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Subject: Environment in historic house

Environment in historic house

From: Barbara Appelbaum <aandh>
Date: Friday, December 29, 2000
Christine Cross <ccross1 [at] execpc__com> writes

>I am currently working on the restoration of a 1930s home in
>Wisconsin, USA. We have recently upgraded the existing HVAC system.
>My question concerns RH levels. I had always been told that optimum
>RH in a historic house was 50% with a temperature between 65 and 70
>degrees Fahrenheit year round. The project architect feels this RH is
>too high and will infiltrate the plaster and begin to rot the wall
>studs. What should we do? Any suggestions for sources concerning
>this topic?

Your architect is correct, that RH levels as high as 50% can be very
damaging to historic structures.  In addition, 50% is not necessary
for preservation of most collections.  RH and temperature levels
need to be set based on the recommendations of a conservator who has
examined the collections and a professional trained in architectural
preservation who can analyze the structure of the building. Together
with staff, and with consideration of local weather patterns and
other matters outlined in the New Orleans Charter, like the ability
of the institution to maintain and adjust the mechanical systems,
they can set realistic levels.

We suggest you go to the Association for Preservation Technology web
site (<URL:>) for the New Orleans Charter. Also,
APT Bulletin 27 (1998) 27-29, an article by us on the team approach
and articles in the Conservation of Heritage Interiors from a
Canadian Conservation Institute conference in 2000.

These issues have been discussed at great length over at least  the
past decade in the professional literature and in a number of
symposia sponsored by APT and AIC.  Please feel free to contact us
directly if we can be of help.

Barbara Appelbaum and Paul Himmelstein

                  Conservation DistList Instance 14:36
                Distributed: Wednesday, January 3, 2001
                       Message Id: cdl-14-36-002
Received on Friday, 29 December, 2000

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