Smithsonian's National Museum of African American History & Culture
The Smithsonian's National Museum of African American History & Culture in Washington, DC.
NMAAHC at twilight, April 2016. The three-tiered corona of the National Museum of African American History and Culture symbolizes faith, hope and resiliency. (PHOTO CREDIT: Smithsonian)
Structural thermal breaks were installed to prevent thermal bridging where the cooling towers penetrate the rooftop
Four Isokorb® T thermal breaks at each of four steel rooftop penetrations per cooling tower prevent thermal bridging between exterior and interior environments while supporting loads. (PHOTO CREDIT: SmithGroupJJR)
The National Museum of African American History and Culture provides a sensitive environment that balances energy efficiency and comfortable humidity levels against the need to protect priceless artifacts from the damaging effects of interior condensation.
To help achieve this delicate balance, rooftop penetrations through the building envelope were insulated from interior support structures using the latest in structural thermal break technology.
The National Museum of African American History and Culture (NMAAHC) is the first Smithsonian museum to aim for the prestigious Leadership in Energy and Environmental Design (LEED®) Gold certification. It is also the first to incorporate structural thermal breaks as part of an over-arching conservation strategy.
According to Marcus Wilkes, SmithGroupJJR Principal, the biggest risk to a museum’s “mission critical” function, from a building envelope perspective, is thermal bridging, in which structural concrete or steel penetrations such as at rooftop connections, canopies and balconies conduct cold through the insulated building envelope and dissipate it into the warm interior environment during winter months. In addition to wasting energy, these chilled penetrations can form condensation on the warm interior side of the building envelope, especially where humidity is sufficiently high enough for the exposed cold structure to reach the dew point, such as at a museum. As a result, mold can grow on cold surfaces, threatening building occupants and the museum’s collection, years before it becomes visible on interior walls and ceilings.
Exhibit space lies directly below the roof’s cooling towers, so any potential for thermal bridging had to be eliminated to protect the collection. Structural thermal breaks provided the solution to the problem. “They were the only option,” Wilkes said.
Schöck engineers assessed factored loads from the self-weight of the cooling towers and the wind at roof level to determine the number of thermal breaks required to attain continuous insulation and support throughout the roof structure.