By Tracy Dacko
From the April 2024 Issue
Avant garde museum designs often require concrete and steel structures to penetrate insulated walls and roofs, allowing heat energy to flow from heated interiors to cold exterior environments. In addition to wasting heat and increasing carbon emissions, thermal bridges can chill interior surfaces adjacent to structural penetrations, forming condensation and mold.
A potential problem in any modern airtight building, mold is a larger problem in museums. To preserve invaluable artifacts and paintings, museums typically maintain above-average humidity levels which, together with a steady stream of visitors off-gassing, can reach 40 to 50%.
Various factors within a building influence its humidity, and for museums, a critical concern is thermal bridging where concrete and steel structures pass through the building envelope. If left uninsulated, the chilled interior side of these structural penetrations can reach dew point and support mold growth, which threatens the museum’s collections as well as its structural integrity. Additionally, mold becomes airborne long before manifesting visibly on walls and ceilings, exposing occupants to a potential health hazard, and museum management to potential liability and costly remediation.
Preventing Mold Through Insulation
Designed for concrete-to-concrete, steel-to-steel, or concrete-to-steel connections, structural thermal break modules are installed where balconies, slab edges, steel beams, eyebrows, parapets, rooftop connections and other structures penetrate the insulated envelope. By reducing heat loss by up to 90% at the penetration, they prevent adjacent interior structures from becoming chilled, forming condensation and supporting mold growth. As load-bearing assemblies, they also transfer bending moments and shear forces equivalent to conventional monolithic structures, even in seismic locations, and can be used in a variety of applications for museums large and small.
Here are five examples of thermal break modules being used in museums.
National Museum of African American History and Culture
Completed in September 2016, the National Museum of African American History and Culture (NMAAHC) is the world’s largest museum of its kind, and the first Smithsonian museum to obtain LEED Gold certification. The museum houses exhibit galleries, a theater, administrative offices, and collections storage.
A last-minute design change called for rooftop cooling towers, requiring a new rooftop structure in which a steel truss frame is overlaid with poured concrete and topped by a membrane and insulation. The building’s cooling towers are supported by steel posts penetrating the roof’s insulation, where the building is most vulnerable to thermal bridging.
Exhibit space and priceless artifacts lay directly below the roof’s cooling towers. To prevent thermal bridging, condensation and mold growth, thermal breaks were installed to insulate and support the cooling tower support columns where they penetrate the building envelope.
Structural moments at the rooftop are transferred and the load of the cooling tower is transmitted by the thermal break modules, which are arranged in a quad pattern of four modules at each of four penetrations through the roof, for a total of 16 per cooling tower.
By addressing thermal bridging, structural thermal breaks prevent condensation and mold growth, while reducing heat energy loss at each penetration by up to 50%, contributing to sustainable design and NMAAHC’s LEED certification goals.
The Kimbell Art Museum
Located in Fort Worth, Texas, the Kimbell Art Museum is known as much for its architecture as it is for its art collection. Originally designed by Louis Kahn, the museum added a pavilion in 2013 designed by Renzo Piano to house special expositions and education programs.
The light and airy 90,000 sq. ft. space features a louvered roof system and other energy-saving devices to offset the Texas heat. Only a third of the interior is above ground, greatly reducing demands for heating and cooling. The pavilion also features a publicly accessible green roof, solar panels and structural thermal breaks.
The roof system on the eastern part of the building is supported by a total of 29 pairs of 100-foot, laminated wood beams. The beams include steel headers and are connected in pairs using steel-to-steel thermal breaks, providing a column-free space for the full width of the 102-foot bays
Concrete-to-concrete connections were also used to prevent thermal bridging where concrete parapets connect to the building’s nine inch thick concrete roof that is covered by a live lawn.
Indianapolis Museum of Art
The Ruth Lilly Visitors Pavilion at the Indianapolis Museum of Art provides a place of reflection on the relationship between building, nature, and art.
Designed by Marlon Blackwell, the deck, walls, and roof are supported by a steel exoskeleton and covered in ipe wood slats that form a semi-transparent sheath over and around the program space. The multipurpose room is surrounded by glass on three sides with a charred cedar rainscreen. The roof is supported by large steel beams which span from the interior to the exterior canopy. Structural thermal break modules were installed in the layer of insulation between the two end plates of the steel beams to reduce heat transfer and improve occupant comfort in the interior spaces.
International African American Museum
Located in Charleston, South Carolina, the International African American Museum houses a memorial garden, a genealogy center, and open spaces for exhibits and educational programs
Designed by Pei Cobb Freed & Partners in collaboration with Moody Nolan, the building is a one-story structure raised 13 feet above the ground on a double row of cylindrical columns.
Steel circular stairs providing egress from the building’s waterfront side, are attached at the second and fourth landings to the building’s interior I-beams, posing a potential thermal bridging problem. Steel-to-steel structural thermal breaks were installed at these attachment points, in line with the building envelope, preventing heat energy from flowing unabated through the otherwise insulated building envelope, and in turn, condensation and mold from forming on adjacent interior structures during cold winter months. Each thermal break provides requisite structural integrity while reducing heat energy transfer by up to 74%.
Contemporary Arts Center
Designed by renowned architect, Zaha Hadid, and built in 2003, the Lois and Richard Rosenthal Contemporary Arts Center in Cincinnati, Ohio, was hailed as “the most important American building to be completed since the cold war.” It was reportedly the first North American project for Zaha Hadid, as well as the first North American building that utilized Isokorb structural thermal breaks.
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The 91,500 sq. ft. space houses exhibit galleries, a children’s interactive “UnMuseum,” a black box theater, an auditorium, educational spaces, administrative offices, and a cafe. Structural thermal breaks were specified at concrete-to-concrete and concrete-to-steel connections in the cantilevered elements of the building design.
Modern Methods Preserve Museum Artifacts
Just as museums endeavor to illuminate, educate and preserve legacies from the past, modern construction methods and innovative technologies provide sustainable solutions to conserve energy and safeguard health in the built environment, now and in the future.
Do you have a comment? Share your thoughts in the Comments section below, or send an e-mail to the Editor at jen@groupc.com.
