Untold Proposals for the Future – Nikken Sekkei's Professional Services
Part 2: Creating New Social Value Through Facade Engineering (Part 1)

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To propose new approaches to architecture with higher resolution by utilizing cutting-edge digital technology, Nikken Sekkei established the Digital Engineering Lab (DEL) in 2022, a group of engineers that leverages its extensive design experience and high level of expertise to provide technical proposals and design support.

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At DEL, five specialized teams provide technical proposals and design support for new and interdisciplinary design technologies required in modern architectural design and urban planning.

One of the services DEL provides is architectural facade design based on advanced analytical technologies. A facade serves as a mechanism for controlling the external and internal environments, and the way it is constructed affects the internal environment—including temperature, illuminance, and views.Furthermore, the shape of a facade has a significant impact on the landscape and the surrounding environment. To create facades that are both environmentally sustainable and aesthetically sophisticated, DEL continuously develops innovative solutions that span the fields of design, structure, building systems, the environment, and construction.
We spoke with Keishiro Tachi (Design & Technical Department, Tech Design Group Director), who leads facade engineering and environmental computational simulation at DEL, about the originality of Nikken Sekkei’s facade design and the social value it brings.

Optimizing views of the sky and greenery to maximize the value of a place—a new concept called "sky and green view ratio"

🄫Akira Ito [aifoto]

The Midosuji Daibiru, completed in 2024 in the heart of Osaka, required not only high environmental performance but also added value for users. Nikken Sekkei proposed a building envelope design that would take advantage of the site's excellent views. With the lush Namba Shrine to the south and the beautiful ginkgo-lined Midosuji Avenue to the east, what strategies could be employed to achieve the best possible views while minimizing the load of sunlight?

Here, DEL's facade engineering team developed a new method called "sky-green view ratio." This unfamiliar "sky-green view ratio" is a numerical representation of the ratio of the area of "sky" to "greenery" that falls within a person's field of vision. DEL has applied and developed the concept of the sky ratio, which is common in architectural design. General-purpose software such as Rhinoceros and Grasshopper are used for the analysis, but DEL's unique programming allows for the quantification of the "view" specific to each location.

Using this original technology, the facade design for "Midosuji Daibiru" was developed as follows:

"Sky and Green View Ratio," a numerical representation of the area of sky and greenery. Bottom right: ©Akira Ito [aifoto]

Even within the same building, the view differs depending on the direction and height. Therefore, we first quantify the proportion of sky and greenery visible from every point in the building and map it onto the wall surface as "view potential."

"Sky and Green View Ratio" quantifies the area of sky and greenery, and shows the "view potential" of each window surface using color coding.

Typically, facade design presents a dilemma: to obtain a view, it's impossible to completely block out sunlight. This is because fewer windows are better for reducing heat load, while larger glass surfaces are advantageous for maximizing views.
Therefore, using "view potential" as a criterion, we used computer simulations to examine the depth and angle of the louvers (fins) for sun shading. As a result, in locations where the view was not very good to begin with (low view potential), we increased the number of louvers and increased their depth to reduce the environmental impact. On the other hand, in locations with high view potential, we reduced the number of louvers and made them shallower to create an indoor space with a good view.

This design approach combines viewing potential with sun-shading fins (louvers) to reflect the contradictory needs of environmental performance and scenic views in the exterior design.

DEL repeatedly ran this complex simulation, examining the facade together with the designers. However, Tachi's view remains that "the optimal solution cannot be obtained by computers alone."
Therefore, we further checked the exterior view and interior views using computer graphics. Ultimately, we narrowed down the options from a comprehensive perspective, including not only design considerations but also cost adjustments by reducing the amount of building materials used.

By combining horizontal and inclined fins and positioning them appropriately according to orientation and height, the target environmental performance is ensured for the entire building. ©Akira Ito [aifoto]

Based on considerations regarding the ratio of sky and greenery views, the result is a diverse facade and office workspace that maximizes the comfort of each individual area, rather than creating a homogeneous space like that of modern architecture.

This sky and green view ratio is a tool that can also be applied to urban public spaces. By evaluating how the sky and greenery are visible, it can contribute to creating more comfortable spaces. At Midosuji Daibiru, the sky and green view ratio was used to evaluate the views from the lower floors facing Midosuji Avenue. As a result, a pleasant terrace with plenty of greenery was created.

Based on the ratio of sky and green spaces, views from pedestrians and terraces were visualized. By increasing the green space ratio in the lower floors where the sky ratio is low, the value of the urban space was also enhanced. ©Akira Ito [aifoto]

Keishiro Tachi

Tech Design Group, Design & Technical Department
Director

After completing his graduate studies at the University of Tokyo, he joined Nikken Sekkei in 2009.
His specialty is environmental engineering. From the time he joined the firm until 2016, he was a member of the Building Services Division (Architectural Design Department), where he was responsible for mechanical systems design, primarily for office buildings, including the Kyobashi Edogrand (2016) and the Toa Road Industry Headquarters (2015).
Since 2017, I have been working in the Facade Engineering Department, conducting environmental engineering for the facades of buildings and public spaces both in Japan and overseas.

Utilizing digital tools, I carefully analyze the climate and environment of each region and site, striving to propose facades that create spaces that are both comfortable and appealing to both viewers and users.

Keishiro Tachi

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