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Subject: Vapor barriers

Vapor barriers

From: Paul Himmelstein <aandh>
Date: Friday, September 15, 1995
Michael Knies's request for information re: vapor barriers raises
several issues. Clearly the choice of material is not the most
pressing question. The architects' response is a classic one,  and
it should not be up to the institution to specify the type of
barrier;  this is a smoke screen. Several issues must be settled
before a vapor barrier can be specified. Among these are: what RH
will be maintained in the winter,  what are the insulating
properties of the existing and new building materials, what is the
outside RH and T in the winter.

An HVAC engineer with experience in this matter should be part of
the design team.  A conservator should also be consulted when the RH
specifications are formulated.  Much will depend on the type of
collection, and the needs of specific parts or objects in the
collection. It seems likely that installing a barrier with the type
of construction described will be almost useless. With studs
attached directly to an outside wall, the temperature of the barrier
is likely to reach down to a point where condensation will occur,
exactly what you don't want. While it is nice to see that the need
for a vapor barrier has been acknowledged, it is not right that the
institution has been pushed into a corner.

Paul Himmelstein

                  Conservation DistList Instance 9:27
                Distributed: Tuesday, September 19, 1995
                        Message Id: cdl-9-27-001
Received on Friday, 15 September, 1995

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