Window in Wall: Back to the Future



Photo of Thomas Auer

Thomas Auer

Technical University of Munich (TUM)

Photo of Ata Chokhachian

Ata Chokhachian

Research Associate

Technical University of Munich (TUM)


In order to get to a carbon neutral building stock – which is e.g. required by the EU Carbon roadmap by 2050 – our efforts need to be smart and holistic on all scales of design. At the same time, it is essential that a transformation process leads to healthy, comfortable and inspirational environments – indoors as well as outdoors. Additionally, it is necessary to re-think the approach towards environmental quality. Over the past decades a steady state and homogeneous environment was considered comfortable and glass buildings became international style. In order to deal with the problems of all glass buildings, facades solutions and mechanical systems became sophisticated machines, which adapt to the constantly changing outdoor environment. Building controls, sensing and actuators became crucial for a comfortable and somehow energy efficient operation. However, more and more one recognizes that this approach doesn’t provide user satisfaction nor excitement. The complexity leads to an operation, which is extremely sensitive to so called uncertain boundary conditions and imperfection in construction and operation. As consequence, one can see significant performance gaps between design and real-world operation. That’s one of the reasons why New York City mayor Bill de Blasio, on April 2019 in a press conference announced a plan to ban construction of glass and steel high-rise buildings, in a major bid to tackle climate change. In order to decarbonize our buildings, it is essential to design buildings towards robustness and longevity. Robust optimization is a proven design method - used in other industries – which need to be adapted towards the needs of the building industry. A definition of uncertain boundary conditions allows to find a robust optimum. This leads to a building design, which is less dependent on systems, which are very likely to fail over a certain lifetime. Therefore robust optimized buildings aim for reducing the complexity in facade and mechanical systems design, which ultimately questions window to wall ratio.


Over the past decades, building design has gone through significant changes in order to increase energy efficiency, by means of architectural design and building technology. The performance of glass facades

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For a robust building design, buildings need to become less complex, less dependent on sensorics’, building controls and mechanical systems. Systems have to be considered supplemental to a rather passive

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Research Question

Following the framed hypothesis, this study addresses following questions in the domain of building design research and performance:

How does robust design methods impact building design – especially façade design?How could

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Robust Optimization vs. Climate Responsive Design

Over thousands of years architects have been using climate responsive design strategies, considering the challenges and opportunities of a local climate (Krishan 2001). Climate responsive design had been fundamental for

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Case study for a climate responsive design

Manitoba Hydro (KPMB with Smith Carter Architects) became an exemplary building, which illustrates climate responsive design (Figure 1). This was the result of an integrated design process, which included architects

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Case study for a robust optimized design

Robust Optimization is one of the commonly used methodologies to approach multi-objective problems. It is a modeling method, combined with computational tools, to solve optimization problems where the data are

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The built environment is more than the physical building. A transformation of our built environment and a decarbonization of the building sector require strategies which can only be accomplished by

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Rights and Permissions

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