Track 4: This New World: Preservation technology and emerging issues within our historic buildings and built landscapes
4 - Combating Condensation at The National Air and Space Museum: Reintroducing Humidification into High-Performance Landmark Enclosures
Tuesday, September 25
8:30 AM - 10:00 AM
The National Air and Space Museum (NASM) on the National Mall in Washington DC was an icon addition to the Smithsonian Institute museums when it opened in 1976. Designed by the firm of Hellmuth Obata + Kassabaum (HOK), it opened in time for our National bicentennial to celebrate America’s heritage of air and space exploration. Gyo Obata’s vision for this Late Modernist museum varied from the primarily Classical Revival and Beaux Arts of the previous buildings bordering the National Mall. The building was to be designed as a spacecraft itself, using the lightest construction, new materials, and pressing the envelope on how these materials were used in a high-performance enclosure.
Defined standard temperature and humidity ranges were first introduced into an America museum in 1908 following the newly emerged practices of European counterparts. NASM followed this practice to insure the protection of its irreplaceable collection of artifacts. However, in the more than 40 years since its initial opening, the museum enclosure has suffered from performance problems that have included water and air leakage, condensation, and thermal performance that has fallen behind current best practices for energy performance. The mechanical humidity control was abandoned early in the museum’s life because of practical issues with maintaining such humidify levels. The Smithsonian Institution is now embarking on an ambitious and comprehensive rehabilitation project that will include reintroducing mechanically controlled humidity.
The presenters will use the original building enclosure design and upcoming enclosure rehabilitation as a case study. They will discuss fundamental requirements for high-performance building enclosures, the shortcomings of condensation control for first-generation high performance buildings, and sound technical design concepts for rehabilitation that are nonetheless respectful of the historic stature and architectural significance of the building. The presenters will outline how condensation control has always been a performance requirement for architects to resolve, but modern design constraints and project complexity are forcing condensation control to the forefront of design when preserving these buildings for future generations.
The presentation will focus on the large atrium galleries that house aviation collections under expansive views of the sky through the glazed curtain walls and skylights. Included will be an examination of the inherent conflicts between maintaining the original visitor experience, the limits of the air distribution layout, and low tolerance for condensation. The presenters will discuss the modern fenestration materials, detailing principals, and analysis techniques, including thermal and computational fluid dynamic (CFD) modeling, used in the rehabilitation design. By comparing these computational methods to tried-and-true design practices, the presenters will explore scenarios where the modeling may and may not be appropriate and how it is being used to again bring the performance of the building to the forefront of what is possible in museum design.
- Explore the history of the National Air and Space Museum and identify the unique requirements of a large-scale museum revitalization.
- Discuss the fundamentals of condensation in building enclosure systems.
- Identify common and unique project circumstances that may warrant further condensation analysis to avoid issues.
- Explore the computational analysis methods available, including thermal modeling and computational fluid dynamics (CFD), and discuss the limitations of each.