When a prominent football franchise moved to the greater Las Vegas area, the expectations for their new home, Allegiant Stadium, were predictably through the roof.

Architects on the project were tasked with delivering a one-of-a-kind design that, in turn, created multifaceted challenges for the engineering team. One of those challenges was HVAC and air distribution in the vast venue. The complex bowl geometry of the space created a myriad of obstacles for air dispersion, ventilation, and airflow. To maximize the fan, player, and attendee experience, the ability to direct airflow was essential.

After evaluating the plans, the mechanical engineers of record on the project, Smith Seckman Reid, Inc. (SSR) and the mechanical contractor, Harris Company, partnered with fabric duct manufacturer DuctSox to find a different approach — an innovative fabric duct solution they felt would better address indoor air quality, acoustics, customization, and cost challenges.

“From the moment we designed the fixed roof stadium, I understood there would be considerable cooling requirements for the seating bowl environment,” said David Manica, President at MANICA Architecture. “Those cooling requirements would need to be supported by massive supply ducts that would be clearly seen wrapping around the building, so it was critical that we do something new and innovative to simultaneously solve the functional and aesthetic standards of the project.” 

Besides comfort in the seats, DuctSox also provided an extensive system to cool the perimeter of the stadium. Nested inside the structure, 2,550 feet of 38” – 62” diameter fabric DuctSox uniformly disperses airflow across the surface of the iconic black glass that is critical to the stadium’s aesthetic. Metal ductwork alternatives would have had harmful impacts to the glass casing due to their non-uniform thermal impact. As metal diffusers are spaced far apart, only the glass in the direct line of the opening would have been cooled, potentially causing an adverse reaction over time.

The implemented fabric duct system also features DuctSox’s Skelecore™ internal framework to eliminate risk of inflate/deflate, while also protecting the product’s integrity over the stadium’s lifecycle.

Fabric ductwork inherently lacks the resonating properties of metal. By using a fabric system, the HVAC system noise generated by metal grilles and balancing dampers was minimized. Venue sound could be dampened and redistributed evenly throughout the space, making for clear and comfortable acoustics. 

Staying Flexible

Aesthetics are another key aspect of venue experience. From its sleek domed exterior to the iconic black-and-silver color scheme throughout the interior, Allegiant Stadium reflected the cutting-edge charisma of the team’s brand. The HVAC and air distribution equipment needed to match that same visual standard. Unlike metal ducts, fabric duct systems can be produced in an array of shapes, sizes, and colors. This flexibility allowed the design team to rethink the traditional norms surrounding bowl ductwork and provided the architects at MANICA another resource to achieve their artistic vision.

Due to the limited design flexibility of conventional metal duct systems, architects and design teams have long installed the traditional ducts as high as possible in a venue to remove the equipment from view. That was not the case at Allegiant Stadium. Instead, an oval fabric duct system – the world’s largest – was suspended from the stadium roof to create an architectural ribbon element along the entire upper seating bowl. Choosing the classic black brand color, the procurement team at DuctSox aligned custom fabric threads to ensure color tones were consistent throughout. This marrying of form and function provided a striking design feature and a comfortable environment for fans as the fabric duct system was fully integrated into the space (and not hidden from sight).

Customization was essential, too. Three scoreboards interrupted the path of the fabric duct system along the exterior of the bowl. To ensure a smooth transition between the ducts and scoreboards, custom “wings” were developed in a color-matched fabric from DuctSox to help retain visual consistency.

Download our design manual to learn more about fabric ductwork solutions.

Cost Advantage

A multi-billion-dollar stadium project is always considering costs and Allegiant Stadium was no exception. In the case of its ductwork system, the fabric option offered a $6 million savings versus metal. Fabric ductwork is typically 30-50% more cost effective than a conventional sheet metal double-wall system, with much of those savings due to lower installation time.

One of the reasons for a reduction in installation time is material weight. Metal equipment is typically fabricated in singular, bulky pieces. This makes any installation process much less flexible, while the inherent weight of the metal calls for extensive equipment to hang the large ducts. Lighter fabric-based systems, on the other hand, require less structure to support them, resulting in reduced costs for rigging the venue roof structure. Additionally, fabric systems come in modular sections making installation an adaptable process for any team.

Erecting the 18-foot-long sections in place seemed straight forward enough, but considering the unusual height (up to 200 ft above field), placement directly below the catwalks, and constant changing of elevations in addition to maintaining the contour of the oval shaped bowl, it was a tall task. The team at Harris Company, the Mechanical Contractor on site, took on the challenge and developed a unique installation solution. Starting with two zip lines between field level and the scaffolding up near the installation level, segments were prefabricated on the field level then hoisted into a fixed position and indexed down the monorail to their final position. In total, this process saved thousands of hours and allowed the team to finish installation five days ahead of schedule due to the increased efficiency.

“This is Harris’ third indoor NFL stadium and first-time using fabric duct and we saw the benefits of fabric duct, not just in reductions in installation durations, but in the reduced coordination with the building structure which traditionally is half the battle with metal ductwork” said Craig Mickelson, Project Executive. “DuctSox was able to participate in our 3D modeling during design to maintain our vertical and horizontal changes in direction to follow the contour of the stadium’s shape.”