By Joshua Bowditch
Expansive glass systems, as a result of contemporary advancements, have become a factor to sustainability in the building industry, and that is featured at Sarasota Memorial Hospital – Venice (SMH-V). Sustainability can be defined as eco-friendly, efficient, and resourceful, and in regards to construction can be considered on the basis of building materials, specifically raw materials, supply chain, and characteristics of the end product. The basic components of building materials are geological resources which must be processed to some extent. The SMH-V project features high-performance glass units by Tecnoglass framed by an advanced curtain wall system by West Tampa Glass Company.
The high-performance glass units are 1-5/16” nominal thickness, comprised of three plies of 1/4” glass; specifically, one ply of 1/4” clear glass with R44/21 coating at the inward surface, plus 1/2” airspace, plus two plies of 1/4” clear glass with an SGP laminate interlayer. The acronym R44/21 stands for Tecnoglass R-series low-E with nominal light transmittance of 44% and solar heat gain coefficient of 0.21. The term “low-E” refers to reduced emissivity of heat from the glass surface. The low-E technology utilized by Tecnoglass is magnetic sputtering vacuum deposition (“MSVD”)1, in which metal particles such as silver, titanium, zinc, and tin2, are deposited onto the glass surface in vacuum chambers3, to form a microscopically thin coating with spectrally selective, infrared reflecting properties. Variation is given to the glass with random panels having ceramic frit. The impact resistant laminate interlayer is SentryGlas® Plus (SGP) ionoplast, which is a significantly stronger alternative to PVB interlayers, allowing for more expansive glass panels at determined loads, resulting in potentially reduced cost and weight of the overall curtain wall system4. The glass units were fabricated by Tecnoglass in Barranquilla, Colombia. Shipments of glass units were wrapped in plastic wrap and packaged in wooden crates with foam cushioning2, and transported by bulk cargo ship. The selection process for the composition of the glass is based on specifications given by the design professionals and free market competitive pricing. Therefore, companies like Tecnoglass strive for innovative high-quality products and competitive prices.
The term “curtain wall” refers to aluminum framing that supports the glass. The emphasis of curtain wall design is to allow for expansive glass panels with the capacity to withstand high wind pressures and impact of projectiles, and to have efficient closure at the joints to prevent intrusion of moisture into the building envelope. The WTG-700 SSG curtain wall by West Tampa Glass Company is a preglazed system, meaning the glass is sealed to its aluminum frame at the factory as opposed to on-site. With preglazed systems, the glazing (sealant) is applied and cured in a controlled environment, where there is no variation of temperature and humidity, and no exposure to airborne contaminants5. The structural sealant Dow Corning 983 is used at the glass to aluminum interface, at the interior side of the glass, and Dow Corning 795 is used as a weatherproofing seal at the exterior side of joints6. With this configuration, the sealants also function as a thermal break, reducing thermal conductivity. Dow Corning 983 is a two-part sealant7; two-part sealants chemically cure within a few hours after mixing5. The size and weight of the dispensing pump required for applying two-part sealants makes field applications impractical5. The advantages of a preglazed system are threefold: quality control of assembly, exterior side hermetically sealed to prevent moisture intrusion, and expedited installation. The aluminum profiles for SMH-V were extruded by Alutions, and consist of over 50% (approximately 60%) recycled scrap aluminum8.
The use of expansive glass contributes many sustainable aspects to the project. Glass allows natural light which is not only a light source, but is also psychologically beneficial to the occupants. The glass, featuring advanced low-e coating technology, is spectrally selective, providing high solar heat control while allowing high visible light transmittance. Glass is produced efficiently from abundant and readily available silica sand. Glass is impermeable, which is an invaluable characteristic in the hot and humid climate.
Aesthetically pleasing as the SMH-V may be, these aspects described would be generally unknown. 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”.
Special thanks to Roger Campla of West Tampa Glass Company for specifics on the curtain wall system.
1The Power of Quality. 2022. Tecnoglass.
2Processed Glass. Environmental Product Declaration. Tecnoglass, Inc.
3Tecnoglass Annual Report 2021
4SentryGlas® Product Portfolio. 2019. Kuraray
5Takish, M. S., M. H. Haugsby, C. M. Schmidt, and W. J. Schoenherr. 1989. Structural Silicone Sealant Curtain Walls: Field or Factory Glazing? In: Science and Technology of Glazing Systems, ASTM STP 1054, American Society for Testing and Materials, pages 58-65. C. J. Parise (ed.)
6Product Approval #12809.2 (WTG-700 System by West Tampa Glass Company).
7Dow Corning Americas Technical Manual. 2002. Dow Corning Corporation.
8Anodized and Painted Aluminum Extrusions. Environmental Product Declaration. Alutions by Tecnoglass.