( Rinnai ) Remote controller BHY-15 BHY-16

An Intuitive Bath Controller for Everyday Living

Working in close collaboration with Rinnai’s in-house design team, I led the product design of the Rinnai Remote Controller BHY-15 / BHY-16, overseeing not only the industrial design but also the interface design, operation sounds, and voice guidance to shape the entire user experience.As an interface that people interact with many times each day, the product was meticulously designed to achieve exceptional legibility, intuitive usability, and refined tactile and auditory feedback, while maintaining a calm, architectural presence that naturally integrates into contemporary living spaces.Rather than focusing solely on functionality, we designed a seamless experience that extends from the moment of interaction through every stage of use. The result is a product that embodies Rinnai’s philosophy of functional integrity and enduring craftsmanship (“Shitsujitsu Goken”) in everyday life.

Functional Integrity and Enduring Simplicity

Since introducing its first ceiling-mounted bathroom heater and dryer in 2000, Rinnai has continuously evolved the product beyond its original purpose of reducing the risk of heat shock—the physiological stress caused by sudden temperature changes during bathing. New functions such as efficient laundry drying and mist sauna technology have transformed the bathroom into a more comfortable and multifunctional living space. This latest model incorporates a human-presence sensor, allowing the product to respond more intelligently to everyday life. As the system became more sophisticated, the remote controller required enhanced functionality and a clearer, more intuitive interface capable of communicating a greater amount of information without increasing complexity.

The design concept is rooted in Rinnai’s philosophy of Shitsujitsu Goken—a Japanese principle that values substance over ornamentation, combining simplicity, practicality, robustness, and well-being. Rather than pursuing visual novelty, the objective was to create a timeless design that integrates naturally into any home and remains relevant for years to come. The design language emphasizes clean horizontal and vertical geometries while eliminating unnecessary visual elements. A restrained monochromatic palette reinforces a calm, architectural presence that avoids visual noise within the living environment.

The upper half of the controller is dedicated to a black display area, consolidating key information and primary controls to improve legibility and ease of use. Only the information required for the current operation is illuminated, while all other indicators remain hidden. This “blackout” approach minimizes visual distraction and ensures that the product maintains a refined, unobtrusive appearance even when not in use. By refining both functionality and form, the design supports everyday routines—from bathing to household chores—while creating a more comfortable, reassuring, and elevated living experience.