Installing Outdoor Ofuro Tubs for Traditional Bathing Experiences Japanese ofuro tubs need a deep chin down soak which means the tub is deeper than the ordinary bath tubs. Traditionally, Japanese soak in hot water heated by quiet non-electrical wood fired heaters. They have thick cedar construction which means the tub will be able to maintain heat much longer than others. Northern Lights Ofuro tubs are manufactured from clear western red cedar, which is considered as a close cousin to the traditional cypress wood used in Japan. But red cedar offers amazing benefits as it is naturally resilient to bacteria and decay. It’s chosen for its high insulating value.