Achieving Energy Efficiency and Transparency with Double-Skinned Façades

Two is better than one.

At least that’s the case when it comes to these double-skinned façade projects, which help architects and designers tackle two goals with two layers. Double-skinned façades allow the building to maintain a level of transparency while still achieving the desired energy efficiency. Some even provide an active solution, having the ability to adapt in response to the environment changes. As a result, double-skinned façades are emerging as an option for achieving high-performance buildings. In addition to performance, several architects have praised the ability to maintain transparency with a double-skinned façade. Coatings and performance features that might decrease the desired aesthetic, can be placed on the inner layer of glass while the outer layer of glass can maintain the original design appearance.

Double-skinned façade projects are popping up all over the world, especially as countries continue to increase their efforts to achieve net-zero emission buildings. Here’s a glance at a few recent projects.

The MacKimmie Complex Redevelopment

Calgary, Alberta, Canada

This renovation by architect Dialog Design on the University of Calgary’s campus aims to create a net-zero building from the existing library building through a significant rebuild, renovation and expansion of the three-part structure. The project, comprised of the tower segment and the block and link segment, is a combination of single glazing laminated glass and triple glazing argon filled glass units fabricated by Tvitec with Hueck thermally broken custom frames and installed by Ferguson Corp. Transsolar Klimate Engineering provided the energy modeling, calibrating the coating and glass U-values, solar heat gain coefficient (SHGC), shading coefficient (SC) and visible light transmittance (VLT) for each context and orientation to optimize performance.

With an approximately 47-inch cavity between the two façades, the tower uses a chain-driven window ventilation system. Periodic doors were placed along the inner façade with suspended floor grating to allow access to the automated shading system for maintenance.

The block-and-link segment reverses the condition of the tower, using triple-layer glass on the exterior skin and single laminated glass on the interior.

“… A double façade with integrated automated shading was selected to provide the building with a dynamic jacket, to allow maximum solar access, provide natural ventilation, and to activate the exposed thermal mass of the concrete structure,” says project architect John Souleles. “The cumulative effect is that we are able to significantly reduce energy consumption.”

According to Souleles, the project incorporates an angled façade and triangulated corners and tapers, as well as net-zero carbon emissions, and the use and reuse of thermal mass.

The project was completed in late 2019. The block-and-link segment is set to be completed in 2022.

22 Bishopsgate

London, England

This project is a closed-cavity façade designed by PLP Architecture. It’s similar to a double-skinned façade with all the energy efficiency and aesthetic benefits, but without the need for maintenance to the cavity, according to Johannes Schwenk, senior project manager with Josef Gartner, a Permasteelisa company, responsible for the façade installation. Instead, he says, the cavity is sealed with clean, dry air.

The inner skin is an insulating glass unit consisting of an outer heat strengthened glass and an inner laminated annealed glass unit with medium-low iron Clearlite. The exterior skin is a laminated glass unit consisting of annealed glass with low iron Clearvision, both manufactured by AGC Interpane.

The inner coating is a low-E Iplus Advanced 1.0 for thermal comfort while the outer coating has Ipasol Bright White sun protection to reduce heat build-up in the cavity. The cavity depth is approximately 6.3 inches driven by the desire to maximize the usable floor area.

According to Alex Cox, Permasteelisa North America’s marketing communications manager, a closed cavity double-skinned façade was used to achieve high thermal performance while not consuming too much valuable floor space.

“A closed-cavity façade was chosen because it achieves the target U-value and SHGC by virtue of the blinds protected within the cavity,” says Cox.

While maintenance is significantly reduced due to the closed cavity design, occasional access to the cavity for blind replacement or other service is necessary. In order to allow for this, a “shuffle glazing” detail was added where the glass can be raised by 40 mm from the sill position.

Set for completion in March 2020, this building is designed to be the tallest building worldwide with a closed-cavity façade system, according to Cox.

Le Cristallin

Boulogne-Billancourt, France

This office space is a renovated project by architect Atelier Zundel Cristea (AZC) with glass fabricated by Tvitec. The double-skinned façade uses Guardian Sun-Guard Silver 70 coated solar control glass providing a high light transmission of 70% combined with a solar factor of 72%. The French company Goyer handled the glazing installation.

The project received Haute Qualité Environnementale (HQE) certification in recognition of its high environmental quality for both Renovation and Exploitation.

Kyra Thompson is an editorial assistant for USGlass magazine.

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