INSIGHTS

2023.05.11

R&D WORKS Vol. 25

JAPAN SPORT OLYMPIC SQUARE ──Wave-shaped slit louvers

An architectural envelope that controls shading and daylighting.

R&D WORKS TOP

There is currently a great deal of attention being paid to technology that improves the environmental performance of the building envelope, that is, the boundary between indoors and outdoors, including exterior walls. The idea is to give the walls themselves the power to improve the environment, rather than forcibly improving the environment while consuming energy. One notable example is the use of louvers to block sunlight. However, there is a dilemma in that the more heat rays are blocked, the less illuminance is obtained from natural light. This issue was resolved by innovating the louver shape, resulting in the wave-shaped slit louver. This technology, in which the exterior design itself improves environmental performance, has been realized in a complex building.

East side exterior. Louvers are angled along the gentle curve of the exterior.
A design that gives a sense of fluctuation.
Exterior view from the north-northeast side.
The north facing glass curtain wall
The shape has a twisting, upward-lifting feel.

Light-blocking louver design

JAPAN SPORT OLYMPIC SQUARE is a long building stretching from north to south, with large exterior walls rising on both the east and west sides. Both sides are constructed with fully glass curtain walls, and we considered installing louvers to improve light blocking. As the sun's altitude increases, the angle of the louvers to the wall becomes shallower, so vertical louvers are effective for installation on the east and west sides. Vertical louvers are used here as well. However, if all the sunlight is reflected, there will not be enough light inside the room, and we will have to rely more on artificial lighting. Therefore, slits are made on the surface of the louvers to let in natural light. Direct sunlight is reflected, while the light reflected by the slits is taken in as indirect light, increasing the brightness on the back of the louvers. The shape and design of the louvers alone gives the building envelope the ability to control light.

The louvers seen from the inside.
The light is diffused within the corrugated slits,
This increases the brightness of the surfaces visible inside.
Small louvers obstruct the view,
Each sheet is large, measuring 400 x 3850 mm.

Cross-sectional shape simulation

The slits have a gentle wave-like shape that gives a sense of flow and movement. As the headquarters of an athletics-related organization, they express the movement of "sports" and are an important design point that determines the impression of the exterior, but at the same time, they are also a technology that improves environmental performance. The shape of these slits was obtained through repeated studies and simulations of light reflections using the movement of the sun as a parameter. The slits undulate, gradually changing from wide to narrow; if they are too wide, light will leak out, and if they are too narrow, the amount of light taken in will be insufficient. This also changes depending on the cut angle, and the shape was optimized by inputting the sun's profile angle 365 days a year.

Of course, the width of the louvers themselves, the installation angle, and the installation intervals were all quantitatively studied in terms of daylighting.Furthermore, the exterior design was determined by judging the physicality as well, so as to ensure sufficient visibility to the outside without obstructing the view from inside the building as much as possible.

The louvers are made of GRC (glass-reinforced fiber concrete), and the complex shapes are created by pouring GRC into a mold.

A sketch from the idea stage. Using this as a basis, we used Grasshopper®︎ to verify the angle at which light could be captured while blocking direct sunlight.
From the annual solar altitude information,
Calculate the time facade is exposed to sunlight,
Analysis results comparing the presence and absence of slits.
By providing a slit,
The brightness of the louver surface on the indoor side is higher than that without slits.
It was found that the increase was 1.8 to 3.3 times.
Louver formwork (left) and finished louvers (right).
It was made from GRC (glass fiber reinforced cement), which is lightweight and has excellent formability.

[Patent registration] Registration number: Patent No. 7270492

Please see our website for an introduction to JAPAN SPORT OLYMPIC SQUARE project.
For patent information on this louver, please click here.
(Access the patent information platform/J-PlatPat)

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JAPAN SPORT OLYMPIC SQUARE ──Wave-shaped slit louvers

An architectural envelope that controls shading and daylighting.

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Update : 2019.01.17

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