The sustainability and the historic preservation movements share a common goal—being mindful stewards of valuable but finite resources. One movement seeks to wisely use energy, water, and materials, while the other seeks to revitalize historic buildings for current use in ways that maintain their rich heritage. Reconciling sustainability and historic preservation in practice poses certain challenges. With increased awareness and dialogue, however, the preservation and the green design movements can tap synergies and develop new ways of working together to the benefit of both.

Sustainable design often is associated in the public mind with the new, whether in the form of double-glazed spectrally selective glass or new technologies such as photovoltaic systems. However, sustainable design encompasses a range of strategies aimed at lessening our impact on the planet. The reuse and improved energy performance of historic buildings is a critical part of this.

Historic buildings undergoing rehabilitation already incorporate important considerations that enhance the building’s life, such as adhering to current building codes, seismic safety standards, and ADA requirements, and meeting the needs of modern-day users. Sustainable design is just another element to apply. All of these factors can be incorporated into historic buildings with sensitivity, and the Secretary of the Interior’s Standards for Rehabilitation are flexible enough to accommodate an array of solutions.

Every historic building is unique, and the approach to enhancing sustainability in historic preservation and renovation projects should acknowledge that individuality. Many buildings built before the advent of electric lighting and heating, as well as modern ventilation and cooling systems, have inherently sustainable strategies sensitive to local conditions; these strategies include porches, deep-set windows for shading, and narrow floor plates that maximize daylight and natural ventilation.

The best approach is to determine which architectural features contribute to a building’s historic value and which were originally intended to keep the structure warm, cool, or ventilated. Then strategies can be devised that minimize the impact on historic elements while working with the building’s inherent green qualities. The rehabilitation of Pasadena City Hall in California embraced the original architecture, using existing arcades as outdoor shaded corridors in lieu of constructing interior corridors, while inserting highly efficient heating and cooling systems. The new systems achieve a 23 percent reduction in energy use, contributing to a LEED Gold rating.

The planned rehabilitation of the historic Linde + Robinson Laboratory for Global Environmental Science at the California Institute of Technology in Pasadena, the first LEED Platinum–targeted renovation of a historic lab building, is designed to achieve the lowest energy use of any physical science research lab. The lab’s energy use will be reduced by more than 80 percent compared with a typical lab in this climate through a combination of strategies including a 50 percent reduction in lab equipment plug loads; radiant cooling that relies on compressor-free cooling half of the year; decoupling of ventilation air from cooling; radiant ceiling panels; low-pressure drop systems; and photovoltaic panels for on-site energy production.

One unique aspect of the project is the repurposing of a historic coelostat, a device that uses movable mirrors to reflect sunlight along a particular path, to provide daylighting to below-grade levels of the building. The coelostat consists of a flat mirror rotated by a motor to continuously reflect the sun’s light into a fixed telescope throughout the day. Since the coelostat is no longer used for scientific purposes, its 40-inch-diameter mirror will provide a direct beam of light into the building that then can be dispersed throughout the interior. As a light source, the coelostat can illuminate up to 6,000 square feet of office space at current code levels.

An additional concern that often arises is the degree to which the sustainable design community recognizes historic preservation as a sustainable value in and of itself. There is growing awareness of the need to reuse existing buildings, which will save significant resources, not only in terms of structure and materials, but also in terms of embodied energy—the energy that is required to extract, process, transport, and assemble construction materials. This is acknowledged in the LEED system by crediting the reuse of building exterior walls, structure, and interior elements.

However, LEED does not yet distinguish between the removal of materials that are historic and those that are nonhistoric, and it gives no credit for retaining windows or exterior doors for their historic value or durability. The San Francisco–based Fort Baker Retreat Group recently restored 18 historic buildings that were part of a military garrison built in the early 1900s, incorporating them into Cavallo Point, a resort hotel and conference center in the Marin Headlands of California. The design kept the buildings’ original windows rather than replace them with double-glazed windows. Given that the windows are small and the Bay Area’s climate is mild, replacing them would not have resulted in significant energy savings. Keeping them maintained the historic character and retained windows that had been in use for more than 100 years and are still durable, rather than replacing them with a product that has a shorter lifespan. Greater flexibility in the LEED system would recognize the sustainable advantage of retaining the windows and other features, which typically is not credited because of the perception that these elements are not energy efficient.

Historic structures also have the advantage of embodying cultural history. A historic building’s social value is harder to quantify than potential energy savings, but the value is real. Re-energizing historic areas saves resources and promotes socially, culturally, and economically rich communities.

Further dialog between the sustainability and preservation communities is essential. In 2006, the National Trust for Historic Preservation formed the Sustainable Preservation Coalition to advocate for better integration of preservation values into the LEED system. The organization partners with groups such as the American Institute of Architects, the Association for Preservation Technology International, and the National Conference of State Historic Preservation Officers. The coalition has met with the U.S. Green Building Council to discuss ways of incorporating into LEED such factors as the cultural value of historic buildings, and the durability and embodied energy of historic materials.

The need to merge green design with historic preservation will not go away. The goal is to find a happy medium that respects the integrity of historic buildings without being overly timid about introducing changes. In the end, sustainability and historic preservation aim for the same goal: to conserve the array of resources we presently enjoy so that future generations may enjoy them, too.

Deborah J. Cooperis a senior associate and sustainability coordinator at Architectural Resources Group.