3.1.3 The preference for variation in temperature
EN ISO 7730 (ISO, 2005) is based on climate chamber studies. They show that people basically have the same thermal preferences, regardless of where they live on earth (de Dear et al., 1997). This philosophy for evaluation of thermal comfort is based on the assumption that neutral is the optimal status for thermal comfort. However, a constant temperature without variation during the day may not be what humans really prefer. Studies show that we tend to prefer variations in temperature, and that changes in around the neutral temperature is experienced as pleasurable. (de Dear, 2006).
As human beings, we may in fact want variations in our thermal environment; we have a need for sensory and physical stimulation. One way to achieve is with fluctuating interior temperatures to counteract “thermal boredom” (McIntyre, 1980; Kwok, 2000). Heschong (Heschong, 1979), argues for environments with physical variations rather than static conditions, describing comfort as a relationship between thermal contentment and human imagination. We as humans are capable of recognising, remembering, and adapting ourselves to most thermal experiences.
3.1.4 Adaptation to a warm climate
At the same time, field studies show that people working in naturally ventilated office buildings in warm climates accept higher temperatures (de Dear and Brager, 1998). The standard EN 15251 (CEN, 2007) provides limits for acceptable indoor temperatures for naturally ventilated buildings. These temperature levels assume that people can freely adapt their clothing and operate windows. Based on the outdoor 'running mean' temperature during the previous week, acceptable indoor temperatures are found in Figure 3.1.3. A running mean is a weighted average of a time period where the latest time periods has the greatest weight.
In residential buildings, it can be assumed that the occupants will adapt their clothing to obtain comfort and in buildings with VELUX roof windows they will operate the windows, which were the assumptions for using the adaptation method.
The consequence of adaptation is that thermal comfort can be achieved in warm climates, without air conditioning, by using natural ventilation, solar shading and intelligent building design. This allows significant reductions in energy use (see section 5.6.5