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Subject: Environment in historic house

Environment in historic house

From: Will Jeffers <wjeffers>
Date: Tuesday, December 26, 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?

I would advise against trying to maintain 50% RH in the winter
months.  While the HVAC system may have the required capacity to
maintain this level, it will be detrimental to the structure unless
an adequate vapor barrier has been installed.

While there are dissenting opinions within the field of preservation
on appropriate temperature and relative humidity standards for
preservation, I believe everyone is in agreement that there is no
use in humidifying a structure beyond the effective limits of its
vapor barriers.

Will Jeffers
Collections Care Specialist
Department of Scientific Research
Museum of Fine Arts
465 Huntington Avenue
Boston, MA 02115
Fax: 617-369-3702

                  Conservation DistList Instance 14:36
                Distributed: Wednesday, January 3, 2001
                       Message Id: cdl-14-36-004
Received on Tuesday, 26 December, 2000

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