Preserving and renewing Modern architecture involves significant materials conservation and technical challenges. As the pace of industrialization advanced in the post-war period, architects embraced and experimented with new materials. Many of these materials and assemblies—curtain wall systems, stone veneer cladding, and metals—do not age well, are less durable than traditional materials, and fall short of today’s performance requirements. When coupled with the demand to improve performance for sustainability, the replacement of components often becomes a necessity.  
Preservation practitioners must consider whether the principles and practice of preservation for Modern buildings is different than traditional heritage. Addressing aesthetic and technical obsolescence sensitively in these buildings requires knowledge of Modern building techniques, as well as preservation theory and technology, to manage change appropriately. 
The renewal of Modern buildings also requires a full understanding of the designer’s original intent. When designing renovations for Mid-Century Modern architecture, the “idea” of the building must be considered in parallel with the building’s features and materials. The field is shifting to a values-based approach that focuses on a property’s significance as a central part of the decision-making process.  
This approach allows materials issues to be addressed logically and strategically. One example is reflected in QEA’s master plan recommendation for the AIA Headquarters in Washington, DC, which was designed by The Architects’ Collaborative and opened in 1973. For the upper floors, our team recommended window replacement with high-performance glazing. However, on the first floor, the monolithic double-height structural glazing (an early example) in the lobby is slated for retention. Buildings from the Modern era may also include elements that do not function as designed or intended. Creative and sensitive design may be needed to “humanize” elements that were originally less than successful. 
The sheer numbers of materials and assemblies—coatings, composites, plastics, glasses, and metal alloys, for example—found in Modern buildings means each preservation and renewal project is unique. No “cookbook” exists to guide conservation treatments and repairs for most materials and finishes. Skilled preservation practitioners are needed to address complex conservation issues. At the US Tax Court (right) in Washington, DC, designed by Victor Lundy in 1974, QEA prepared the Historic Structures Report and later worked closely with conservators to develop conservation treatments for the wood veneers in the courtrooms.  
Grounded with a quarter century of knowledge and practice in preserving modern-era buildings, the profession’s ability to address these materials and systems has advanced significantly. New technologies, tools, information exchange, and additional project experience will contribute to the wider recognition of our Modern heritage as part of the continuum of preservation practice.