Open Forum

Does anyone have any relevant experience they'd like to share? We have over 2,000 square feet of space housing collections, rare books, and archival materials that we'd like to better control the humidity of. The temperature is very consistent, but humidity varies more than we would like. We rent this space, so options are somewhat limited in that respect.

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Mike Cosden
Curator
Edison and Ford Winter Estates
Ft Myers FL
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I have been using portable dehumidifiers in collections spaces for over 10 years between at my former institution and my current one,  You can get a dehumidifier on wheels for about $150 with a bucket that holds abut 5 gallons.The downside is that you have to dump it once or twice a day depending on your conditions, but they do turn off by themselves when full.  If one doesn't do  the job then get two.  We are now looking at getting  a desiccant system that will dry out the air before it gets circulated.  This will relieve me of dumping the water.    However, that is a higher cost solution.  I would try the portable ones first.

Feel free to contact me off list for brand recommendations.

Marybeth

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Marybeth Tomka
Curator
University of Texas, Austin Texas Archeological Research Lab
San Antonio TX

We currently have no air conditioning in our old museum building nor in our storage building. We have purchased good portable dehumidifiers that will operate down to 40 degrees (around $250 each.)  The one in the gallery has pvc pipe running to a sink so it never needs to be emptied. The one in the storage building is piped through an exterior wall. (This one is disconnected and the hole is sealed up before winter.)  They are both very helpful at keeping the humidity in check.

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Roxanne Bassett
Executive Director
Newaygo County Museum and Heritage Center
Newaygo MI

Original Message:
Sent: 09-14-2016 07:18 AM
From: Marybeth Tomka
Subject: Utilizing Dehumidifiers in Collections Storage Areas

I have been using portable dehumidifiers in collections spaces for over 10 years between at my former institution and my current one,  You can get a dehumidifier on wheels for about $150 with a bucket that holds abut 5 gallons.The downside is that you have to dump it once or twice a day depending on your conditions, but they do turn off by themselves when full.  If one doesn't do  the job then get two.  We are now looking at getting  a desiccant system that will dry out the air before it gets circulated.  This will relieve me of dumping the water.    However, that is a higher cost solution.  I would try the portable ones first.

Feel free to contact me off list for brand recommendations.

Marybeth

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Marybeth Tomka
Curator
University of Texas, Austin Texas Archeological Research Lab
San Antonio TX

Good morning -

The Florida environment is especially challenging because of the year-round high relative humidity and elevated ambient dew points, not just the temperature. There are high-efficiency dehumidifiers available and we have often recommended them to augment cooling; however, their efficacy depends upon the tightness of the building (or space) envelope. Assuming that you cannot do anything to the building itself because it is leased space, do you have sufficient space to construct a vapor tight "box within a box" which can serve as your dehumidified space? Depending upon the type of dehumidifier selected you will also need a way to automatically drain the condensate from a refrigerant-type dehumidifier or eject the hot & humid air from a desiccant wheel.

As a conservator, I always collaborate with an engineer when addressing these types of building/collections issues because it is not as simple as installing a dehumidifier, especially in a hot and humid location prone to extreme weather events such as hurricanes. I would certainly consult with a professional engineer who has demonstrated experience working with museums in hot and humid climates; s/he should be able to provide guidance on design of the enclosure or envelope as well as systems design.

As others have recommended previously in this forum, there are a number of good resources that have recently become available. These include materials developed by the Image Permanence Institute (www.imagepermanenceinstitute.org) and the Getty Conservation Institute (www,getty.edu/conservation/).

I hope this helps.

Wendy Jessup

Conservator

Wendy Jessup and Associates, Inc.
Arlington, VA

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Wendy Jessup
Conservator
Arlington VA

In our old museum our HVAC system was having a lot of issues so we used dehumidifiers (2 in total) throughout the exhibit area, which consisted of one large room. We didn't have an up to date HVAC system till we moved to our new location which now has an HVAC system on each floor. The advice I have is that for 2,000 square feet of collections space I would use 2-4 dehumidifiers as a temporary fix. Saving up for a HVAC system, though expensive, would help in the long run. I hope this helps.

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Anne Moseley
Assistant Director & Curator
Lincoln Heritage Museum
Lincoln IL

Interesting information on this so far.

We are currently in the design/development phase of construction. However, we do have a storage facility (an old Fastenal store in an industrial park, c.4140 sq.ft./80k cu.ft.). It has AC/Heat but no humidity controls. Being in Northwest Arkansas, the humidity stays low (<45%) in the winter but is all over the place starting in May. The datalogger reports looked like a seismograph of a series of nuclear tests (40% jumps/drops depending on the day).

To fix this, we did a few things. First, determine the dehumidifier load. There are a number of sites online that can help - or call your local HVAC shop to see if they can help you make this determination. 

Second, we purchased a commercial-grade dehumidifier. It wasn't cheap @ $950. It has a long power cord and a hose that allows the water to drain. So long as you have somewhere for it to go, you are good - no bucket to empty. 

Third, we closed the non-mechanical vents in the space. We are not talking a hermetic seal in any sense of the word - there will be leakage in the space. However, we limited the volume of the conditioned air that could both escape when the HVAC was running and enter when the HVAC was not running. 

The RH% is now moderated at c.55% +/-2%. I would like to get it lower, but I can live with this. 

YMMV, Good luck! 

Dave K.

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David Kennedy
Curator of Collections and Exhibits
US Marshals Museum
Fort Smith, AR