一般认为，有六个主要变量控制任何给定结构1和2的乘员的舒适感。这些变量包括空气温度、相对湿度、空气流速、平均辐射温度、居住者的活动水平以及所穿衣服的数量。在过去的50年里，人们进行了实验研究，以确定这些变量之间的相互关系，以及其中一个变量的变化，以及其他变量的给定固定值，如何影响舒适度3、4、5、6、7、8和9。最近，在这些研究1、10、11和12中使用了经过过去一些实验验证的数学模型。在许多情况下，使用平均辐射温度（MRT）作为辐射环境对人体影响的单点指标是一个缺点。环境中特定点的平均辐射温度定义为一个假想的黑色外壳的均匀表面温度，测试点的一个小黑球将与该外壳交换与实际环境中相同的辐射能量。 换句话说，它是一个单一的温度，作为一个平均效应给出了整个辐射环境的指示。它没有显示特定环境的不对称方面。引文:ASHRAE交易，第82卷，第2部分，华盛顿州西雅图

It is generally accepted that there are six primary variables that govern the feeling of comfort on the part of occupants of any given structure1 and 2. The variables are air temperature, relative humidity, air velocity, mean radiant temperature, the level of activity of the occupant, and the amount of clothing worn. Experimental work has been done over the past fifty years to determine the interrelationships among these variables and how a change in one, with given fixed values of the others, affects comfort3, 4, 5, 6, 7, 8, and 9. More recently, mathematical models which have been verified by some of the past experiments, have been used in these studiesl, 10, 11, and 12.The use of mean radiant temperature (MRT) as a one-point indicator of the effect of the radiant environment on a human subject is in many cases a shortcoming. The mean radiant temperature at a specific point in an environment is defined as the uniform surface temperature of an imaginary black enclosure with which a small black sphere at the test point would exchange the same energy by radiation as it does in the actual environment. In other words, it is a single temperature that gives an indication of the entire radiation environment as an averaged effect. It gives no indication of asymmetrical aspects of the particular environment.