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Permeable pavements
Permeable materials (porous asphalt and concrete, interlocking concrete blocks, grass pavers) have high moisture content that can cool through evaporation also. Surface temperatures can be reduced by 20-33 °C with permeable surfaces.
Shading
External or internal, fixed, or dynamic, structures or devices to obstruct sun rays falling on surfaces and prevent heat gain through radiation. Shades can be fixed or dynamic i.e. movable depending on user preferences. Shading can reduce surface temperatures by up to 15 °C.
Green roofs
Dark-colored roofs and surfaces absorb and transfer greater heat, gained from solar radiation, inside buildings. Electricity consumption is increased in countering this heat. Cool roofs and walls reflect about 80% of the solar radiation falling on them and reduce the transfer of heat to interior spaces. Their surface finishes (paints, tiles, sheets, membranes) are of light- colored and highly reflective (albedo > .65) material. They can reduce indoor temperatures by 1-5 °C.
Vertical or horizontal greenery
Vegetation and trees on building facades (walls) and on theground adjacent to buildings cool through both shading and evapotranspiration. Temperatures of walls and surfaces covered with greenery can be up to 5-15 °C less compared to unshaded surfaces. Greenery can also reduce temperatures of adjacent indoor spaces by up to 2 °C.
Cool pavements
Dark-colored, impervious surfaces such as concrete and asphalt have low solar reflectance (about 40%) and increase local temperatures because they absorb and re-radiate heat, especially at night time. ‘Cool pavements’, made of light-colored materials (white paint, white asphalt), absorb less heat because of low heat conductivity, high reflectivity, and low heat storage capacity. Surface temperatures can be reduced by 20-33 °C with reflective surfaces. Increasing the reflectivity of impervious, dark-colored surfaces by 10% can reduce ambient temperatures by up to 0.9 °C.
Water-sensitive urban design
Stormwater harvesting and treatment systems centered on vegetation (shrubs, grasses, flowers, trees, etc.) contribute to cooling through evapotranspiration from plants and by reducing heat-absorbing, impervious surfaces. Raingardens, bioswales, and infiltration basins are primary examples that use plant roots and soil to clean polluted rainwater and discharge it to the ground. These can be added to road medians, sidewalks, car parks, roundabouts, etc.
Water-based cooling
Water-based cooling Water is a natural heat sink because of its excellent heat absorbing properties and removes heat from air through evaporation. Water bodies such as pools and fountains can be used inside buildings and in open spaces to lower temperatures with zero to minimal energy use. Surface or running water can reduce temperatures by at least 4-5 °C. Evaporative cooling systems can reduce ambient temperatures between 3 to 8 °C.
Public space shading
Free-standing structures (of metal concrete or wood), canvas sails, and tree canopies that protect from direct solar radiation on pedestrian pathways and activity zones in open spaces. These also reduce outdoor surface and near-surface temperatures thereby increasing thermal comfort. Shading devices can reduce temperatures by up to 15 °C.
Cool roofs and facades
Dark colored roofs and surfaces absorb and transfer greater heat, gained from solar radiation, inside buildings. Electricity consumption is increased in countering this heat. Cool roofs and walls reflect about 80% of the solar radiation falling on them and reduce transfer of heat to interior spaces. There surface finishes (paints, tiles, sheets, membranes) are of light-colored and highly reflective (albedo > .65) material. They can reduce indoor temperatures by 1-5 °C and roof surface temperatures by up to 33 °C.
Green cover: urban parks and street tree planting
Covering open spaces with grass or other vegetation and increasing tree canopy cover mitigates heat through both shading and evapotranspiration (release of water from plants into the atmosphere). Urban parks can decrease surface temperatures by up to 1 °C. A 10% increase in tree canopy cover can reduce the day-night temperature difference in summers by 1 °C. Ambient temperatures can be reduced by up to 4 °C by planting trees on streets.
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