A high performance building needs to optimally satisfy human comfort, environmental concerns, energy efficiency, and economy. In order to achieve this collective goal with a minimum compromise among these four sustainability parameters, buildings need to reduce their exergy demand besides energy demand. In the so-called low-exergy buildings, the radiant to convective split of heat transfer between the human body and the indoor space, which affects human body exergy loss need to be optimally controlled by radiant and convective systems working together. In this process the indoor air exergy and wall exergy become crucially important with respect to economy, environment, and energy. The radiant to convective split also modifies the operative temperature calculations in such a manner that normal thermostats may not be used. Therefore, while building industry is moving towards low-exergy, high performance buildings, accurate and adaptive operative temperature sensors become a real necessity rather than a luxury. All these require an accurate yet practical operative temperature sensor. Existing operative temperature sensors are either impractically sophisticated, expensive, and designed for laboratories, or inaccurate for everyday life. Additionally, their calibration and dynamic response do not adequately encompass important variables like the indoor space size, altitude, activity level, clothing, body position, latent to sensible body loads, human body exergy loss, and air velocity. In this study a new, practical and real-time responsive operative temperature sensor algorithm and prototype was designed, which may be easily calibrated in the ANSI/ASHRAE Standard 138 Test Chamber for all variables involved, and then precisely and dynamically corrected in the field with the same algorithm. This paper explains the basics of new sensing and correction algorithm and presents the details of the prototype. A discussion follows about its impact on low-exergy building operation, energy savings, economy, and environmental footprint.