Vertical Velocity

A stroll through the isle of Manhattan, the ultimate skyscraper city, is akin to a hike through the Narrows of Zion or the forests of Redwood National Park. The sheer rise of structures and vertical canvas of materials is nothing short of impressive, constantly shifting tones as conducted by the sky. It truly is a playground for many talented architects and builders. An upward glance at high-rise construction sites in New York City would likely reveal Enclos Corp. workers putting finishing touches on a building facade1. As is the case across the United States, Enclos is a mainstay in many cities’ curtainwall contracting market, a foothold it has gained from consistently delivering on-time.

The depth of knowledge to execute precision installation high in the sky is ingrained in our corporate identity, dating back through our lineage, which began in 1946 under the name Cupples. From the 1950s forward, when modern unitized curtainwall implementation was beginning to take-off, the firm quickly became the industry leader in curtainwall for skyscrapers, holding the claim to five of the six world’s tallest building enclosures for many years. More information on this rich lineage here.

As a participant in the construction of custom, high-performance facades, Enclos finds itself on a handful of recent and upcoming supertalls, including 432 Park Avenue, which was the 100th supertall constructed in the world when it became the tallest residential tower in the western hemisphere upon completion in late 2015. Other supertalls completed in recent years with Enclos’ involvement include 30 Hudson Yards at 1268´ (386.6 m, 73 floors, 2019), 53W53 at 1050´ (320 m, 77 floors, 2018) and Comcast Technology Center at 1121 ft (341.7 m, 59 floors, 2018). 53W53, as well as 220 Central Park South – though just shy of supertall status at 950´ (289.6 m, 66 floors, 2018) – will join 432 Park Ave in the high-end residential boom soaring over Central Park. In these residential structures, great value is placed on views, heightening the importance of the performance and aesthetics of the building facade. Additionally, higher winds, congested sites, delivery of units into the city, all are reasons that point to the prefabricated unitized curtainwall.

Keeping up with Schedule Demands

In recent years the number of supertall buildings has increased exponentially, and nowhere in the United States is this more evident than in New York City. The growth has truly been a mix of commercial and residential projects, driven in large part by developers’ desire to provide unparalleled views for luxury condo developments. That trend meshes with Enclos’ expertise in prefabrication, which is at the core of our business model. With dense urban sites, limited footprints, and aggressive construction schedules, prefabricated unitized curtain wall enclosure systems make a lot of sense.

Enclos “did whatever it took. They erected panels 24 hours a day, with excellent and performance-tested quality results”

James McKenna, President at Hunter Roberts in ENR New York1

Curtainwall units are glazed and assembled off-site in a controlled environment, then scheduled for just-in-time delivery whenever possible. The prefabricated curtainwall units use interlocking details that reduce field activities such as applying joint sealants. This approach allows for manufacturing to build-up a backlog of prefabricated units off-site so that – when the site and primary structure are ready – facade installation crews may hit the ground running, sequentially wrapping the building a floor at a time from the bottom up.

Vertical Mobility

To meet project schedules, identifying how units will elevate to their final location on the building is an essential challenge to resolve early. On project sites, a hoist is used to transport crew members and materials vertically throughout the building. It is common for facade contractors to use the hoist to lift bunks – crates or racks of several units – to their respective floors for uncrating and preparation for installation. This approach commonly uses installation equipment that is fairly mobile and is relocated up the building as it rises. Additionally, this approach of floor loading and setting does not require the use of a project’s tower crane, a high-demand piece of equipment that is as impressive as the structure it erects during construction. The tower crane, or cranes for many mega projects, is a highly-sought-after resource for many trades.

Early consideration for facade contractors is coordinating:

  • Is there access to the hoist for transporting curtainwall bunks?
  • Is the hoist dimensionally large enough to accommodate these bunks?
  • Is the hoist’s weight capacity adequate to handle the bunking plan?
  • Is a dedicated (for facade contractor only) over-sized hoist required?

The last option, a hoist provided by and dedicated solely for the facade contractor, was the approach adopted for the 220 Central Park South enclosure where large unit dimensions and weights required something more than what existed in the contractor’s site logistics plan. The limestone used in the stone-on-truss assembly of this project’s facade resulted in heavy units. Having a dedicated hoist helped avoid a dependency on the overall project’s tower crane, which could have led to schedule delays, significant coordination with other trades, or the potential for setting during off-hours such as night or weekend shifts when the tower crane is more readily available. On projects where a dedicated hoist was not possible, or over-sized units do not fit in the hoist, coordinating tower crane time during off-hours during a night shift is a common approach to vertically transporting curtainwall units.

