Connecting to Collections Care Online Community

Tightening Temp and RH Controls

Viewing 5 reply threads
  • Author
    • #134131
      Mat Duncan

      I’m working to bring a small museum’s collections storage space up to minimal standards of preventive conservation. I’ve installed UV radiation filters on the existing lighting fixtures and limited their use, tightened security, removed as much wood, composite, cardboard, foamcore, un-coated steel, plastics etc. as possible and substituted powder-coated racks and shelving, buffered storage boxes and folders, and other archival materials wherever possible; as well as creating schedules for regular cleaning with HEPA filtration vacuum equipment. But the temperature and relative humidity of the space fluctuate a little too widely on a day-to-day basis for my liking.

      Could anyone suggest a technology we could implement in the collections storage room to control these fluctuations? The space was, unfortunately, not designed with temp and RH control in mind and we can only address these through the existing HVAC system. The space is about the size of two two-car garages, and is below ground.

      Our current temp and RH levels are:
      temp(°): 70± 4 (seasonal swing 10°)
      RH(%): 45± 11.5 (seasonal swing 15%)

    • #134134
      Anne Schaffer

      Hi Mat,

      Specific technology to further control environmental fluctuations is outside my area of expertise, so I’ll check with an expert and get back to you.

      At first glance, though, it seems that you’re achieving pretty decent environmental controls in your space, aside from a bit of a low RH dip. It would be helpful to know the makeup of your collection and the rate of swing – certain items in your collection might benefit from stricter environmental controls, particularly stricter control of RH. A humidifier or two could be effective in a smaller space, but would require quite a bit of monitoring.

      I’ll be in touch soon, but in the meantime, you might be interested in a previous C2C discussion that discussed a variety of opinions on environmental controls:

      -Anne Schaffer

    • #134138

      Matt –

      Where is your museum located?


    • #134139
      Mat Duncan

      The collection is composed mainly of framed oil paintings, prints, & drawings, with a few stone sculptures, ceramics, and unstretched canvases and unframed drawings. About 1,400 works in all. Our museum is located in South Carolina, which is the reason why RH can be problematic. The RH fluctuations and temp fluctuations concern me in regards to the paintings, particularly the older works.

    • #134159
      Tara Kennedy

      Hi Mat-

      Seasonal drift is actually OK. What you want to avoid is rapid, constant swings in relative humidity and temperature. Those cause the most damage. For example, I’ve seen systems jump 10% RH within an hour. That’s bad. 10% RH over a series of months? That’s fine. Especially if you’re not seeing any evidence of damage in the collections. Also, objects do acclimate to environments over years of exposure, so it might be that the framed paintings are OK with the environment that they are currently living in. If you don’t see evidence of damage (e.g. tearing of canvas, extreme cracks in paint), you are doing OK.

      That said, if there are environmentally-sensitive materials that you are especially concerned about, Anne’s suggestion of microenvironments (rooms that have specific environmental conditions for specific objects) might be in order.

      If you want more detailed assistance, please feel free to email me at tara.d.kennedy_[at]


    • #134160

      We hope that your museum was not affected by the recent floods in South Carolina.

      Boxing and closed cabinets for storage are also good ways to help buffer against temperature and RH changes. Where I am (New Mexico) we can have monsoonal summer storms that result in humidity swings from 10-30% to 100% and back over a 24 hour period. Keeping collections in closed containers or cabinets is the best way to combat that kind of shift.


Viewing 5 reply threads
  • The forum ‘Connecting to Collections Care Forum Archives – 2015 through 2018’ is closed to new topics and replies.