Charlene,
I was at the Smithsonian at the
same time as Marion Mecklenburg, and his work is exceptionally important.
It established that the tight specifications promoted by many museum texts were
not only unnecessary, but they were also unachievable for most situations.
So let's get back to your situation.
If you have a suspended ceiling,
you are lucky - you can lift up a tile and see what is going on. That sure
beats having to cut holes in your ceiling!! 65 degrees for Syracuse is
plenty cold to cause condensation. I have been working with an
internationally-significant historic house museum in the Hartford area (who's
name shall remain confidential unless they want to self-identify) where the
temperatures are not nearly that cold and they have clear evidence of
condensation on the ducts and water staining the ceiling and even
dripping. The colder the T setting, the longer the system has to run to
achieve that setting. And without doubt you will hit the dew point for air
in your space on the ducts, which easily could be as cold as the 40-degrees
range on the duct surface. Even the 50s would probably be below the dew
point during the summer in Syracuse, so anything lower than this, depending upon
the specific day, would result in condensation.
What is of high importance is
how you are controlling the RH. At the afore-mentioned museum in Hartford,
they do not have discrete RH control. The dim-witted engineer who designed
their system roughly 12 years ago (the problem building is "new" and was built
then) thought A/C alone would deal with RH control as a by-product of
temperature control. It did not, and they have mold growing all over on
their collections. HVAC engineers generally are not trained or experienced
in RH control. Or they just do not care. I hope the former.
Everything HVAC is about human comfort. It is not about object "comfort."
Humans are very sensitive to temperature, and much less to RH, so pretty much
all of HVAC control is about temperature. Objects in general are more
sensitive to RH and less so to temperature. Of course, high temperatures
can accelerate degradation processes for many types of materials, but when
looking at a mixed-media collection, a balance of preservation, human issues,
and perhaps money? are involved. In an ideal world, we would keep all
collections at perhaps 40 degrees F and 45% RH year round. But this is not
feasible technically (OK, it is but would be really expensive), not financially
feasible, or would not be satisfactory to humans. While as a conservator,
I would love for a museum to be 40 degrees, can you imagine the complaints, not
just from visitors, but from tour guides or docents or staff, who generally are
the biggest problem. They don't care two toots if the collections are
happier if they are cold. And please understand I personally hate to be
cold, even more so than being too warm, so I am not criticizing anyone, just
pointing out the contradictions in the needs for collections and for
people.
So as a conservator with many
years of experience in dealing with creating the best possible compromise for
collections that do not have a boatload of money, I would make the following
suggestions. 1) As soon as possible begin monitoring your environment with
data loggers. Do not rely on info from the HVAC system - it may not be
accurate for the specific location of objects in your room. 2) Understand
the basics of T and RH. Near the floor will ALWAYS have higher RH than
near the ceiling - Ts are higher at the ceiling and since the absolute amount of
moisture in the air is the same in the room, warmer Ts at the ceiling mean the
RH is lower; cooler Ts at the floor mean the RH is higher. This is
straight, plain physics. If the air circulation is high and temperature
stratification does not exist (I don't believe I have ever seen this in a
museum), then the RH at the floor may be the same as at the ceiling, but only if
the T is the same. 3) If you have true RH control, which I really hope you
do, but seriously doubt you do, I would set the T in the general 75 degree level
in the summer while keeping the RH at about 45%. If you can do this,
wonderful! 4) I would gradually let the T creep down with the seasonal
change, certainly as low as 45 degrees in the dead of winter. And I would
try to keep the RH up at 45%, although I doubt you will be able to do so.
The colder you keep it, the easier it will be to keep the RH up. If this
truly is a storage room only, you may be able to do this. But if people
will be in there, expect complaints and you may have to make alterations due to
human issues. These suggestions will save you money both in the summer and
the winter. And if you do not have to pay your own utilities, it will save
energy, reduce pollution, and reduce global warming. All are
wins.
This is much more complicated
than I have presented, but I am trying to simplify it as much as possible.
Yes, I understand that I may have overlooked a few things, but for the potential
"haters" out there, please understand that saying "you must contact a
conservator or informed HVAC engineer" simply is not possible for a lot of
institutions. I wish it were not so, but it is. So, we try our
best. Thank you.
By the way, there is a GREAT
preservation architect in Syracuse who may be able to help you, and I would be
happy to provide his name if you contact me privately.
Marc
American Conservation Consortium, Ltd.
4
Rockville Road
Broad Brook, CT
06016
www.conservator.com
860-386-6058
Marc A. Williams, President
MS in Art
Conservation, Winterthur Museum Program
Former Chief
Wooden Objects Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
From: [log in to unmask]
href="wlmailhtml:{658C61D6-8DA7-483D-9669-08180ECC619D}mid://00000299/!x-usc:mailto:[log in to unmask]">charlene
martin
Sent: Tuesday, August 25, 2015 12:10 PM
Subject: Re: [MUSEUM-L] HVAC settings for mixed collection storage
rooms
Thank you for the reply - I have
definitely added more info, so please reply with further
advice!
My archive storage rm is
located in Syracuse NY, within a mixed use office floor. Is 65 degrees
is too cold for the summer? What is the ideal seasonal drift rate for
summer in Syracuse NY, for both temp and RH?
We just moved in 2 wks
ago. I designed the archival storage room as a preservation space, but have
found some specifications were compromised. As a result, I have a
suspended (drop) ceiling made of tiles of some corrugated-type material, set on
a grid.
The moisture is showing up in the form of rust-colored spots on
the tile (please see pic).I do not have a schematic of the ductwork in the
ceiling (am working on getting that from the facilities manager), but I suspect
that pipes are indeed "sweating".