Invert Auto-Shading

Daylighting Performance and Visual Comfort Analysis of Dynamic Thermostatic Bimetal Shading



Photo of Jae Yong Suk

Jae Yong Suk

Assistant Professor

University of Texas at San Antonio

Photo of Doris Sung

Doris Sung

Associate Professor

University of Southern California



Allowing sufficient amount of natural light while avoiding excessive sunlight penetration is often hard to achieve with static facade systems due to constantly changing outdoor environments such as sky conditions and sun’s positions in relation to building facade orientations. In order to maximize daylighting performance and occupant comfort, dynamic properties of thermostatic bimetal (TBM) to curl in response to changing temperatures was adopted in a newly developed dynamic shading system, InVert™ Windows. As the TBM surface temperature from direct solar radiation increases, TBM pieces between the panes of glass change their shape to block the sunlight away from the building, resulting in shading building’s interiors. When the sun moves away from a respective window and the temperature of the individual pieces decreases, the TBM pieces revert to their original shape and position to allow more diffused skylight into a building. The system maintains outdoor views while TBM pieces change their shapes and positions.

The paper studies daylighting performance and visual comfort achieved by the dynamic shading system using TBM. A simple shoe box (4.0m x 6.0m x 2.5m) building with a full height south facing glazing and dynamic shading system was modeled in Rhinoceros. The following daylighting and visual discomfort metrics were used for performance evaluations: 1) Spatial Daylight Autonomy for annual daylight sufficiency, 2) Annual Sunlight Exposure for excessive sunlight penetrations, and 3) Daylight Glare Probability for visual discomfort. Luminance distribution of various TBM configurations on the interior space was the focus of this investigation. The simulated Spatial Daylight Autonomy and Annual Sunlight Exposure results show that the system successfully blocks excessive sunlight penetrations while redirecting natural light deep into the space. The calculated Daylight Glare Probability scores and luminance distributions confirm that the system greatly relieves potential discomfort glare issue of occupants while allowing direct view to outside.


Daylighting design can save building energy consumption and improve occupant well-being when building envelope systems are effectively designed and controlled. High performance building envelope systems help achieve daylighting benefits by

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In order to maximize daylighting performance and occupant visual comfort, dynamic properties of thermostatic bimetal (TBM) to curl in response to changing temperatures was adopted in a newly developed dynamic

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A virtual model was built in Rhinoceros software as shown in Figure 4. A closed room with 4.0 m wide x 6.0 m long x 2.5 m high was modeled

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Hourly based daylighting simulations were conducted for an entire year by utilizing a weather data file.

spatial daylight autonomy

Spatial Daylight Autonomy analysis was conducted for three different conditions: 1) without TBM

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Conclusion and Future Work

Shading performance of TBM shading system was tested in depth by various daylighting simulations. Daylighting availability and occupant’s visual comfort were simulated for three different conditions: 1) without TBM shading

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The authors appreciate Nathan Flores, a UTSA graduate student, to create a virtual model in Rhinoceros and to perform annual daylighting simulations.

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