Updating the adaptive relation between climate and comfort indoors; new insights and an extended database

We look critically at the principal graphs relating thermal comfort indoors to the climate, and compare the metrics used for the climate; an exponential running mean of the mean outdoor temperature proves better than either the historic monthly mean or the current outdoor temperature. Using the SCATs and the ASHRAE RP-884 databases of field-studies we develop a method to derive a standard sensitivity to indoor temperatures change. People are more sensitive to temperature change within a single working day than previously thought. This sensitivity is used to estimate the comfort temperatures and to establish a curve relating the probability of discomfort to the temperature-difference from the current optimum. Using the standard sensitivity, a reliable estimate of comfort temperature can be made from a small batch of data, and from batches whose summary statistics alone are known. This extends the quantity of available data from which to form the relation between indoor comfort and the climate. We draw on an extensive database of such summary statistics. Using this information the graphs relating the temperature for comfort indoors and the climate are updated. Bands are given within which the comfort temperatures are likely to lie, both for the free-running mode of operation and for the heated-or-cooled mode. The underlying mechanism of the relation between climate and indoor comfort is discussed. The data show that it is possible to design buildings to operate in the free-running mode so as to be comfortable when the prevailing mean outdoor temperature lies within the range 10–30 °C.

► An extensive database of summary statistics confirms general pattern of relation.
► Best metric for outdoor temperature an exponential running mean with alpha 0.8/day.
► People more sensitive to within-day temperature changes than thought (0.5votes/K).
► Graph of comfort temperature versus outdoor temperature is steeper (0.53/K).
► Free-running mode possible if mean outdoor temperature between 10 and 30 °C.