The Butterfly

Providing a unique and integral cladding/envelope solution suited for high-rise buildings has been an inherent challenge for this building typology since its conception. The progressively stringent energy codes and development policies (i.e. Vancouver’s new Energy Step Code, the Higher Buildings Policy, Large Sustainable Sites, and the Green Building Policy) demand an evolution of facade technology and practices. Coupled with advanced performance requirements, Architects are also challenged to incorporate culturally relevant design solutions to meet heightened aesthetic demands. This case study examines the facade system developed for the Butterfly tower in Vancouver, BC, detailing the innovations of the system, the process of development, and challenges faced.

The skin of the main tower consists of double-wythe, insulated, precast concrete panels and unitized, insulated ribbon windows structurally supported by the panels. The precast panels are geometrically complex: curved in plan to suit the tower’s cylindrical massing, undulated in elevation to offer unbounded views and bulged outward to form a dynamic urban expression while providing exceptional envelope performance. The envelope’s complimentary ribbon windows are similarly complex, curved in both plan and elevation.

In contrast to conventional exterior wall assemblies with discrete interior and exterior components, this uniquely integrated system condenses the entire assembly—interior finish, insulation, waterproofing, exterior finish and supporting structure—into a single entity, establishing material continuity between the exterior and interior.

In doing so, this innovative approach aims to simplify construction and sequencing to effectively minimize the time and cost required to deliver a finished exterior wall assembly. However, because all of the components are assembled before arriving on site, the need for precision in building construction is heightened, frontloading the design, testing, and manufacturing processes. To achieve the great geometric complexity without compromising performance and benefits of the sandwich panels were especially challenging in this respect.

Hence, this progress report focuses on the study of mock-ups for this unique envelope system. It’s believed that this experience would provide a reference for future developments in both facade design and the construction industry at large.