Jump to navigation Jump to search This article is about comfort zones in building construction. The human body can be viewed as a heat engine where food is the input energy. Thermal neutrality is maintained when the heat generated by human metabolism is allowed to window versus portable air conditioner, thus maintaining thermal equilibrium with the surroundings.
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It was developed using principles of heat balance and experimental data collected in a controlled climate chamber under steady state conditions. The PMV model can be applied to air-conditioned buildings, while the adaptive model can be generally applied only to buildings where no mechanical systems have been installed. There is no consensus about which comfort model should be applied for buildings that are partially air-conditioned spatially or temporally. ASHRAE Standard 55 can be freely performed with the CBE Thermal Comfort Tool for ASHRAE 55. Similar to ASHRAE Standard 55 there are other comfort standards like EN 15251 and the ISO 7730 standard. Satisfaction with the thermal environment is important for its own sake and because it influences productivity and health. Office workers who are satisfied with their thermal environment are more productive.
Thermal discomfort has also been known to lead to sick building syndrome symptoms. Although a single static temperature can be comfortable, thermal delight, alliesthesia is usually caused by varying thermal sensations. Adaptive models of thermal comfort allow flexibility in designing naturally ventilated buildings that have more varying indoor conditions. Since there are large variations from person to person in terms of physiological and psychological satisfaction, it is hard to find an optimal temperature for everyone in a given space. Laboratory and field data have been collected to define conditions that will be found comfortable for a specified percentage of occupants. There are six primary factors that directly affect thermal comfort that can be grouped in two categories: personal factors – because they are characteristics of the occupants – and environmental factors – which are conditions of the thermal environment.
The former are metabolic rate and clothing level, the latter are air temperature, mean radiant temperature, air speed and humidity. People have different metabolic rates that can fluctuate due to activity level and environmental conditions. The surface area of an average person is 1. ASHRAE Standard 55 provides a table of met rates for a variety of activities.