By Melanie Islam
It’s undeniable that preserving an existing building is one of the most sustainable building actions. Embodied energy is conserved and environmental impacts are limited by building reuse. Yet, nearly 74% of the energy produced in the U.S. is used to operate buildings and 38% of CO2 emissions are byproducts of buildings. Inefficient building operations are a result of many things that can be contributed to a building envelope’s response to the natural elements, specified equipment and its performance, or user behavior.
Existing building stock represents a majority of building portfolio and addressing the role historic buildings have in positively reducing the larger impact buildings have towards the environment requires a holistic approach that involves all parties – owner, consultant, and occupants—in the decision-making process. By applying the “SWOT process” to building analysis, all parties have the opportunity to understand why historic buildings are inherently sustainability, while identifying the challenges to meet energy efficiency targets.
For example, we know that many historic buildings were originally designed to be passive and low-energy structures. These buildings have tall ceilings with operable windows, beautiful day lit stairwells, good wall-to-window ratios, and facades that respond to the local climate conditions. All of these qualities support key sustainability strategies for day lit and naturally ventilated spaces.
But, historic building envelopes are often poor thermal barriers, as the walls, roof, and windows lack the required U-value to accommodate for the temperature difference between indoor and outdoor air caused by the introduction of air conditioning. A solution to this problem could be to insulate the walls or roof and properly seal windows and doors to reduce coolth loss by infiltration. This may not be the exact answer, but the point is, solutions similar to challenges above are available. Challenges that do not have clear prescriptive answers require the SWOT analysis to provide unique solutions. The relationship between energy efficiency and human behavior is an example.
Occupants can be the greatest champions or enemies in the journey towards energy efficiency. Users will either support energy goals or resist them because it requires change. Engaging occupants in a conversation about opportunities and threats can provide a forum to discuss how key efficiency strategies that are dependent on human behavior – types of energy loads and usage, phantom and plug loads, and temperature control, can be implemented. Outcomes can provide unique building based solutions like tenant incentive plans that rewards occupants that meet established energy targets, or it can simply be a processes of establishing occupant ownership for their space.
This process is one method of interpreting what Bill J. Murtagh, Ph.D., a pioneer in historic preservation wrote, “at its best, preservation engages the past in a conversation with the present over a mutual concern for the future.” Whatever the process is for a particular building, the ultimate message is to finding a harmony that exists between rehabilitation and sustainability to ensure that our historic resources are retained yet, resilient to the modern challenges of today.
Melanie Islam, AIA, CDT, LEED AP BD+C, is President/MLAB Chair for U.S. Green Building Council Hawaii.