Analysis of an indoor environment with a hydronic floor-heating syste under the sensory index

Recent buildings are required to not only energy conservation but also healthy and amenity for residents. The active systems (radiant heating and cooling system, personal air conditioning system, etc.) and the passive systems (natural draft, solar heat gain, etc.) for energy conservation are suggested to accomplish both performances. Therefore, the quantitative estimation including human sensation of hygrothermal environment and energy performance based on these systems is important. Generally simulation software to predict temperature, humidity, heating and cooling load of building spaces does not take into account of human sensation under non-uniform environment such as radiant heating and cooling system. THERB is dynamic simulation software that can estimate temperature, humidity, the sensory index, and the heating and cooling load for multiple-zone buildings and wall assemblies. The heat and moisture transfer models used in THERB, such as those for conduction, convection, radiation, and ventilation (or air leakage), are based on detailed phenomena describing actual building physics. These models can be applied to all forms of building design, structure, or occupant schedules. All of these phenomena are typically calculated without simplifying the heat and moisture transfer principles of any building component or element. Thus, THERB can predict the hygrothermal environment of the whole building, taking into consideration the complex relationship between heat and moisture transfer and airflow. This paper explains the prominent features of the calculation models, and investigates the accuracy of THERB by comparison with a test house equipped with a hydronic floor-heating system. It was found that THERB could predict the thermal environment of a room equipped with a hydronic floor-heating system with absolute accuracy. Subsequently, the sensory index "COMSET^∗," based on the hygrothermal balance of the various parts of the human body, is calculated in case of the non-uniform thermal environment of floor heating, with a combination of THERB. Sensitivity analyses of the heating system and the sensory index provide the following results. 1) Even if the values of COMSET^∗ remain constant, the room air temperature rises when the heating system is changed in the following order: space conditioning, floor heating in a standing position, and floor heating in a sitting position, to cause a sense of warmth. 2) The floor-heating system has the ability to decrease the heating load dramatically, depending on the physical posture, if the radiative heat and the contact thermal conductance from the floor for each part of the human body are realistically considered as control requirements of heating.