Photo courtesy of Perkins&Will. Photo credit: Robin Hill

By Joshua Bowditch

Exemplary Sustainability with GateLite in South Florida

As a place for STEM learning, making application of innovation and sustainability were design priorities for the Ransom Everglades STEM Center in south Florida. Sustainability in the building industry involves careful selection of architectural materials and methods, and the GateLite panel system by GATE Precast Company was chosen to achieve these objectives. With GateLite panels, concrete and steel are used synergistically, allowing for architectural precast cladding at an unusually thin 2-1/4” nominal thickness. The GateLite panels use 60% less concrete than regular precast concrete and 50% less steel than conventional light gauge steel framing1. This is an example of the concept of dematerialization, the use of less material to fulfill an intended purpose, which corresponds to less embodied resources, and lighter weight load. The panels have the advantages of precast concrete but in significantly lower quantity of materials. From a construction standpoint, the advantages of the GateLite unitized system are simplification of the exterior wall assembly, consolidation of the construction process, and improved quality, safety, and predictability.

Photo courtesy of Perkins&Will. Photo credit: Robin Hill

Innovative Sustainability

As precast concrete typically contains steel as rebar, concrete must provide sufficient cover over the steel reinforcement2. Instead of relying on rebar, GateLite panels are innovatively supported at the interior side by a steel tube mainframe, thereby allowing the thickness of the overall concrete to be reduced. Pins of 1/4” diameter steel anchored or embedded in the precast transfer the loads to the mainframe of mild steel tube. Despite the thinness, impermeability to the exterior is provided by well-consolidated precast concrete with low water/cement (w/c) ratio3. The steel tube mainframe is prefabricated with hardware connections for efficient installation to the building structure and functions as a drywall-ready substrate, eliminating the need for furring along the walls. GateLite panels have a 2” layer of HFO (hydrofluoroolefin) polyurethane spray foam insulation, with zero ozone depletion, an ultra-low GWP (A1-A3, is 3.47 Kg CO2e)4 and R-value of 7.5 per inch1, applied at the precast facility. The foam is produced by combining two separate formulations that react and expand when combined through the application process; after the foam has cured it is chemically inert4. As a closed-cell foam, the HFO provides an air and vapor barrier at the interior side, in addition to highly efficient insulating value4.

Design Features

Resulting from design-assist collaboration between GATE and architecture firm Perkins&Will, the GateLite panels have some interesting design features. Three-dimensional reveals as subtle vertically aligned indentations in the GateLite panels result in a rippled surface texture. The reveals are tapered to a max depth of 1” and max width of 7”. To accommodate the indentations, the 2-1/4” facing was thickened to 3-1/4” with high-density foam precisely cut by CNC machining5. Efficiency of the panel system is furthered by repetition in the design. Joints between respective GateLite panels are 3/4” nominal gaps sealed by inserting backer-rod of closed-cell material and using low-modulus silicone sealant. Silicone sealants are chemically stable and extremely durable with excellent resistance to weathering and aging6. Precast concrete is inherently colored with integral pigments, and has an ingrained finish, thereby eliminating the need for repainting or refinishing. Structurally, the GateLite panels are commensurate with the post-tension system of the building structure, which lessened the quantity of structural concrete by reducing slab thickness and eliminating bulky perimeter beams. The post-tension system necessitated a lightweight exterior wall assembly, with the GateLite panels being much lighter than engineering requirements. This demonstrates the contribution of GateLite to the sustainability aspects of the overall building. The lighter loads also correspond to a lower capacity crane for hoisting in the construction process.

Detail of the panels (left) and handling at the precast plant (right). Photo credit: GATE Precast Company

Materials & Production

The GateLite panels were produced at the GATE Kissimmee, FL precast plant, which is centrally located to peninsular Florida. The primary constituents of the architectural precast concrete are aggregates, specifically crushed limestone and natural sand, which are truly indigenous. High-quality limestone is sourced from designated areas in south Florida where it is efficiently mined and processed by automated quarry equipment. Natural sand, sourced from nearby deposits in central Florida, is extracted and sorted to size hydraulically. Aesthetically, as aggregates significantly affect the inherent coloration of the architectural precast, aggregates from these respective sources have favorable color values for whiteness and consistency. The aggregates are carefully proportioned for optimal gradation of particle sizes. The steel tube of the mainframes, 5”x5” hollow structural sections (HSS), was fabricated at GATE Kissimmee and supplied by Infra-Metals in Tampa.

Architectural Stewardship

Aesthetically interesting as the Ransom Everglades STEM Center campus may be, there is more than meets the eye. It is publications like this one that can provide representation of these sustainability aspects through description and illustration. That would be the intent of “Architectural Stewardship”.

Disclaimer

This article of Architectural Stewardship was sponsored by GATE Precast Company.

 

References
1GateLite by Gate Precast. 2021. Health Product Declaration Collaborative.
2Architectural Precast Concrete Manual, Third Edition. 2007. Precast/Prestressed Concrete Institute. Page 456.
3Architectural Precast Concrete Manual, Third Edition. 2007. Precast/Prestressed Concrete Institute. Page 307
4ASTM International. 2022. Environmental Product Declaration: Spray Polyurethane Foam Insulation (HFO). Spray Polyurethane Foam Alliance.
5PCI Journal 68(2). March/April 2023. Precast/Prestressed Concrete Institute.
6Beall, C. 1999. Thermal and Moisture Protection Manual. McGraw-Hill. Page 74-81.

About the Author: Josh Bowditch

As a native resident with architectural experience and environmental regard, Josh Bowditch is intent on publishing about sustainability in the architectural and building construction industry locally. From being in the architectural profession, Josh has an understanding of the processes involved. Is it possible to reconcile environmental considerations with development? The word sustainability has various connotations but indeed can be viewed in the context of stewardship. Read Previous Article.