Museum in
Vermont and have worked with HVAC systems in historic and reproduction
buildings for the past 20 years. Of our 27 buildings that house
collections, 6 have complete HVAC systems, 2 have modified HVAC systems
with humidistatic heating and air conditioning, 3 have only humidistatic
heating and ventilation, 8 have humidistatically controlled ventilation,
1 has only heating, and 7 have no systems at all. My point is that each
building is unique, as are the collections it contains. With
environmental control especially, one size does not fit all. Although
there are still several buildings that require environmental
improvements, we are pleased with the systems we have, their operation,
and the climates they maintain.
Designing a system that is appropriate for the building and the
collections it contains takes prior planning to include a full year of
monitoring to determine existing conditions. It is also important to
consult with a conservator to determine the needs of the collections as
well as HVAC engineers with experience designing HVAC systems for
historic house museums who can advise on what type of conditions the
buildings can support. Historic houses can seldom support HVAC systems
that can regularly maintain "ideal" museum conditions of 68 degrees F
and 50%RH, nor do they have to. Research over the last decade has
indicated that most artifacts housed in historic buildings can be safe
in RH conditions of 35% to 65% and an even wider range of temperatures
if the environmental changes are gradual with the seasons and reasonable
precautions are taken when conditions are at the lower and higher RH
levels. Of course, there are some artifacts that do require more
stringent conditions. A conservator can identify such artifacts and help
design micro-environments or rotation schedules that would keep such
artifacts safe.
Some quick tips on environmental improvements:
1. Use common sense and practical methods to improve environmental
conditions. For example, be sure to use gutters and proper drainage to
move water away from buildings instead of designing oversized systems to
try to dehumidify a building made damp by poor drainage.
2. Work with nature, not against it. For example, consider reducing
temperatures rather than adding humidity to maintain safe RH levels in
buildings in temperate climates during the winter. From my experience,
humidifiers are the most maintenance-intensive pieces of equipment in an
HVAC system.
3. Keep the systems as simple as possible. Consult with a conservator
to see what temperature and RH levels your collections require and
design a system mainly to mitigate unacceptable conditions identified by
the year-long survey.
4. Continue monitoring temperature and humidity after the system is up
and running so that you know when it is working and when it is not.
5. Allow several months to bring the system on-line and trouble-shoot
initial problems. Pay particular attention at the beginning of each
season when heating, humidification, or cooling starts up after being
off for several months.
6. Regular preventive maintenance and responsive repair service is
essential for the equipment and the controls. Contract with a reputable
HVAC contractor, preferably the one who installed the system.
7. One person on staff should be in charge of monitoring conditions,
understanding the equipment and system, and contacting the maintenance
contractor when required.
HVAC systems can be problematic, especially if they are installed by an
HVAC contractor who is a board member's brother-in-law who has never
designed or installed a museum HVAC system, and then ignored. However,
if thoughtfully and properly designed, they can work well with a
reasonable amount of effort.
As David Harvey mentioned, both IMLS and NEH provide grants to
establish monitoring programs, plan and design environmental improvement
systems, and to purchase and install properly designed HVAC systems.
For more detailed information on practical climate control, see the
following articles. If you cannot find the publications, contact me and
I will send copies by email:
"A Practical Approach to Environmental Requirements for Collections in
Historic Buildings," by Richard L. Kerschner, Journal of the American
Institute for Conservation, Spring 1992, Volume 31, Number 1, pp.
65-76.
(available on line at
http://aic.stanford.edu/jaic/articles/jaic31-01-008_indx.html )
"Implementation of Practical Climate Control Strategies at the
Shelburne Museum," by Richard L Kerschner in The Conservation of
Heritage Interiors, Preprints of a Conference, Symposium 2000, Ottawa
Canada, May 17-20, 2000, pp. 161-166.
Richard L. Kerschner
Director of Preservation and Conservation
Shelburne Museum
PO Box 10, Route 7
Shelburne, VT 05482
802 985-3348 Ext 3361
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