The distribution list known as Conservation Distlist could probably
better help you out with you RH problem. The list is comprised of
professional conservators and individuals associated with the field of
conservation. Information on subscribing to the list can be found at
Conservation Online:
(http:/www.palimpsest.standford.edu). If you don't wish to participate
on the list personally perhaps someone you know who is already involved
on the list can post on behalf of you. Responses can be directed to your
personal email address.

Andrea Reichert
Curatorial Assistant
Manitoba Craft Museum and Library

> I apologize many times over for the length of this post! I am looking
> for advise on a series of problems with our collection storage that
> are interrelated. First, a little background to explain the structure.
> The Museum is a 1936 replica of a stone house which stood in
> Nacogdoches, Texas from circa 1790 until 1902. The desire in 1936 to
> replicate a stone house that the town felt remorseful for having
> demolished has led to no end of trouble trying to fulfill their other
> goal of starting a museum. (I don't know which goal was on first.) The
> Museum's collection storage is a second floor room built in 1991 as a
> "lean-to" addition to the 1936 stone structure designed to look like a > lean-to added to the original house somewhere around 1850. The
> downstairs area is an office space. The collection space is generally
> 15 by 40 ft.  Access to storage is limited to one oak door at top of
> wooden stairs that also lead into the upstairs gallery of the stone
> house. The space has its own HVAC unit but no humidistat at the
> moment. The RH was consistently 55% for three years, then dramatically
> rose to 70 one year. I have dehumidifiers cranking non-stop to keep it > below 65 now. (The humidity in the the stone structure has never
> changed from 55.) We have isolated some of the causes, but not all.
> The back of the HVAC closet return air space, which backs up to the
> stone wall of the 1936 structure, is not closed. In other words, we
> can see stone. The upper portion of the closet has a sheetrock wall,
> but the return air portion was left unfinished. We found insulation
> stuffed into the area which had become saturated and had fallen down.
> The addition has a continuous roofline from the stone structure. But
> apparently, the stud wall connected to the stone structure has no
> exterior, so that behind the sheetrock in the collection room is
> stone. The exterior of the addition is board and batten with the walls
> connecting to the stone building shaped to fit the stone but the ends > are unsealed. The HVAC unit is too large for the space, I'm told, so
> it rarely runs. Will a humdistat solve this problem? Does the open
> space between the addition and the stone house mean moisture can
> migrate not only through the gaping hole in the HVAC closet, but also
> through the sheetrock wall?  Is there some sort of sealant or other
> process to mitigate the problem?  A review by the fire marshall
> suggested a second access to the storage by adding a window large
> enough to remove collection pieces if the stairs are no longer
> accessible. Another suggestion was a steel door and frame to further
> isolate the collection room from the remainder of the building. At the > moment the collection room has strong security and I'm relunctant to
> install a window in the space. The window can be shuttered, as most of > ours are already, and I can add other security measures to tie into
> the existing security system. I need to balance security, fire
> prevention and response, and humidity control. I have money right now > to implement the window door and repair to the HVAC closet. I don't
> know what to do, if anything, about the flow of air between the
> addition and the stone structure.
>
> I thank you in advance for your patience in reading this far, and for your advice.