My origins as a researcher lie in a paper written by a mentor I met during my postgraduate studies. That paper, filled with mathematical equations, struck me as more beautiful than the design drawings I had produced myself, and the desire to ‘write a paper like this’ became the catalyst that set me on my current research path. Since then, I have devoted myself to building physics based on heat transfer theory, heat and mass transfer theory, and thermodynamics, consistently adhering to a research approach that involves ‘explaining the physical phenomena occurring in buildings through theory, expressing them rigorously as mathematical models, and solving them using computers’.

The culmination of this work is the building thermal environment analysis software ‘THERB for HAM’. Within a building’s structure (walls, roof, floors, etc.), heat and moisture move whilst influencing one another. The core of THERB lies in the fact that it precisely models this ‘coupled heat and moisture transport’ using the concept of moisture potential from non-equilibrium thermodynamics, and further extends this to the entire building as a combined transport of heat, moisture and air, including advection.

This research achievement, ‘A Series of Studies on the Prediction of Building Thermal Environments Considering Coupled Heat, Moisture and Air Transport’, was awarded the 2009 Architectural Institute of Japan Prize (Paper Category). Furthermore, this software has been certified by the Ministry of Land, Infrastructure, Transport and Tourism (Certification No. 141) as a specially evaluated software under the ‘Act on the Promotion of Quality Assurance in Housing’ (Article 53, Paragraph 4: Method for Calculating Annual Heating and Cooling Loads).

A major feature of THERB lies in its extremely high reproducibility and versatility, grounded in building physics. For example, it is equipped with the following functions.
Main Functions of THERB

• Coupled analysis of heat, moisture and air movement throughout the entire building (including the structure and multiple rooms) (high-precision HAM model)
• Air conditioning control based on temperature, humidity and PMV
• Accounting for the time-varying nature of heat and moisture transfer via convection
• Calculation of heat and moisture transfer coefficients (natural and forced convection) for each component based on dimensionless equations
• Geometric analysis of sunlight and shade on internal and external surfaces
• Multi-layer window model (solar transmittance accounting for multiple reflections and absorption between glass panes)
• Multiple reflection and absorption of transmitted solar radiation on interior surfaces
• Accounting for the non-linearity of radiative heat transfer
• Long-wave radiative heat exchange between interior surfaces
• Network airflow model (natural and forced ventilation)

As such, whilst THERB enables extremely high-precision analysis, its highly specialised nature has meant it has primarily been used for research purposes.

Against this backdrop, driven by a strong desire to see this simulation technology utilised by a wider range of designers and researchers, we have developed ‘ThermalOne’. ThermalOne adopts Rhinoceros/Grasshopper—widely used by designers worldwide—as its input interface. Furthermore, by integrating the visualisation software ‘THERB Viewer’, we have created an integrated environment that enables users to carry out everything from the creation of architectural models to the execution of simulations, and the analysis and visualisation of results.

This allows users to perform advanced simulations through intuitive operations whilst maintaining the physical rigour and analytical accuracy of THERB, evolving the tool into one that is accessible not only to specialists but to a much wider range of users.

ThermalOne is available in three versions—‘Standard’, ‘Professional’ and ‘Premium’—each with different features tailored to specific purposes. As of June 2026, the Standard version is available, with plans to release the other versions sequentially in the future.

As global warming progresses, the amount of water vapour in the atmosphere is increasing, and the risks of condensation and moisture damage are expected to become even more serious in the future. In such an era, the importance of precise thermal environment analysis, including moisture, is growing ever greater. We hope that ThermalOne can contribute, even in a small way, to the realisation of comfortable and energy-efficient buildings.