May 16, 2018
By Silvio Baldassarra, OAA, FRAIC
Green, patinated copper is the result of a natural aging process and has been coveted by architects and designers since ancient times. Copper does not react with water, but it does with atmospheric oxygen, forming a layer of brown-black copper oxide protecting the underlying metal. The cherished green layer of verdigris (copper carbonate [CO2CO3]) varies depending on the amount of sulfur in the local atmosphere. This natural process takes years but stabilizes to form a distinctive green patina, forever sealing and protecting the raw copper.
As executive architect for 180 Wellington St., Ottawa, the author wanted to save the copper material removed from the roof of a 1920s office building and reuse it to line the walls of a library in the building. However, the challenge was to develop a design for reusing the sheet material in an innovative manner, while resolving the library’s sound attenuation challenge. There was also a technical issue related to oil canning (deformation of thin metal sheets).
The Wellington Building underwent rehabilitation from 2010 to 2016. Situated across from Parliament Hill, the Beaux-Arts style structure now contains office suites for Members of Parliament (MPs) and committee rooms, as well as a satellite location of the Library of Parliament. The library, located in a double-height, skylit space, is reserved for the use of MPs and their staff.
An early design idea was to simply use the sheet copper material on the walls of the library. While this is not a novel approach given the application, it would have been a dramatic installation. However, the idea was rejected by the client, citing the opinion copper is “not a noble material to be used for interior finishes.” NORR Architects and Engineers believed reuse of the existing green, patinated copper to line the library was the right solution, and worked to create a design execution that would satisfy the client’s standard of a “noble” finish.
The second and final solution was technical, esthetic, and sustainable. The plan was to create a floating, sculptural copper shell in front of a perforated, precisely bent, modulated copper lining to the wall. The shells are reflective of the triangulated shapes of the roofscape of Parliament Hill. A total of 3500 floating, sculptural copper shells were envisioned, driven by the 406-mm (16-in.) width of the recycled copper material.
NORR worked with F.M. Enterprises, a copper roofing specialist, to create a full-scale prototype of the copper panel concept. The final design and completed panels were created by NORR in co-operation with Mometal Structures; EllisDon Constructors acted as construction managers.
The copper shell grid and perforated panels provide a sculptural finish to the four walls of the library. The skylight above the entire room brings the floating shells to life throughout the day as natural light moves from east to west, changing the shadows through the seasons. At night, artificial light supplements and eventually takes over with even distribution. The combination of natural and artificial light on the copper shells offers the room a dynamic, sculptural wall treatment.
It became apparent to the project team they needed to spend as much time on the design of the recovery, sortation, and preparation of the reused material as on the design of the actual solution. The first goal was to maximize the amount of copper removed by saw cutting as close as possible to the standing seam of each panel. The sheets were then stacked in crates, stored, and numbered. The material’s use was based on a survey of maximum size of panels recovered and, of course, lengths. At this point, the design team was unaware 30 per cent of the panels were 1.2-m (4-ft) lengths instead of the preferred 2.4 m (8 ft). The other concern was the quality of the green patina and whether it was consistent across all the panels. Therefore, all the pieces were assessed and sorted (usable or not) to calculate the total number of panels available for the intended design.
Initially, the team felt it had 80 per cent more than what would be needed. However, in the recovery process, and because of labour issues, storage mistakes, sortation of less-desirable pieces, as well as surprises related to useable lengths and sizes, the design team ended up with only five per cent excess. The author recommends designers plan to recover 100 per cent more material than what is required for the final design in future recovery programs.
The final part of the recovery was to take the oil-canned site material—stored in long, flat crates—for rolling and flattening prior to fabrication into the new design. At this point, the energy inputs included labour and power for sawing the panels, moving material to the fabrication shop, and flattening the sheets in a roller machine. These inputs are minimal when compared to buying new material.
The base perforated copper wall panels start 2.4 m (7.10 ft) above the library floor. The room measures 21 x 12 m (68.10 x 39.4 ft) for a total area of 705 m2 (7588.5 sf).
The starting point for the design was the available amount of recycled copper sheets. After removal and inventory measurement of all panels, it was established the maximum design module could be no more than 2.4 m x 406 mm (8 ft x 16 in.) per copper sheet. This established the modulation. All of the wall copper panels were initially roller flattened and perforated to enhance acoustic properties. To prevent oil canning in a 406-mm wide sheet and to assist in sound attenuation, the design team also decided to break press the panel in the middle and return it at each edge to fix it to a back panel. The continuous break at ± 203 mm (8 in.) at each end stiffens the copper panel, making it extremely rigid over the long 2.4-m lengths. The sheet became a “C” panel approximately 406 mm wide x 2.4 m long.
Following the break pressing of the perforated sheet copper, the back side was lined with acoustic insulation fabric. This is essential for sound absorption; sound gets captured as soon as it reaches the perforated holes. The insulation also seals the hole from dust or air moving in the cavity. The floating shells also act as sound baffles, reflecting and trapping noise in the back, perforated wall panel.
The individual 406-mm x 2.4-m long copper sheets were shop-assembled vertically on aluminum panels approximately 3 m (9.8 ft) wide and ± 1.7 m (5.5 ft) high. The aluminum structures were constructed of 50 x 50-mm (2 x 2-in.) aluminum with an additional 3-mm (1/8-in) aluminum back panel. These perforated panels are designed to be picked up and erected to very tight tolerances onto a structural steel framing system. A gap of ± 152.4 mm
(6 in.) between the vertical panels allows some tolerance, but in essence, near perfection is required to set the panels in place.
The triangulated, sculptural copper shells are the centrepiece of the design. The shells were created by simply folding a 406 x 406-mm sheet of recycled copper riveted onto itself.
Creating one shell is simple, but creating 3500 of them in perfect shape and alignment—vertical and horizontal—with each other was a difficult task. Each shell had to be cut perfectly and folded on a break press consistently every time. After repeated attempts, the fabricators developed a precise jig to set a series of shells vertically on a rod, which would in turn be hung on the back panel. The jig allowed for vertical and horizontal adjustments of each shell to ensure they were aligned in every direction.
Another key to the fixing of the shell to the vertical rod is the yoke, which holds it securely. Once set, the shell is not allowed to move in any direction.
As mentioned, a structural framework supports the individual panels, which were shipped completely assembled with perforated copper and shells. Onsite, the panels were bolted into place and the final gaps between panels and corners were completed. The time and effort spent in the design and shop preparation was a major advantage during installation. The panels went together without any flaws.
The final design is functional and esthetic, but what cannot be appreciated fully in images is the dynamic feeling of the floating shells. The mood and feel of the room change with natural and artificial light; this is noticeable when simply walking through the space. Unlike any other flat or moulded wall treatment, the floating copper shells speak to the room.
These sculptural walls on the inside of one of the most important libraries in the country is a wonderful way to celebrate the history and beauty of patinated copper that spent 50 years on the roof of 180 Wellington St.
Silvio Baldassarra, OAA, FRAIC, is chairman of NORR Architects and Engineers. He has been the executive architect on some of NORR’s largest projects, including 180 Wellington St.in Ottawa, a $300-million rehabilitation of a heritage building. The Wellington Building has won 13 design awards to date. The copper sculpture wall for the parliamentary library in the Wellington project won the 2017 North American Copper in Architecture Award. Baldassarra can be reached via e-mail at firstname.lastname@example.org.
Source URL: https://www.constructioncanada.net/salvaged-copper-adds-drama-to-library/
Copyright ©2021 Construction Canada unless otherwise noted.