Page 62 - GRIHA Manual Volume II - Introduction to National Rating System
P. 62
54 GrIha Manual: Volume 2
As the ambient temperature in urban centres rises due to UHIE, there is an increase in the use of
air conditioning to maintain comfortable ambient conditions inside te buildings. Air conditioning
radiates more heat back into the already warmer urban environment. This further adds to the UHIE,
and as a result, even more air conditioning is required. Thus, this forms a vicious circle, where the
cause and effect constantly affect each other. This leads to increased consumption of electricity and
hence, increased air pollution (as a consequence of electricity generation from fossil fuels).
The smoke from anthropogenic sources such as transportation and electricity generation
concentrates over urban centres and leads to formation of inversion layers. Formation of inversion
layers leads to increased absorption of radiation in the environment, further adding to the heat
island effect and simultaneously slows down the dispersion of air pollutants, leading to their
concentration over urban centres. Due to the creation of inversion layers, polluted air is trapped
inside the dome and recirculates within it, mixing with cleaner air and causing air pollution over the
entire city. Increased air pollution and heat also leads to the formation of smog. This leads to various
health problems.
As the perviousness of the surfaces decrease, the amount of water getting absorbed is reduced.
As a result, during monsoon, there is excessive water run-off in the city, which leads to flooding of
the streets and roads, and exerts great pressure on the city’s stormwater drains. Since all the water
gets drained off and is not absorbed, less energy is used from the environment for evaporation.
At a macro scale, since majority of emissions occur due to anthropogenic activities in the urban
region (electricity generation and consumption, emissions due to transportation etc.), UHIE contributes
significantly to global warming and climate change. It leads to modifications in the local weather
patterns, disrupting the regular rainfall patterns in the area, and increasing the incidence of heatwaves.
Solutions
In the same manner that one can segregate the causes of UHIE into macro and micro causes, the
solutions for the same can also be divided into macro- and micro-level initiatives. Since the scope of
this manual restricts itself to individual buildings, the solutions listed here are interventions that can
be taken at the scale of individual buildings.
1. Minimization of paved surfaces: Minimizing the paved area on site reduces UHIE. By reducing
the paved area, majority of the landscape area on site remains under softscape surfaces and
vegetation. By minimizing the paved area on site, the impact due to modification of site surface
is minimized.
2. Cool roofs: Buildings absorb a lot of heat from the roofs. Dark-coloured roofs also contribute to
UHIE. Dark surfaces can be up to 7° C hotter than the ambient air temperatures, whereas the
temperature of light coloured surfaces increases by just about 2°–3° C in similar conditions.
12
Albedo refers to the surface reflectivity of various materials. The higher the albedo, the more the
surface/material reflects the radiations falling on it. Thus in order to mitigate impacts of UHIE,
buildings should have light coloured roofs or should be coated with high albedo paints. Roofs
can even be covered with ceramic tiles which have high reflectance. Albedo is measured on a
scale of 0–1. The albedo of a dark surface ranges between 0.1 and 0.3, that of white-coloured
surfaces ranges between 0.5 and 0.6, and of high reflective paints is between 0.6 and 0.7. Roof
finishes like broken china mosaic tiles have high albedo and prevent heat gains.
12 Hien W N. 2002. A Study of the Urban Heat Island in Singapore, A Report of Heat Island Project, National University of Singapore.
As the ambient temperature in urban centres rises due to UHIE, there is an increase in the use of
air conditioning to maintain comfortable ambient conditions inside te buildings. Air conditioning
radiates more heat back into the already warmer urban environment. This further adds to the UHIE,
and as a result, even more air conditioning is required. Thus, this forms a vicious circle, where the
cause and effect constantly affect each other. This leads to increased consumption of electricity and
hence, increased air pollution (as a consequence of electricity generation from fossil fuels).
The smoke from anthropogenic sources such as transportation and electricity generation
concentrates over urban centres and leads to formation of inversion layers. Formation of inversion
layers leads to increased absorption of radiation in the environment, further adding to the heat
island effect and simultaneously slows down the dispersion of air pollutants, leading to their
concentration over urban centres. Due to the creation of inversion layers, polluted air is trapped
inside the dome and recirculates within it, mixing with cleaner air and causing air pollution over the
entire city. Increased air pollution and heat also leads to the formation of smog. This leads to various
health problems.
As the perviousness of the surfaces decrease, the amount of water getting absorbed is reduced.
As a result, during monsoon, there is excessive water run-off in the city, which leads to flooding of
the streets and roads, and exerts great pressure on the city’s stormwater drains. Since all the water
gets drained off and is not absorbed, less energy is used from the environment for evaporation.
At a macro scale, since majority of emissions occur due to anthropogenic activities in the urban
region (electricity generation and consumption, emissions due to transportation etc.), UHIE contributes
significantly to global warming and climate change. It leads to modifications in the local weather
patterns, disrupting the regular rainfall patterns in the area, and increasing the incidence of heatwaves.
Solutions
In the same manner that one can segregate the causes of UHIE into macro and micro causes, the
solutions for the same can also be divided into macro- and micro-level initiatives. Since the scope of
this manual restricts itself to individual buildings, the solutions listed here are interventions that can
be taken at the scale of individual buildings.
1. Minimization of paved surfaces: Minimizing the paved area on site reduces UHIE. By reducing
the paved area, majority of the landscape area on site remains under softscape surfaces and
vegetation. By minimizing the paved area on site, the impact due to modification of site surface
is minimized.
2. Cool roofs: Buildings absorb a lot of heat from the roofs. Dark-coloured roofs also contribute to
UHIE. Dark surfaces can be up to 7° C hotter than the ambient air temperatures, whereas the
temperature of light coloured surfaces increases by just about 2°–3° C in similar conditions.
12
Albedo refers to the surface reflectivity of various materials. The higher the albedo, the more the
surface/material reflects the radiations falling on it. Thus in order to mitigate impacts of UHIE,
buildings should have light coloured roofs or should be coated with high albedo paints. Roofs
can even be covered with ceramic tiles which have high reflectance. Albedo is measured on a
scale of 0–1. The albedo of a dark surface ranges between 0.1 and 0.3, that of white-coloured
surfaces ranges between 0.5 and 0.6, and of high reflective paints is between 0.6 and 0.7. Roof
finishes like broken china mosaic tiles have high albedo and prevent heat gains.
12 Hien W N. 2002. A Study of the Urban Heat Island in Singapore, A Report of Heat Island Project, National University of Singapore.