How has design collaboration evolved on cutting-edge skyscrapers?

Not all seminal advancements in skyscrapers in recent years are related to supertalls. Take the court-scraper by Bjark Ingles Group for VIA 57 West, a 39-story, residential project completed in 2016 with the Hunter Roberts Construction Group as the general contractor. The building’s double-curved form was a prime opportunity for Enclos to showcase its problem-solving prowess, from design through construction. The prospect of making this distinctive sloped profile a reality presented a complex installation challenge that was resolved during a design-assist collaboration with the design team. Together, we derived a subdivision—completely comprised of one-off unit geometries—that met design intent, accommodated maintenance equipment, and integrated guttering based on flow-accumulations across the surface. The project was the impetus for proactive integration of laser tracking into manufacturing processes.

And for those day-to-day construction problems that technology couldn’t predict, James McKenna, president at Hunter Roberts, says Enclos “did whatever it took” to solve them. “They erected panels 24 hours a day, with excellent and performance-tested quality results,” he says1.

Installing the Views over Central Park

When installing facades on supertall buildings, one of the initial main issues is the interface with the primary structure. In projects that reach such great heights with a minimal footprint, the result is a very slender structure. To achieve these forms, it is not uncommon to see the primary structure made of concrete, as is the case in 432 Park Ave, 53W53, and 220 Central Park South. Whether it be steel, concrete, or composite primary structure, the relationship to the facade is very similar to other buildings. Where it does vary is when the structure implements a unique structural geometry like the diagrid system utilized in 53W53. The combination of sloping conditions and a concrete diagrid structure presented hard-to-reach sloped corner conditions for installing curtainwall units. As a result, a series of custom column jib apparatuses were developed to be able to lift material outside the building before swinging it into the otherwise hard-to-reach final position, ensuring safe and efficient field operations. The intersections of the sloping faces on projects like 53W53 and 30 Hudson Yards amplify the number of unique unit geometries, require heightened coordination through engineering and manufacturing, and can result in oversized atypical units that may require unique installation measures.

The construction of supertall structures is not a new challenge (see list below of supertalls completed by the Enclos lineage throughout the years), but it is increasingly more prevalent in recent years. Enclosing buildings at such great heights is a challenging task, one that requires prudent planning, a wealth of experience, and the ingenuity to problem solve (one of the best examples of this may be viewed in Peak Performance). Here we have highlighted some of the considerations the facade contractor goes through that are likely more critical on supertall projects due to the limited site and floor footprint, as well as access to and throughout the site.

To achieve speed and efficiency while upholding quality and safety in the field is the result of early collaboration among the construction team.

1 from Jim Parsons article in November 2017 ENR NY

List of supertall projects completed, topped out, or under construction in the United States with Enclos involvement*

3. Willis Tower (442 m, 1450´, 108 floors, 1973), Chicago

6. 432 Park Ave (426 m, 1397´, 85 floors, 2015), New York

8. 30 Hudson Yards (386.6, 1268´, 73 floors, 2019), New York

12. Aon Center (346 m, 1136´, 83 floors, 1973), Chicago

13. John Hancock Center (344 m, 1128´, 100 floors, 1969), Chicago

14. Comcast Technology Center (341.7 m, 1121´, 59 floors, 2018), Philadelphia

19. 53W53 (320 m, 1050´, 77 floors, 2019), New York

29. JPMorgan Chase Tower (305 m, 1002´, 75 floors, 1982), Houston

* Domestic CTBUH rankings as of August 2020

List of completed supertall projects worldwide with Enclos involvement**

16 and 17. Petronas Towers (452 m, 1483´, 88 floors, 1998), Kuala Lumpur, Malaysia,  completed as Harmon Contract

21. Willis Tower (442 m, 1450´, 108 floors, 1973), Chicago, completed as Cupples

25. 432 Park Ave (426 m, 1397´, 85 floors, 2015), New York

36. 30 Hudson Yards (386.6, 1268´, 73 floors, 2019), New York

65. Aon Center (346 m, 1136´, 83 floors, 1973), Chicago

68. John Hancock Center (344 m, 1128´, 100 floors, 1969), Chicago, completed as Cupples

73. Comcast Technology Center (341.7 m, 1121´, 59 floors, 2018), Philadelphia

111. 53W53 (320 m, 1050´, 77 floors, 2019), New York

146. JPMorgan Chase Tower (305 m, 1002´, 75, 1982), Houston

** Worldwide CTBUH rankings as of August 2020

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