Evaluating Options for Mitigating Environmental Risks in Historic Structures with Limited Mechanical Control During Hot and Humid Periods

The Morris County Park Commission (MCPC) in New Jersey tested six limited mechanical and passive approaches to reduce impact from high temperature and moisture loads on collections, staff, and visitors within their historic houses during hot and humid summers. Testing occurred over three and a half years in three different historic structures, and examined overall effectiveness and financial cost, while acknowledging architectural and interpretive considerations. It was found that dehumidifiers were able to reduce high moisture levels within the immediate area. Window air conditioning units were only effective when run continuously, making them less cost-effective. Conservation heating was heavily dependent on the temperature and moisture conditions of the summer, preceding its use in the fall. Testing passive means revealed that cabinet storage furniture was effective in moderating risks due to extremes or swift changes in moisture levels, while enclosures were less effective but still provided some level of buffering. Curtains were important in reducing thermal loads. This suggests that, for MCPC, passive measures may be the most cost-effective approach to the preservation of the collections.