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]">charlene martin

Sent: Tuesday, August 25, 2015 12:10 PM

To: [log in to unmask]">[log in to unmask]

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".

On Tue, Aug 25, 2015 at 11:25 AM, Marc A Williams <[log in to unmask]> wrote:

Where is your facility/museum located (town, state)?  That may make a difference in the recommendation.  65 degrees is really cold for the summer.  Depending upon your specific situation and lay-out of HVAC equipment & duct work, I would guess that you are getting condensation on the ductwork, which is causing the ceiling to be wet from dripping above it.  This is relatively common, but is not always noticed.  Do the ducts run near the spots?  What type of ceiling do you have - plaster, drywall, suspended, something else?  How does the moisture show up - damp spots, water dripping, mold growing, something else? The more info you can present, the better the answer.  Of course, nothing beats in-person observation.

 

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)

 

 

 

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