This paper describes the design, implementation, and user evaluation of an IoT project focused on monitoring and management of user comfort and energy usage in office buildings. The objective is to depict an instructive use case and to illustrate experiences with all major phases of designing and running a fairly complex IoT system. The design part includes motivation and outline of the problem statement, the resulting definition of data to be collected, system implementation, and subsequent changes resulting from the additional insights that it provided. The user experience part describes quantitative findings as well as key results of the extensive human factors study with over 70 office users participating in two major pilots in France and Japan. The original idea for this project came out from a diverse group of companies exploring challenges of designing and operating smart buildings with net-positive energy balance. Members included companies involved in the design and construction of smart buildings, building-management and automation systems, computer design, energy systems, and office furniture and space design. One of the early insights was that maximum energy efficiency in office buildings cannot be achieved and sustained without the awareness and active participation of building occupants. The resulting project explored and evaluated several ways to engage and empower users in ways that benefit them and makes them the willing and active participants.