The urban heat island (UHI) effect, which has been increasing global temperatures, has a considerable influence on metropolitan areas. UHI refers to urbanised areas with significantly higher temperatures than their rural equivalents. Urban regions may be significantly warmer than rural areas despite their closeness for a variety of reasons related to urban growth and human activity. This temperature increase is produced by several variables that influence the local microclimate.
Urban regions comprise more than thirty percent of cities, thus there are several opportunities to reduce the effect of UHIs and increase urban resilience. Associated with rising global temperatures, the UHI effect has a significant impact on urban areas. Densely populated regions with significantly higher temperatures than those seen in rural areas are referred to as UHI areas. The UHI effect, which intensifies the effects of global warming in locations with high population density, has become more significant and urgent as global urbanisation and climate change continue to increase. As air pollution, energy usage, and heat discomfort rise, this has a significant effect on the lives of millions of people. As the consequences of UHIs intensify and become more obvious, proper urban planning and design are critical to addressing this growing problem
Strategies for Urban Heat Island Mitigation
Urban Forestry: The loss of vegetation, which affects evapotranspiration and the release of latent heat, plays an important role in the UHI effect. This effect can be mitigated by preserving existing biomass and planting more trees. Urban forestry limits the amount of sunlight reaching the ground, creates shade, and increases evapotranspiration. According to research, communities without greenery might be up to 5°C (9°F) hotter than those with vegetation.
Green Buildings: To produce long-lasting, sustainable structures, green buildings make use of rules, regulations, standards, and building materials. To lessen the UHI effect, green building techniques may be used in the planning, construction, operating, and maintenance phases. To offer more insulation and cooling, this involves implementing green walls, roofs, and urban greening techniques.
Including Urban Greening Practices: Urban greening techniques provide extra insulation and cooling through evapotranspiration. Building energy consumption may be decreased by around 0.7% and citywide temperatures can be lowered by about 2.8°C with green roofs and more trees surrounding buildings. In parking lots, combining the advantages of vegetation and permeability with materials like concrete, Grasscrete, or porous plastic pavement units can help cool the environment without sacrificing usability.
Permeable Surfaces: Permeable paving systems perform localised cooling better than impermeable surfaces, particularly when wet. Regular rainfall is necessary to maximise their cooling effect.
Urban Trees: Trees help mitigate the UHI effect by reflecting light and transpiring water, cooling the air. Large trees can transpire significant amounts of water annually, providing substantial cooling benefits. Street trees shade buildings and sidewalks, reducing the radiation that reaches lower albedo surfaces.
Incorporating Water into the Landscape: Water features, such as lakes, ponds, and daylighted streams, cool their surroundings through evaporation. Increasing the surface area of water features maximises this cooling effect.
Rainwater Harvesting: By collecting rainfall and letting it evaporate off surfaces, permeable pavements can produce more sustained cooling by balancing out peak stormwater flows.
Rain Gardens and Swales: Long-term evaporation and cooling are made possible by Sustainable Urban Drainage Systems (SUDS), which include rain gardens and swales. These features gather and gradually absorb runoff.
Reflective Surfaces: Using lighter-coloured materials or special reflective paints on roofs and other surfaces can decrease the amount of solar energy absorbed, reducing urban temperatures. Reflective paints that reflect invisible light while absorbing visible light are a potential solution to avoid glare.
Solar Panels: Photovoltaic panels can generate electricity while shading buildings, preventing heat absorption and reducing nighttime heat radiation.
Materials with Low Thermal Mass: Reducing the use of high thermal mass materials like concrete and opting for highly reflective materials such as glass or metals can minimise heat retention and lower urban temperatures.
Effective Urban Geometry: Wider streets with vegetation support better air circulation and prevent adjacent buildings from blocking airflow, reducing localised heating.
Vernacular Building Construction: Utilising readily available, environmentally friendly materials along with unique construction methods can improve the area’s attractiveness while simultaneously minimising the consequences of urban heat islands.
Copenhagen
Copenhagen has used innovative building techniques to reduce urban heat. The city’s
The surface hit 47°C on the warmest day of 2010, but temperatures outside the city were 12°C lower. Copenhagen has implemented a comprehensive adaptation strategy to address problems caused by climate change, including rising sea levels, more frequent rainstorms, and extreme heat in urban areas. The city has cut its CO2 emissions by around 20% in the last ten years, and 30% of its energy currently comes from carbon-neutral sources. In an attempt to lessen urban heat islands and stormwater runoff, the city has increased the usage of green space, including “pocket” parks, green walls, and green roofs. Green roofs collect sixty percent of precipitation, improving air quality and establishing animal habitats. To improve energy efficiency, Copenhagen is also upgrading historic structures with solar panels, green roof gardens, insulated doors, walls, and roofs. With this strategy, the effect of urban heat islands is lessened in addition to the surface temperatures being lowered. The green infrastructure of the city reduces strain on the sewage system, cools the city during heat waves, and manages rainwater.
Singapore: A Garden City
Singapore‘s commitment to incorporating nature into urban development to counteract the Urban Heat Island (UHI) effect is demonstrated by its designation as a “Garden City.” The city-state has created vast green spaces, parks, vertical gardens, and green buildings, all of which skilfully combine urban planning with the conservation of biodiversity. This system of green areas improves the quality of life for city dwellers and the urban microclimate while also naturally cooling the city. Singapore is a prime example of how innovative and comprehensive design can address urban heat in tropical cities by emphasising green space and sustainable development.
References:
Architects, J. (2018) How landscape architecture mitigates the urban heat island effect, Land8. Available at: https://land8.com/how-landscape-architecture-mitigates-the-urban-heat-island-effect/ (Accessed: 28 July 2024).
Bangad, Ar.M. and Vaijwade, U. (2022) Architecture as a Catalyst in Mitigating Heat Island Effect , sd conference. Available at: https://www.sdconference.org/uploads/1/1/4/7/11479227/architecture_as_a_catalyst_in_mitigating_heat_island_effect.pdf (Accessed: 28 July 2024).
Green, J. (2021) Urban heat islands are increasingly dangerous, but planners and designers have solutions, ArchDaily. Available at: https://www.archdaily.com/962913/urban-heat-islands-are-increasingly-dangerous-but-planners-and-designers-have-solutions (Accessed: 28 July 2024).
Salmanian, M. and Bayat, A. (2023) Urban heat island: a primary guide for urban designers, fupubco. Available at: https://fupubco.com/fuen/article/view/72/62 (Accessed: 30 July 2024).
Urban Design Lab (2024) What is an urban heat island?, Urban Design lab. Available at: https://urbandesignlab.in/what-is-an-urban-heat-island/ (Accessed: 29 July 2024).
Wells, D. (2023) Can strategic design & planning help combat the UHI effect?, Street Furniture Manufacturers & Suppliers UK | Landmark Street Furniture. Available at: https://landmarkstreetfurniture.com/can-strategic-design-planning-help-combat-the-uhi-effect/ (Accessed: 29 July 2024).
