by Susan Pranger
The time to prevent climate change has passed. Although we must still accelerate efforts to slow resource depletion and global warming, we must also prepare for inevitable changes caused by global warming. Sea-level rise and extreme storms are already occurring, as are changes in daily weather patterns. These conditions will impact us on many scales — from our personal comfort to the global economy. Climate changes affects the environment, agriculture, our cities, and our buildings.
Our political, social, and economic structures will be stressed and reconfigured in ways we probably cannot even imagine today. And yet we must respond aggressively to this uncertain future, be sensitive to the unforeseen ripple effects of our actions, and develop strategies that are resilient and flexible.
There is much talk about the need to conserve the embodied energy of our existing buildings, buildings that will be directly threatened by severe weather, wind-driven rain, increased humidity, temperature and salts, and UV-B rays, and subjected to damage, deterioration, flooding, rot, efflorescence, and insect damage. Climate change can also indirectly threaten existing buildings by prompting man-made renovations that are intended to resist weather and conserve energy but inadvertently cause damage.
Historic buildings may very well be the canary in the coal mine. They are particularly vulnerable to both climate change and man-made interventions because they were built under very different conditions. At least in New England, most of our historic buildings were imperfect and leaky, hot and humid in the summer and cold and dry in the winter. If they still survive today, it is likely because they adapted to the weather rather than resisted it. They “breathe,” expanding and contracting with changes in moisture and temperature, and are rebuilt, repainted, and restored when needed. Efforts to control moisture migration are often unsuccessful, trapping or diverting moisture. Excess insulation can cause historic masonry to remain cold and wet, subject to efflorescence or freezing, and resulting deterioration, cracking, or spalling.
Fortunately, today most architects, engineers, and conservationists recognize that they must first understand each building’s idiosyncrasies of construction and performance and then analyze the probable, but unpredictable, impact of changes. Our knowledge and ability to model the performance of materials and systems is more sophisticated than ever, but the results can be as flawed because the materials and systems themselves are flawed. Hand-crafted masonry, for example, is less homogeneous than later machine-made masonry, and few vapor barriers are installed without a few gaps and cracks. Many preservationists are favoring modifications that are incremental and reversible, and can be monitored, altered, or removed if necessary. Storm windows, weather tightening, and efficient controls might be more effective and less stressful than the wholesale introduction of insulation. Storm windows in one condition work great, while they cause condensation in the next. Regular maintenance and monitoring are key to maximizing the performance of any building.
Another reason that historic buildings have survived is that they are revered as an important part of our culture and history. The Old State House, built in 1713, has been renovated multiple times and is undergoing additional masonry repairs this fall. As architects and engineers develop strategies for making historic buildings more resilient and struggle to maintain the embodied energy of existing buildings, owners and caretakers must weigh the benefits of physical changes that might help the building survive against the historical authenticity, cultural importance, and aesthetic features that make the building worth saving. The ability of designer and owners to find this balance will impact the shape and character of our future cities.
Susan Pranger, AIA, LEED BD+C, is a member of the Boston Landmarks Commission, and is currently teaching and studying sustainability at the Boston Architectural College.