A simple technique to classify urban locations with respect to human thermal comfort: Proposing the HXG scale

An attempt is made to present a new scale to study urban microclimates and outdoor thermal comfort using simple in-situ measurement data. For this purpose, six urban locations with distinct physical characteristics are selected in a metropolitan city, Chennai. At each location, three streets with diverse orientations (North-south; East-west and Northeast-southwest) are identified and their microclimatic conditions are monitored during the summer months of April, May and June. The variations in microclimate are studied using ANOVA single factor test and later, correlated with the site's physical characteristics. The assessment of microclimate and outdoor thermal comfort is done using Physiological equivalent temperature (PET). The results show that the site physical factors like the H/W ratio and green cover index show poor and moderate correlations respectively (R-2 of 0.016 and 0.445) when regressed with the mean PET. In this regard the proposed HXG (read as H cross G) scale displays satisfactory correlation (R-2 = 0.648). The HXG scale constitutes a product between the height to width (H/W) ratio and green cover percentage of a location and provides a fair idea about the locality's microclimatic conditions. This method to study and classify urban microclimates may prove useful in the context of urban design and planning. (C) 2011 Elsevier Ltd. All rights reserved.