Breaking the Mold with Glass and Aluminum

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Photo credit: ES
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By Joshua Bowditch

Breaking the Mold with Glass and Aluminum

Connectivity, whether with docked cruise ship or open sky and sea, is achieved with a multi-story wall of expansive glass at Royal Caribbean Terminal A at PortMiami. Architecturally, the geometry of the terminal is unconventional, seemingly fin-shaped,
and the exterior is sleek, with planar continuity through joints of differing materials. The expansive and sleek glass wall design feature is fulfilled with the CW7000 by ES. As a structural silicone glazed assembly, this system is continuously sleek at the exterior without planar interruptions, while simultaneously exceeding hurricane impact resistance and wind load requirements. Sustainability in the building industry can be considered from the perspective 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. Especially in Florida, the derivation of constituent materials in concrete is a significant environmental concern. Therefore, the use of concrete is offset with expansive glass systems, as exemplified here.

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The CW7000 is a preglazed curtain wall system. The term “curtain wall” refers to the aluminum framing that supports the glass, more specifically with the capability of spanning multi-story heights. As a “preglazed” system, the glass is sealed to its aluminum frame at the factory as opposed to on-site, so that the sealant is applied and cured in a controlled environment, where there is no variation of temperature and humidity, and no exposure to airborne contaminants1. It is also known as a “unitized” system referring to the preassembled unit. The structural sealant Dow Corning 983 is used for structurally bonding the glass to the aluminum frame at the interior side, and Dow Corning 791 is used as a weatherproofing seal at the exterior side of joints. With this configuration, the sealants also function as a thermal break, reducing thermal conductivity. Dow Corning 983 is a two-part sealant2; two-part sealants chemically cure within a few hours after mixing1. The size and weight of the dispensing pump required for applying two-part sealants makes field applications impractical1. The advantages of a preglazed system are threefold: quality control of assembly, exterior side hermetically sealed to prevent moisture intrusion, and expedited installation. The maximum size for the unitized panels is 5 feet width and 12 feet height3. Adjacent unitized panels are joined together with reciprocal framing profiles; vertically conjoined panels are known as a “stack”.

ES is part of a vertically integrated conglomerate and the products are assembled in the same manufacturing complex as processed glass operations and aluminum extrusion production. This consolidation maximizes coordination efficiency and streamlines the supply chain. These other stages of production, specific to Royal Caribbean Terminal A at PortMiami, are briefly described.

High Quality Extrusions

The material used for the aluminum extrusions is 6063-T6 aluminum. The designations refer to the composition of the alloys and the temper. 6063 aluminum has a nominal content of 0.4% silicon and 0.7% magnesium4. Billets are cylindrical masses of standardized aluminum alloy that are ready to be extruded. Billets are fed into a billet furnace for heating to a malleable state at about 900°F, then loaded into an extrusion press container, and forced by hydraulic pressure through a steel die, conforming to the cross-sectional profile of the die opening5. Upon leaving the die, quenching systems cool the extrusion at a controlled rate to establish the temper5. Pullers are used to handle the extrusion as it proceeds from the die, and the extrusion is cut to lineal size and conveyed on run-out tables for further cooling then handling by an automated stacking system. The extrusions are placed in an age/anneal oven for artificial aging by controlled thermal cycles to achieve the final temper5. The exterior aluminum finish is Duranar® Arcadia Silver, in accordance with the PPG Certified Applicator Program. Duranar® is a fluoropolymer finish meeting AAMA 2605 performance standards, which is the highest level of durability among exterior grade finishes for aluminum alloy extrusions. In the coating process, the extrusions are pretreated and the coating is applied as electrostatic liquid spray to the extrusions, then cured at specified temperature. Aesthetically, fluoropolymer finishes are glossy.

Spectrally Selective, Impact Resistant Glass

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 Solarban® 70 low-E coating at the inward surface, plus 1/2” airspace, plus two plies of 1/4” clear glass with a laminate interlayer. The term “low-E” refers to reduced emissivity of heat from the glass surface. Solarban® 70 consists of three microscopic layers of silver applied by magnetic sputter vacuum deposition (“MSVD”) and has a color-neutral exterior appearance6. The glass, featuring advanced low-e coating technology, is spectrally selective, providing high solar heat control while allowing high visible light transmittance. As Tecnoglass is a Vitro Certified International Fabricator, the Solarban® 70 coating is applied in-house7. 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 system8. If impacted, the interlayer holds the glass intact, retains the glass in the frame, and resists breaching of the building envelope8. In the glass lamination process, the glass is laminated in a closed chamber to exclude airborne contaminants and to control temperature and humidity8. The laminate interlayer is placed between two plies of glass and the excess trimmed off8. The composite is then conveyed though a preheat oven to incur partial bonding, and concentric rollers apply pressure to remove trapped air and assist in bonding8. To finalize bonding, the unit is placed in an autoclave and heated under pressure for 40 to 60 minutes8, 9.

Architectural Stewardship

Aesthetically interesting as Royal Caribbean Terminal A in Miami 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”.

Disclaimer

This article of Architectural Stewardship was sponsored by ES.

 

References

1Takish, 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.)

2Dow Corning Americas Technical Manual. 2002. Dow Corning Corporation.

3Hurricane Windows – Impact Products Catalog. 2017. ESWindows.

4Davis, J. R. 2001. Aluminum and Aluminum Alloys. Page 351-416. In: Alloying: Understanding the Basics.

5Aluminum Extrusion Manual, 4th edition. 2014. Aluminum Extruders Council.

6Solarban® 70 Product Data Sheet. 2022. Vitro Architectural Glass.

7The Power of Quality. 2022. Tecnoglass.

8SentryGlas® Ionoplast Interlayer Technical Manual. 2014. Kuraray.

9Zang, M. and S. Chen. 2012. Laminated Glass. In: Wiley Encyclopedia of Composites, Second Edition. L. Nicolais and A. Borzacchiello (eds.)

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.

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