Thermal comfort in forested urban canyons of low building density. An assessment for the city of Mendoza, Argentina Erica Correa a, * , María Angélica Ruiz a , Alicia Canton a , Graciela Lesino b a INCIHUSA e LAHV, Instituto Ciencias Humanas Sociales y Ambientales (Institute of Environmental and Social Sciences), Laboratorio de Ambiente Humano y Vivienda (Human Environment and Housing Laboratory), (CONICET e CCT-Mendoza), CC. 131 5500 Mendoza, Argentina b INENCO - Instituto de Investigaciones en Energías No Convencionales (Non-Conventional Energy Research Institute) e U.N.Sa. e CONICET, Universidad Nacional de Salta (National University of Salta), Argentina article info Article history: Received 2 February 2012 Received in revised form 23 May 2012 Accepted 9 June 2012 Keywords: Bioclimatic urban design Arid regions Urban forestry Road channels COMFA method abstract This research has established the degree of comfort achieved in road channels of Mendoza Metropolitan Area (AMM), in Argentina. They present different widths (16 m, 20 m and 30 m) with low building density and they are forested with First (Platanus acerifolia) and Second (Morus alba and Fraxinus excelsior) Magnitude species. The methodology is based on the selection of cases, the experimental observation and the assessment of thermal comfort condition by applying the COMFA method. The energy budget evaluation shows that the road channels forested with Platanus acerifolia -whose green structure is characterized for continuous tunnel over street and sidewalk-, has the best behavior. Nevertheless taking into account the urban problems of the city under study, it is necessary to settle the comfort conditions with the possibility of nocturnal cooling. During the daytime the solar radiation control is a key to getting comfort conditions. During the nighttime, sky vision is needed for radiative cooling. In addition, the forest structure combined with the urban morphology increase soil roughness and reduces the convective cooling. Therefore it is necessary to encourage those combinations of forest structure and urban morphologies that benefit both processes in order to reduce the urban heat island. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The assessment of energy balance is fundamental in order to understand how an urban design can modify the energy flows [1]. Moreover, the characterization of urban radiant fields and the thermal behavior resulting from their interactions with the urban morphology, the green structure and the local climate features is a basic tool to assess both energy consumption and the environ- mental pollution associated with urbanization. At the same time, data of the distribution of arid regions shows that many important cities are in dry lands. Also, approximately one third of the world population lives in extremely arid, arid or semi-arid regions and therefore cities located in these areas display a compact urban model characterized by narrow streets and buildings with inter- laced small-sized backyards [2]. Created shades reduce the sun exposure in warmer seasons and, consequently, the heat accumu- lation on heavy material surfaces e surfaces with high thermal admittance. The Mendoza Metropolitan Area (MMA) is located in central western Argentina, (32  40 0 southern latitude, 68  51 0 western longitude, 750 m above sea level) in a semi-arid continental climate with low percentages of atmospheric relative humidity and high heliophany. It corresponds to the aridity index of 0.20e0.50 (aridity index ¼ precipitation/potential evapotranspiration) according to Maps of Desertification Hazard of Central Western Argentina [3] see Fig. 1 . Although, MMA is located in a semi-arid region, it does not follow the aforementioned compact urban model. Their urban model is defined by its wide and tree-lined streets that form green tunnels. The checkered frame contains the buildings while the main strategy for minimizing the sun exposure is the vegetal frame. For this reason, the present study takes into account the impact on thermal comfort of the urban forestry along side the streets in MMA. Moreover, the study makes a contribution to a more general scholarly discussion. In recent years, the concept of sustainable development has stressed the fact that some urban forms significantly reduce energy consumption and pollution. For example, the “green urbanism” is broadly considered a better design for a more sustainable city [4]. In the last thirty years, we have seen an increasing scientific knowledge as well as a more general awareness about the beneficial effects of green areas and vegetal biomass [5e15]. * Corresponding author. Tel.: þ54 261 45244054; fax: þ54 261 5244001. E-mail address: ecorrea@mendoza-conicet.gov.ar (E. Correa). Contents lists available at SciVerse ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv 0360-1323/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.buildenv.2012.06.007 Building and Environment 58 (2012) 219e230