Environment

After having advised a museum to aim for a moderate general climate
with no air conditioning in their exhibition and storage areas, we
were asked to define limits for the daily fluctuation in temperature
and relative humidity. We understand that there is a common
agreement, that the amplitude should not exceed 3-5% for relative
humidity and 2-3 deg. C for temperature in a day. But we are not
sure whether this is meant to be an average value over the whole day
or a real max. fluctuation, and if so: in what time period should
this real fluctuation occur?

And what about aerating rooms under these settings? A short aerating
may change the climate considerably within a few minutes, often more
than these above mentioned values as far as conditions in the *room*
are concerned (e.g. in winter dropping of rh and t). After a short
aerating process (several minutes) the room climate recovers within
a short period (e.g. 30 minutes). Has any research been done on the
impact of such an aerating and its change in climate on *objects*
placed in a room, and on interiors in historic buildings? Are a few
minutes of aerating (with the rather fast change of room conditions)
long enough for materials to react/change?  Are there damages
reported caused by intensive aerating (several windows opened) for a
*short* period (some minutes)?

If no damages are reported, would this suggest that the quite narrow
fluctuation limits need further explanations (like in what
time/exceptions etc)? Has anybody already established such less
narrow guidelines for non- climate-controlled areas? We are looking
forward to your comments.

Karin von Lerber and Joachim Huber
Prevart GmbH - Konzepte fur die Kulturgutererhaltung
Oberseenerstrasse 93
CH-8405 Winterthur
+41 52 233 12 54
Fax: +41 52 233 12 57


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                  Conservation DistList Instance 15:37
                 Distributed: Monday, November 12, 2001
                       Message Id: cdl-15-37-011
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