Use of wood for buildings is recommended in Japan to ensure the soundness of carbon dioxide absorption by forests. This new office building in the downtown area houses an indoor public plaza open to the public as a new attempt. This large space surrounded by timber has a light environment like an oasis in the town where anyone can relax for free throughout the day.

The wall and ceiling of the plaza with a 11 metre high ceiling are covered with carefully assembled wooden louvers. Multiple curves represented by density changes are reminiscent of a magnificent scenery of overlapping mountain ridges. The large timber wall in front is illuminated horizontally by the spotlights installed on the wind-resisting beam supporting the exterior glass wall. At the gaps between the continuous louvers, ultra-small one-watt LED upper lights are embedded to illuminate adjacent wooden louvers faintly where a gentle curve emerges. The shadows woven by the spatial-scale light that illuminates the wall surface boldly and the human-scale lights subtly incorporated into the wall evoke a sense of tranquil beauty like the moon peeking through mountains. The mountain-shaped bench in the center is symbolically highlighted by the spotlights from above. The spotlights installed between fine louvers elaborately never to be exposed on the ceiling look like the Milky Way floating in the night sky.

In the prefunction to the office lift lobby, ripple-pattern textured, mirror-finished stainless steel panels are installed on the whole wall, serving as a mirror reflecting the plaza. Downlights illuminate these panels from different angles, reflecting the ripples at your feet, which evoke the memory of the stream flowing through the mountains where the trees grew.

We use a lighting scene controller with an annual timer. Multiple scenes unfold while gradually dimming the lights from daytime when sunlight pours in through the large glass to night when artificial lights dominate. Even after 10:30 p.m., the building’s closing time, highlighting the wooden wall in the faint light contributes to achieving psychological safety in the cityscape late at night.

All the lighting fixtures use LED. Light sources with the optimum output are selected through a 3D simulation applying the measured reflectance of the wood. The architectural design also contributes to energy saving by laying out lights well-balanced with a small quantity of light in a space with a large air volume. Thus, we have obtained a ZEB (Net Zero Energy Building) Oriented certification demonstrating our contribution to carbon neutrality.

Recently it has become difficult to spend time outdoors due to global warming. Indoor plaza spaces maintained in a comfortable environment are in demand as resting places for travellers, families, and elderlies as well as lunchtime places for workers in neighboring offices, bringing liveliness.


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