Page 67 - GRIHA Manual Volume II - Introduction to National Rating System
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Sustainable site planning 59
5.3 Appraisal (maximum point 2)
5.3.1 Net paved area of site under parking, roads, paths, or any other use not to exceed 25%
of site area or net imperviousness of site should not exceed the imperviousness factor as
prescribed by National Building Code 2005, Part 9 (plumbing services) section 5.5.11.2.1,
whichever is more stringent. As per clause Equation 1 and Equation 3 (Reference
documents: 5.2.1. and 5.2.2.) (1 point)
5.3.2 Total surface parking not to exceed as permitted by local bye-laws (mandatory-if
applicable) and
# more than 50% of the total paved area to have pervious paving/open grid pavement/
grass pavers (equation 4), or
# minimum 50% of the total paved area (including parking) to have shading by vegetated
roof/pergola with planters (equation 4), or
# Minimum 50% of the total paved area (including parking) to be topped with finish
with solar reflectance of 0.5 or higher (equation 4) (Reference documents: 5.2.1. and
5.2.2.)
# a minimum 50% of the total paved area (including parking) to have any combination
of the above mentioned strategies, where common area having two or more strategies
shall be calculated only once. (equation 4) (1 point).
Methodology
The strategy to reduce UHIE and meet the criterion involves two steps (in the given order).
1 Reduce paved area on site; and
2 Reduce the thermal impacts of the hard-paved surfaces.
The steps are so arranged because the first step minimizes the total paved area on site. Once the
total paved area is minimized, the second step assists in further reducing its negative impact on
thermal comfort in the landscape areas and contribution towards UHIE.
Appraisal point 5.3.1 focuses on reducing the total paved area on site such that it does not
exceed 25% of the site area. This would ensure that the majority of the open surfaces on site are
either landscaped or soft paved. This reduces their contribution to UHIE. Simultaneously, this step
also ensures that most of the open surfaces have a low run-off coefficient which reduces the flow of
storm water into the city drains. Every surface has a different run-off coefficient. Run-off coefficient
of a surface indicates the rate of flow of water precipitating on top of the surface. Surfaces with
lower run-off coefficients reduce the rate of flow of water, thereby reducing flooding of the city
drains. By adopting more surfaces with lower run-off coefficients, the overall imperviousness factor
can be reduced.
Take the example of the following commercial complex.
2
2
The site is 125 m × 100 m. The site area is 12 500 m . The building footprint is 500 m . The paved
surfaces include the road, surface parking, walking trail in the landscape area, sidewalk along the
side of the road, open court in the café and emergency access provided around the building. The
2
total area under landscape pathway is 616m out of which 216m is softscaped.
2
5.3 Appraisal (maximum point 2)
5.3.1 Net paved area of site under parking, roads, paths, or any other use not to exceed 25%
of site area or net imperviousness of site should not exceed the imperviousness factor as
prescribed by National Building Code 2005, Part 9 (plumbing services) section 5.5.11.2.1,
whichever is more stringent. As per clause Equation 1 and Equation 3 (Reference
documents: 5.2.1. and 5.2.2.) (1 point)
5.3.2 Total surface parking not to exceed as permitted by local bye-laws (mandatory-if
applicable) and
# more than 50% of the total paved area to have pervious paving/open grid pavement/
grass pavers (equation 4), or
# minimum 50% of the total paved area (including parking) to have shading by vegetated
roof/pergola with planters (equation 4), or
# Minimum 50% of the total paved area (including parking) to be topped with finish
with solar reflectance of 0.5 or higher (equation 4) (Reference documents: 5.2.1. and
5.2.2.)
# a minimum 50% of the total paved area (including parking) to have any combination
of the above mentioned strategies, where common area having two or more strategies
shall be calculated only once. (equation 4) (1 point).
Methodology
The strategy to reduce UHIE and meet the criterion involves two steps (in the given order).
1 Reduce paved area on site; and
2 Reduce the thermal impacts of the hard-paved surfaces.
The steps are so arranged because the first step minimizes the total paved area on site. Once the
total paved area is minimized, the second step assists in further reducing its negative impact on
thermal comfort in the landscape areas and contribution towards UHIE.
Appraisal point 5.3.1 focuses on reducing the total paved area on site such that it does not
exceed 25% of the site area. This would ensure that the majority of the open surfaces on site are
either landscaped or soft paved. This reduces their contribution to UHIE. Simultaneously, this step
also ensures that most of the open surfaces have a low run-off coefficient which reduces the flow of
storm water into the city drains. Every surface has a different run-off coefficient. Run-off coefficient
of a surface indicates the rate of flow of water precipitating on top of the surface. Surfaces with
lower run-off coefficients reduce the rate of flow of water, thereby reducing flooding of the city
drains. By adopting more surfaces with lower run-off coefficients, the overall imperviousness factor
can be reduced.
Take the example of the following commercial complex.
2
2
The site is 125 m × 100 m. The site area is 12 500 m . The building footprint is 500 m . The paved
surfaces include the road, surface parking, walking trail in the landscape area, sidewalk along the
side of the road, open court in the café and emergency access provided around the building. The
2
total area under landscape pathway is 616m out of which 216m is softscaped.
2
