Predicting urban outdoor thermal comfort by the Universal Thermal Climate Index UTCI—a case study in Southern Brazil

Abstract

Recognising that modifications to the physical attributes of urban space are able to promote improved thermal outdoor conditions and thus positively influence the use of open spaces, a survey to define optimal thermal comfort ranges for passers-by in pedestrian streets was conducted in Curitiba, Brazil. We applied general additive models to study the impact of temperature, humidity, and wind, as well as long-wave and short-wave radiant heat fluxes as summarised by the recently developed Universal Thermal Climate Index (UTCI) on the choice of clothing insulation by fitting LOESS smoothers to observations from 944 males and 710 females aged from 13 to 91 years. We further analysed votes of thermal sensation compared to predictions of UTCI. The results showed that females chose less insulating clothing in warm conditions compared to males and that observed values of clothing insulation depended on temperature, but also on season and potentially on solar radiation. The overall pattern of clothing choice was well reflected by UTCI, which also provided for good predictions of thermal sensation votes depending on the meteorological conditions. Analysing subgroups indicated that the goodness-of-fit of the UTCI was independent of gender and age, and with only limited influence of season and body composition as assessed by body mass index. This suggests that UTCI can serve as a suitable planning tool for urban thermal comfort in sub-tropical regions.

UTCI-Fiala multi-node model of human heat transfer and temperature regulation

“…These are characterised by non-moderate ambient temperatures, elevated wind speeds, and solar radiation conditions. A description of the COST 730 validation and inter-model comparison exercise is provided by Psikuta et al (2011), Bröde et al (2011b, and Kampmann et al (2010) in this special issue. the original 19-compartment, 342-node model is configured as a symmetric 12-compartment, 187-node model whose left and right extremities and spatial body sectors are merged to lumped entities.…”

The UTCI-clothing model

“…The most important feature of this clothing behaviour is that people do not adjust their clothing to the climate requirements completely and seem to 'under-dress' in the cold. The approach followed here requires further validation, though first results presented in this issue indicate that it may also be applicable to a urban areas in other continents (Bröde et al 2011). The principles derived in this action allow the extension to e.g.…”

The urban microclimate in open space. Case studies in Madrid

“…In order to evaluate the thermal comfort, the Universal Thermal Climate Index (UTCI) (Jendritzky et al 2012, Bröde et al 2012b, Bröde et al 2012a, Fiala et al 2012) has been used. The UTCI is developed by the research activities compiled by COST Action 730, with the main objective of developing one internationally recognized model.…”

“…The index allows the calculation of comfort conditions using climate values obtained from in situ measurements or analytical calculation. The UTCI 7 follows the Equivalent Temperature (ET) concept, which involves an environment reference at 50% relative humidity (vapour pressure is capped at 20 hPa), in addition, air and radiant temperature equal air temperature (Bröde et al 2012b). The physiological response has been calculated for a single person, considering clothing insulation after 30 and 120 min of exposition.…”

“…The selection of the index has influenced the choice of the calculation system too, because it should be able to provide the output required for the index calculation. A review of the state of the art on outdoor thermal comforts indexes was done, and after conducting an empirical study of different systems; the Universal Thermal Climate Index (UTCI) (Jendritzky et al 2012, Bröde et al 2012b, Bröde et al 2012a, Fiala et al 2012) was chosen for this study.…”