Page 66 - GRIHA Manual Volume II - Introduction to National Rating System
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58 GrIha Manual: Volume 2
Table 5.2 National Building Code 2005 standards for imperviousness factor applicable to different types of area
Type of area Imperviousness factor (%)
Commercial and industrial areas 70–90
Residential areas (high density) 60–75
Residential areas (low density) 35–60
Parks and underdeveloped areas 10–20
5.2 Compliance
The following may be submitted.
5.2.1 Calculations to support design commitment, as per following equations (1–4).
Net impervious area on ground (m )
2
Net Paved area (%) = x 100 Equation (1)
Total site area minus building footprint (m )
2
Impervious paved area on-site to include parking, driveways, sidewalks, roads, boundary wall,
and often, plazas and walkways. Exclude areas that have pervious paving (like grass pavers, open
grid pavements, and gravel paving). Total site area is an area of plot used for calculation of floor
area ratio/floor space index.
2
Net imperviousness of site (m ) = Surface area x Runoff coefficient
(from Table 5.1) Equation (2)
2
Net imperviousness of site as per Equation 2 (m )
Imperviousness (%) = x 100 Equation (3)
2
Total site area (m )
(Pervious paving+paving with vegetated roof/shading+paving with high SRI ) > 50%
Equation (4)
Total paved area
Total paved area on-site to include parking, driveways, sidewalks, roads, boundary wall, and often
plazas and walkways.
5.2.2 Site plan (one drawing) with area statements clearly showing all paved areas (paved areas
should be labelled as per use, for example, walkways, driveways, parking, sit outs, and so
on). The following details should be followed as applicable.
# Demarcate areas that have vegetated roof. Provide details of vegetated roof.
# In case high reflectance surface is provided, submit details of reflectance of surface
finish.
# Demarcate areas having previous paving.
5.2.3 Certificate by architect to certify that total surface parking not to exceed as permitted by
local bye-law.
Table 5.2 National Building Code 2005 standards for imperviousness factor applicable to different types of area
Type of area Imperviousness factor (%)
Commercial and industrial areas 70–90
Residential areas (high density) 60–75
Residential areas (low density) 35–60
Parks and underdeveloped areas 10–20
5.2 Compliance
The following may be submitted.
5.2.1 Calculations to support design commitment, as per following equations (1–4).
Net impervious area on ground (m )
2
Net Paved area (%) = x 100 Equation (1)
Total site area minus building footprint (m )
2
Impervious paved area on-site to include parking, driveways, sidewalks, roads, boundary wall,
and often, plazas and walkways. Exclude areas that have pervious paving (like grass pavers, open
grid pavements, and gravel paving). Total site area is an area of plot used for calculation of floor
area ratio/floor space index.
2
Net imperviousness of site (m ) = Surface area x Runoff coefficient
(from Table 5.1) Equation (2)
2
Net imperviousness of site as per Equation 2 (m )
Imperviousness (%) = x 100 Equation (3)
2
Total site area (m )
(Pervious paving+paving with vegetated roof/shading+paving with high SRI ) > 50%
Equation (4)
Total paved area
Total paved area on-site to include parking, driveways, sidewalks, roads, boundary wall, and often
plazas and walkways.
5.2.2 Site plan (one drawing) with area statements clearly showing all paved areas (paved areas
should be labelled as per use, for example, walkways, driveways, parking, sit outs, and so
on). The following details should be followed as applicable.
# Demarcate areas that have vegetated roof. Provide details of vegetated roof.
# In case high reflectance surface is provided, submit details of reflectance of surface
finish.
# Demarcate areas having previous paving.
5.2.3 Certificate by architect to certify that total surface parking not to exceed as permitted by
local bye-law.
