Climate Adaptability of Buildings by Mitja Košir

Author:Mitja Košir
Language: eng
Format: epub
ISBN: 9783030184568
Publisher: Springer International Publishing

4.2 Bioclimatic Charts

First attempts to define a relationship between climate parameters and human thermal comfort with the purpose of identifying when climate alone can provide comfortable conditions can be traced back to 1923 and the introduction of the Effective Temperature (ET) index by Houghton and Yaglou (Koenigsberger et al. 1975; Roshan et al. 2017). The ET correlated RH, temperature and air movement to human comfort. Later on, also the influence of solar radiation was included with the introduction of the corrected ET (cET) index. Both indexes were displayed as lines of achieved comfort on a psychrometric chart (from Latin “psuchron” for cold and “metron” meaning to measure), which is used to study the air and water vapour mixture’s thermodynamic properties. A simplified psychrometric chart is presented in Fig. 4.3 as a basis of Givoni’s bioclimatic chart. However, as previously mentioned, Olgyay was the first that attempted to devise the bioclimatic chart purposely designed for the use in the built environment (Olgyay 1963; La Roche 2017; Roshan et al. 2017). In his bioclimatic chart Olgyay related RH plotted on the abscissa with the dry bulb temperature (Tdb) plotted on the ordinate to define the comfort conditions of building occupants. In addition to the humidity and temperature, Olgyay’s bioclimatic chart also plots the lines with the impact of the solar irradiance in W/m2, air movement in m/s, mean radiant temperature (Tmr) of the building enclosure in °C and humidification in g/kg on the level of occupant’s comfort. The comfort zone in Olgyay’s chart is defined as an area between 21 and 27 °C and 20 and 80% of RH. This rectangular comfort zone is truncated and slightly shifted towards lower temperatures at RH above 50%, because humans evaluate thermal conditions as less comfortable at higher levels of humidity due to lowered potential for evaporative cooling of the body (see Chap. 2, Sect. 2.​1.​1). This defined comfort zone is often related to as the summer comfort zone as it outlines the comfort extent during the warmer half of the year. Therefore, Olgyay additionally demarcated the winter comfort zone, which is identical in shape to the summer comfort zone, however the temperature range is narrower (i.e. 20–24 °C) and shifted downwards by 1 °C. The extent of the winter and summer comfort zones in Olgyay’s bioclimatic chart was determined with the presumption of occupant’s metabolic rate (Mm) of 126 W, clothing insulation of 1 clo units (1 clo = 0.155 (m2K)/W—undergarment, socks, long trousers, long-sleeve shirt and sweater) and movement of the air between 0.45 and 0.90 m/s (Olgyay 1963; Košir and Pajek 2017; Pajek and Košir 2017). Olgyay’s bioclimatic chart is presented in Fig. 4.2.

The lower limit of the summer comfort zone corresponds to the shading line, which defines the combinations of Tdb and RH when blocking of the incident solar radiation is needed to achieve comfort. Specifically, when a combination of Tdb and RH is above this line and solar irradiance is present, shading is needed in order to achieve comfort. Correspondingly, the inverse

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