Environmental conditions in historic house museums

May 15, 2010

On May 14, Conservator John Childs and Team Leader of Property Care Benjamin Haavik presented their ongoing work on the use of mechanical systems in historic house museums to mitigate extremes of relative humidity (RH) to about seventy-five people at the American Institute for Conservation of Historic and Artistic Works (AIC) annual conference. The presentation reviewed the failures of complex systems installed in the 1990s to achieve a strict 45% RH and discussed their current work funded by IMLS to simplify four of those systems. 

Historic New England’s current approach to environmental systems is to:

1) Collect data about the temperature and RH in the museums before, during, and after any work is implemented;

2) Understand that the majority of the objects within the structure can survive within parameters of 30-60% RH;

3) Perform corrective repairs to elements that are allowing water to infiltrate into the building and use the environmental data to measure the results; and

4) Install mechanical systems using simple controls and equipment in a phased manner and evaluate the environmental data after each phase.

Recent projects at the Hamilton House in South Berwick, Maine, and Cogswell’s Grant in Essex, Massachusetts, were highlighted. At both sites extensive ventilation systems controlled by a central digital communication panel were replaced with a simple loop of radiant heat in the basement paired with, in the case of Hamilton House, a dehumidifier. Preliminary data for both sites show a stabilization of the RH resulting in better conditions for the objects.

The appropriateness of the environmental standards in museums was a hot topic at the conference. In addition to John and Ben’s presentation on historic house museums, the fine arts museum community is struggling with the same topic. Steven Weintraub presented a paper on “The Evolution of Environmental Standards: the Struggle to Quantify and Simplify Risk in a Complex World.” There was also a roundtable discussion on the subject entitled ‘The Plus/Minus Dilemma: The Way Forward in Environmental Guidelines.”