June 26, 2015 Preparing Historic Buildings to Withstand New Weather Impacts
Guest blogger Susan Pranger is an architect and Boston resident. The following blog post summarizes the study she recently completed as her capstone project at the Boston Architectural College for a master of design studies (MDS) in sustainable design. The buildings at HBI?s prospective project at 1786 Fowler Clark Farm in Mattapan were among those Susan used to model some of her recommendations for preparing historic structures to withstand the impacts of new weather associated with temperature changes.
Now is the time to prepare for the impacts of Global Warming on historic buildings. It is no longer sufficient to focus only on reducing energy consumption and related emissions; we must also prepare for the inevitable impacts.The general consensus among scientists is that Global Warming is already happening and is irreversible, although the rate of change and the severity will depend on our actions to reduce emissions. The risk of severe storms, changes in habitat, and both local and global changes will increase with the rise with the global temperature.
Changes in sea level, temperature, and solar radiation (UVB) may be occurring gradually, but their impact on weather patterns is complex and can occur suddenly. This past winter?s record snowfall in New England and the related ice dam damage has possible roots in global warming:
?Warmer air is capable of holding more moisture- so a generally warmer atmosphere will hold more precipitation, even in the winter. As with heat waves, the frequency of such events are generally decreasing, but their intensity is increasing (as shown by the devastating blizzards in February 2010 in the mid-Atlantic region)? (Climate Institute n.d.)
The threats of climate change are not limited to extreme storms and sea level rise. Less dramatic but equally damaging, especially for older buildings, is the potential for an increase in the rate of normal weathering and deterioration. Prolonged or driving rain and changes in humidity and temperature can create conditions that encourage mold, rot, salt damage and changes in insect habitat and range. Will buildings reach a ?tipping point? where they can no longer withstand the increased intensity of these familiar threats?
The impacts of changes in weather and man-made interventions on historic building are difficult to predict because the materials, details and assembly were often hand-made and unique. Many traditional materials, such as wood, masonry and plaster, are resilient because they adapt to the weather, absorbing and releasing moisture. Adding coatings, barriers or insulation can affect their natural ability of the building to ?dry out?. Trapped moisture can accelerate freeze thaw damage and spalling from movement of salts (efflorescence). 
Preparing historic buildings to withstand and recover from new weather impacts?while preserving its inherent character and natural resiliency – will require an understanding of how traditional materials perform, and how changes in the climate might affect this performance. Proposed improvements should enhance the natural character and performance of the building. Changes should be reversible and must be monitored for any adverse or unexpected impacts. Historic buildings may also be constrained by preservation goals or restrictions. Will changes to improve the resiliency of an historic building change its appearance? Are those changes acceptable? In the long run, enhanced preventive maintenance, allowing the building to perform at its natural best, may be the best solution.
Evaluating the capital plans and daily maintenance decisions against their impact on both resiliency goals and preservation goals can identify opportunities to prevent or reduce future impacts from gradual deterioration and storm damage. These early interventions are likely to cost less and be more effective in protecting the original materials, design and character than are emergency actions or repairs.
References
-Climate Institute. n.d. Extreme Weather.http://www.climate.org/topics/extreme-weather/index.html.
-IPCC. 2014. “Climate Change 2014; Impacts, Adaptation, and Vulnerability.”
-Peterson, Chris J. 2010. “Termites and climate change: Here, there and everywhere?” Earth. February 16. http://www.earthmagazine.org/article/termites-and-climate-change-here-there-and-everywhere.
-Safeguard. n.d. Dry Rot and Its Control.
http://www.safeguardeurope.com/applications/dry_rot.
Susan Pranger, AIA, LEED AP is a member of the Boston Landmarks Commission, and an Adjunct Professor at the Boston Architectural College where she teaches Traditional Building and Greening Existing Buildings.