A curved slab works as a chimney to generate ventilation, and as a bench to let people relax Maruhon Ryokan is a traditionalJapanese-style hotel in Sawatarihot-spring, Gunma, since 1600s. The bathhouse has ordinary form with gable roof, though a curved slab separates the interior to the bathroom on the lower floor and the rest space on the upper floor.

In the bathroom, people can enjoy the silence of the space and the transparency of the spring water, due to the curved slab-chimney which generates buoyancy-driven ventilation without fan and diffusion of lights.

And at the same time, this curved slab is used as the backrest of a big bench on the upper floor which lets people to take a rest after bathingby feeling the outside view and wind from the big window.

We decided the form of the curve by finding balance between the CFD (Computational Fluid Dynamics)simulation of the air circulation and the coziness as a backrest.

The elements for creating comfortable environment, as light, air and view, are combined by a curved slab, and a rich comfortableness is generated into a small bathhouse.

Sustainable renewal This project started from considering where of the old Japanese-style hotelto invest to pull in more guests and to effect on long term, answering to the consult for renewal by the client. In this term, we renovate 20m2 small area.

The area is thought to be the most effective point to invest, because it is a node of access to the existing big bathhouse and the outside bath, and also has unused potential of the view to the west.

Not with major renewal taking a risk of investment but with minor and gradual renewal adding small architectures to innovate the image, we plan to enhance the sustainability of the long-established hot-spring hotel.