By Joshua Bowditch
Eastlight: Window Walls in the Sky
The sustainability and psychological benefits of expansive glass in the urban setting are characteristic of Eastlight in New York City. The glass allows natural light and a sense of openness to the occupants, and is reflective from the exterior; these are strong selling points for the residential condominiums. The architectural glass systems supplier ES has been expanding into the northeastern United States market, and on this project the ES-W725 window wall system is used. ES has an array of product options and design capabilities, as exemplified here with integral components and color variations.
Product by ES
The ES-W725 is a highly efficient preglazed window wall system. The term “window wall” refers to the aluminum framing that holds the glass, spanning between floor slabs. Here however the window wall system has an integrated “spandrel module1”, also referred to as “glass slab cover2”, so that there is intermediate spandrel glass covering the edge of the floor slab. Horizontally adjacent unitized panels are joined together with reciprocal framing profiles. 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 contaminants3. The structural sealant Dow Corning 983 is used for structurally bonding the glass to the aluminum frame at the interior side1. Dow Corning 983 is a two-part sealant4; two-part sealants chemically cure within a few hours after mixing3. The size and weight of the dispensing pump required for applying two-part sealants makes field applications impractical3. At the exterior side of joints, Dow Corning 791 is used as a weatherproofing seal. The advantages of a preglazed system include quality control of assembly, exterior side hermetically sealed, and expedited installation. In some areas the window walls are integrated with the Schüco AWS 114 operable window system. Along with the ES-W725, there are a few terraces with matching ES-45T swing doors. The framing system also has a thermal break to minimize conductive heat transfer, as aluminum has high thermal conductivity. An isobar is used to thermally isolate exterior and interior aluminum components, without compromising the strength of aluminum5. 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.
The material of the extrusions for the ES-W725 is 6063-T6 aluminum alloy or 6005-T5 aluminum alloy, depending on the component1. Aluminum is lightweight, high-strength, and reflective9, and these aluminum alloys have excellent extrudability10. The exterior aluminum alloy finish is Duranar® in accordance with the PPG Certified Applicator Program, in three different colors, Hatteras White UC105261, Graphite Grey UC106708LB, and Sunstorm® Market White UC115753F, according to the architectural color scheme. Duranar® is a fluoropolymer finish meeting AAMA 2605 performance standards11, which is the highest level of durability among exterior grade finishes for aluminum alloy extrusions9. 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, and Sunstorm® has a mica appearance11.
Several different glass types are used according to the architectural color scheme. All of the glass units are insulating, with two plies of glass separated by a 1/2” insulating airspace filled with argon gas. Argon gas is invisible and nontoxic, having lower thermal conductivity than air. It is used in combination with a low-e coating for optimal thermal performance. Glass types include Optigray® glass and Optiwhite® glass with either N70/38 or R43/28 low-e coating, and further variation is given to the glass with certain panels having ceramic frit. Optigray® glass is described as ultra-neutral, warm light gray in exterior appearance6. OptiwhiteTM glass is low-iron, extra-clear glass7. The N70/38, Tecnoglass N-series (Neutral) low-e with nominal light transmittance of 70% and solar heat gain coefficient of 38, contributes a neutral to silver blue exterior appearance, and the R43/28, Tecnoglass R-Series (Reflective) low-e with nominal light transmittance of 43% and solar heat gain coefficient of 28, contributes a reflective exterior appearance with cool color tones8. Ceramic frit is an enamel that can be applied as fully opaque coverage to the glass, or in various patterns and degrees of coverage. Here in some cases a solid frit of the color “smoke” is used as a backdrop for 30% coverage pattern of white.
Aesthetically interesting as Eastlight may be, these aspects 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”.
This article of Architectural Stewardship was sponsored by ES.
1ES-W725 Technical Datasheet. 2016. Energía Solar (ESWindows).
2Architectural Guide. 2020. ESWindows.
3Takish, 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.).
4Dow Corning Americas Technical Manual. 2002. Dow Corning Corporation.
5Company Brochure. 2015. Alutions (Tecnoglass).
6Optigray® Technical Product Data. 2020. Vitro Architectural Glass.
7OptiwhiteTM. 2013. Pilkington (NSG Group)
8Low-E Series. 2019. Tecnoglass.
9Aluminum Extrusion Manual, 4th edition. 2014. Aluminum Extruders Council.
10Davis, J. R. 2001. Aluminum and Aluminum Alloys. Page 351-416. In: Alloying: Understanding the Basics.
11Architectural Liquid Coatings Color Guide. 2018. PPG Industries, Inc.
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.