A Double Skin Facade System: Transparency in the Age of Building Energy Use Reduction

William Rawn Associates is a leader in the use of double skin curtainwall systems, with a growing collection of built projects. While the first double skin façade dates to 1903 in Germany, application has only gained traction in the US recent years. This passive design strategy involves a two layered façade with cavity that can both insulate from cold and mitigate heat.

Before embarking on use of this innovative system, we visited multiple buildings in Germany and the UK to study how best to adapt the technology to a building’s specific needs, keeping operational concerns paramount. This research allowed us to understand the potential of the system to provide a highly transparent and energy efficient façade, with thermal comfort, glare control, and maintainability. It was clear that while not common in the US, double skin technology was a proven system, in successful use in Europe, and with great potential for use in the US.  

Our first double skin curtainwall was at Cambridge Public Library, completed in 2009. CPL was the first US project to incorporate all key ingredients of advanced European double-skin curtainwall technology. A multi-story 180’ long, 3’ deep cavity allows for natural convection with efficient heat capture and exhaust while enabling maintenance access. Lightweight motorized aluminum sunshades in the cavity, tied to the building management system, provide glare protection and shade.  The cavity’s exterior glazing is point-clamped monolithic glass, while interior glazing is insulated glass. Large translucent glass exterior shading canopies serve as light shelves.

In Winter, air inlets at the bottom and top of the cavity are closed to create a thermal buffer, insulating the interior.  In summer, low vents are opened to admit cool air, which rises by stack effect as it warms, to be vented at top. In Fall and Spring, cavity temperature is maintained with operable windows.  The double skin façade is CPL’s key design element. Its transparency is an open welcome to the community, with its visual continuity with the adjacent park. The double skin reduces energy use by 50% compared to conventional curtainwall, providing thermal comfort in reading spaces.

Following the success of this initial project, we introduced double skin technology to Harvard Business School’s Tata Hall, completed in 2014. The double skin significantly reduced the building’s energy use without compromising the transparency so important to its design, which was enhanced with the use of highly transparent low iron glass. Tata Hall’s double skin curtain wall modulates heat loss and heat gain for thermal comfort, allowing visitors to comfortably sit next to the glass in winter. The three-foot air cavity reduces the building’s peak cooling load by 71% and peak heating load by 21%, resulting in a 51% more energy efficient building. Within the cavity, motorized horizontal louvers are controlled on a sun sensor, reducing low-angled solar glare and heat gain to create a comfortable interior.

These early applications of double skin design were followed by other notable applications.

Penn State Recital Hall, completed in 2018, employs a two-story double skin curtainwall for not only for thermal benefit, but also for acoustic performance. The curtainwall is located directly in the recital hall. The cavity is mechanically vented, with thermal glass on the exterior and monolithic glass on the interior.

John’s Hopkins School of Nursing, completed in 2021, introduces double skin curtainwall in the prominent two story “study cube”. This simpler version of a double skin façade is based on a European model, without operable louvers at the base of the cavity.

At University of Virginia, Ruth Caplin Theatre we employed a compressed version of double skin façade. 

We continue to incorporate double skin technology in recent work. The design of RIT Student Hall for Exploration and Development includes at double skin at the “Glass Box Theatre”. The design of VCU Arts and Innovation Academic Building also has a double skin in the Innovation Studio, Concert Hall, and Ensemble Studio.

William Rawn Associates is an early adopter of double skin technology and has continued to incorporate it into multiple projects over the years. It has been a successful means of achieving energy efficiency together with transparency, enhancing visual connections with the exterior, and creating environmentally responsible, open, and welcoming places.