IPI’s Sustainable Preservation Practices Webinar Series

Our second round of NEH-funded educational webinars has been incredibly successful – over 1,060 individuals have signed up, representing institutions from every state in the US and over 40 countries worldwide. We try to incorporate some question and answer time at the end of each presentation, but the format doesn’t allow us to get to every question. We do review and try to respond to any unanswered questions from the webinar chat log and those included in the follow-up surveys. You can always email us if there is something about managing you environment that you have a question about. IPI’s Preservation Environment Specialist Jeremy Linden answers one common question below:

Question:  In our library storage facility (in New York City) we have the possibility of achieving a 70°F and 50% RH environment.  Is there a reason NOT to maintain that even if it is possible?

Answer:  There are situations where 70/50, due to outdoor environmental conditions or mechanical system design limitations, may actually be the best collections environment for both preservation and energy. However:

  • 70/50 is not, in and of itself, the best condition from a preservation perspective – if held year-round, those conditions (using the dew point calculator) produce a Preservation Index (PI) of 39 (the PI is an indication of the rate of chemical decay). We can do better.

Use your outdoor weather conditions and whatever ability to you may have to control moisture content (dew point) during the humid months to choose operating set points that are the most appropriate for both preservation quality and energy consumption:

  • In summer, if you have an HVAC system that dehumidifies by sub-cooling and reheating, you may be able to improve preservation and reduce energy costs by decreasing the set point temperature.
    • In a general library collection, a set point of 66°F/56%RH (which uses the same 50°F dew point as the 70/50 condition) will slightly increase the preservation quality of the environment (PI of 42), without causing mechanical damage, while using less energy on reheating the air, saving energy.
  • In winter, if you are heating your space, maintaining that 70/50 condition means heating more than necessary for the books, and humidifying to a 50°F dew point.
    • By changing the set point conditions to (for example) 65°F and 35% RH with a 36°F dew point, the PI increases from 39 to 85, poses no risk for mechanical damage to collections, and uses less energy in both heating (lower space temperature) and humidifying (lower dew point to maintain).

It isn’t always possible to improve on 70/50 – but if you can define your preservation goals and needs (slower rate of chemical decay, low risk of mechanical change, for example), find out what (if any) capability you have for moisture control in your HVAC system (either humidifying or dehumidifying), and invest a little time in understanding how the system uses energy, there are often opportunities for using adjusted set points to either increase preservation quality, save on energy usage, or both.

You can learn more about this series by visiting www.ipisustainability.org.