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Thinking outside the Comfort Box

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An understanding of human thermal comfort has proven to be one of the key components of energy efficiency in buildings. Human comfort is more to comfort than just temperature and humidity. For instance, the radiative energy that is emitted from walls, the air speed and also physiological factors such a as the people’s metabolic rate, the skin wettedness, and skin emissivity all have an effect.

Maintaining the thermal comfort of building occupants, it is both at the basis of energy efficiency as well as a challenge; a negotiation between air-based heating and cooling systems that rigidly maintain supply air temperatures and humidity levels. Such a practice overlooks several other design variables, including the mean radiant temperature, which is responsible for a significant portion of an occupant's thermal comfort, or air velocity.

Deciding where system setpoints should be for systems that go beyond simple air based cooling is difficult to arrive at through intuition and current metrics, as the inclusion and modulation of other thermal comfort variables such as air velocity, skin temperature, skin wettedness and metabolic rate are not entirely independent variables.

 

This tool for assessing a new radiant cooling system compares heat loss through primary modes of heat transfer generated by an occupant's metabolic rate, including air temperature and relative humidity as the relevant independent variables for thermal comfort. As such it can be used for designing a new radiant cooling and natural ventilation systems that do not change the air temperature or humidity to provide comfort.

 

This web application was put together to aid the design of more comfortable spaces. It's the all-new psychrometric chart - now in colour. In the online psychometric chart, the users’ goal is to match the colorbar condition to the plot.