An Investigation into Minimizing Urban Heat Island (UHI) Effects: A UK Perspective

Abstract

Cities are major sources of Green House Gas (GHG) emissions and the effects of mass urbanization upon the environment have now become clear. Great opportunities exist within cities for tackling climate change. Urban Heat Island (UHI) effect is a phenomenon where significant temperature difference between inner micro-climates of a city and their neighboring microclimates can be perceived. Mitigation of UHI effects can positively contribute to alleviate detriments of climate change. This research project aims to investigate effective and resilient UHI mitigation strategies and to provide guidance for their application in future. A review of literature indicates that UHI is a growing problem in the UK and that mitigation of such effects would enhance sustainable development at urban scale. The lack of guidance for designers and planners looking into mitigating the UHI effect is also identified. Utilizing ENVI-met simulations and through Urban Futures Assessment Method (UFAM), this research identifies and tests resilient and effective UHI mitigation strategies. Results show that building form, orientation and layout are among the most effective UHI mitigation strategies. Trees, shrubs and grass (TSG), and use of high albedo materials (HAM) in external building surfaces are also indicated as effective measures whose success is dependent on building form. All assessed mitigation strategies (TSG, HAM, UIWB) are shown to have a similar level of resilience which could be improved if properly future-proofed against subsequent changes. Accordingly some practical suggestions are provided to help improve the resilience of tested UHI mitigation strategies.

Vulnerabilidade às Ilhas de Calor no Município de São Paulo: Uma Abordagem para a Implantação de Medidas Mitigadoras na Gestão Urbana

“…Dentre os principais efeitos das ilhas de calor, destacam-se: (i) o aumento do número de mortes relacionadas ao aumento da temperatura e poluição (Dhalluin & Bozonnet, 2015;Kleerekoper, Van Esch & Salcedo , 2012;Mirzaei, 2015); (ii) o aumento do consumo de energia devido ao uso do ar condicionado (Dhalluin & Bozonnet, 2015;Mirzaei, 2015); (iii) a alteração da circulação de ar, favorecendo a convecção local e precipitação (O'Malley et al, 2014;Yan et al, 2016); (iv) a redução da velocidade do ar e dispersão de poluentes (Fernández et al, 2015;Santamouris et al, 2011); e (v) a alteração de temperatura pode influenciar negativamente na fauna e flora urbanas (Gartland, 2008).…”

“…Capítulo I Artigo 12; Artigo 25 (São Paulo, 2014) Implantação e conservação de espaços verdes, plantio de árvores e telhados verdes (Akbari & Kolokotsa, 2016;Gago et al, 2013;O'Malley et al, 2014) Preservação de corpos d'água (Kleerekoper et al, 2012) Design e forma urbana (Aflaki, Mirnezhad, Ghaffarianhoseini, Omrany, Wang & Akbari, 2016;Gago et al, 2013) Utilização de materiais com alta reflectância solar nas fachadas dos prédios, telhados e pavimentos (Aflaki et al, 2016;Akbari & Kolokotsa, 2016;Gago et al, 2013;O'Malley et al, 2014) Quadro 2 -Quadro síntese das estratégias propostas no PDE e as principais recomendações encontradas na literatura Este trabalho objetivou a busca por dados públicos acessíveis, bem como utilização de metodologia referenciada na prática internacional de desenvolvimento de índices. Dessa forma, apresenta-se replicável para outros contextos, guardadas às restrições de disponibilidade e qualidade dos dados.…”

“…A concentração de edifícios altos com materiais de alta retenção de calor, juntamente com calçadas e pavimentos impermeáveis, configuram canyons (Fernández, Alvarez-Vázquez, García-Chan, Martínez, & Vázquez-Méndez, 2015). Além disso, a alta concentração de poluentes e a emissão de calor antropogênico, também alteram os padrões locais circulação de ar (Fernández et al, 2015;O'Malley, Piroozfarb, Farr, & Gates, 2014;Santamouris, Synnefa, & Karlessi, 2011). Essas são potenciais causas das ilhas de calor urbano, fenômeno este que pode ser caracterizado pelo aumento da temperatura do ar no centro de áreas urbanas construídas, em comparação com as áreas circundantes rurais ou suburbanas, principalmente devido às atividades humanas (Yan, Wang, Xia & Feng, 2016).…”

The Impact of Morphological Features on Summer Temperature Variations on the Example of two Residential Neighborhoods in Ljubljana, Slovenia

“…According to Emmanuel and Loconsole [5], even when urban growth has subsided, the local warming that results from urban morphology (increased built cover, anthropogenic heat generation, pollution, lack of vegetation) generates local heat islands. O'Malley et al [6] demonstrate that building form, orientation, and layout are among the most effective UHI mitigation strategies. Harnessing natural wind patterns in designing the layout of buildings and presence of water in the form of urban water bodies, such as ponds, are also suggested to reduce temperature.…”

“…Vegetation makes the environment cooler through evaporation from the Earth's surface and transpiration of the vegetation [8]. The UHI effect is mitigated by grass, shrubs (e.g., hedges of a height of 1.5 m), and trees of 5-10 m in height with dense crowns [6]. Oke's model [11] approaches the heat island phenomenon both vertically and horizontally.…”