Seven factors have been identified which affect man's response to the thermal environment. These are the dry-bulb or air temperature, water vapor pressure or relative humidity, the mean radiant temperature, air velocity, the physical activity and clothing of the occupant and the temporal characteristics of the exposure. During the past 16 years, the effects of these variables on thermal comfort have been studied extensively; however, in several experiments evidence has suggested that factors which may be considered as being "non-therma"" may also contribute to the thermal sensation.

Most noteworthy of these was a comfort study involving successive exposures to different temperatures. In this research, it was found that 22.2°C (72 F) in one environmental chamber was perceived to be colder than 22.2°C (72 F) in a second chamber. After determining that the thermal characteristics of both chambers were identical, the chamber that was perceived as being colder was modified by adding acoustical tiles to the ceiling, wood panelling to the walls, carpeting to the floor, indirect lighting and furnishing the interior with overstuffed chairs, pictures and end tables. Following this modification a different group of subjects was exposed to the 22.2°C (72 F) condition, and the responses of this group demonstrated that they were warmer than those of subjects who were exposed to the same temperature conditions before the modification. Moreover, when the responses of this group were substituted in the Comfort Model, it was estimated that the addition of the embellishments to the chamber was equivalent to raising the temperature 1.4°C (2.5 F).

This finding has widespread implications. First, it poses serious questions concerning the generalizations that can be made from thermal comfort studies that are conducted in a stark and somewhat sterile laboratory setting. This is not to imply that these studies are not valid nor reliable. Rather, the setting in which they are conducted is unrealistic and not at all like any interior space that might be experienced in everyday life. In short, these studies have ignored such factors as lighting, color, group size, room decor and other non-thermal features of the indoor environment.

For years artists, architects and interior designers have attributed moods and feelings to colors and lighting configurations. Helson lists such properties of color as texture, liveliness, pronouncedness, volume, gloss, hardness and warmth. As it relates to the latter dimension, Bennett and Rey failed to find support for what they called the "hue-heat hypothesis" which proposes that light frequencies toward the red end of the visible spectrum contribute to a feeling of warmth and frequencies toward the blue end of the visible spectrum contribute to cool feelings. Similar findings by Fanger concluded that because the "color of the surrounding surfaces had no influences on man's heat loss, any influence attributable to color would be psychological."

In probably the most comprehensive study of its type to date, and certainly the major stimulus for the present experiment, Flynn and Spencer evaluated the "subjective responses to colors of "white" light that are produced by commonly available electric light sources in interior spaces." Their results showed that the distribution of light in contrast to the color had a moderate influence in producing feelings of pleasantness . Aside from these conclusions, the findings demonstrated that various lighting configurations can create different feelings. Moreover, it is conceivable that they also could affect feelings usually attributed solely to the thermal environment.

In view of this, it appeared only logical to examine the effects of light and color on the thermal sensation. The purpose of this study was to study the interaction of lighting, color and temperature on the thermal response.