Page 69 - GRIHA Manual Volume II - Introduction to National Rating System

Sustainable site planning 61

Figure 4 Shaded hard surface and shaded parking

The following are the respective areas of each.
Table 1 Site area break-up
Surface Area (in m )
2
Road 1052
Sidewalk 148
Impervious area in landscape pathway 616-216= 400
Café court 78
Emergency access paving 947
Surface parking 75
Net paved area 2700

Site area to be considered in equation1 is site area minus the building footprint. Thus the site area is
2
12 500 – 500 = 12 000 m .
Thus, according to Equation 1.

Net paved area % = [Impervious area on ground/(total site area – building footprint)] x100
= (2700/12 000) x100 = 22.5%

Now, calculating the impervious area according to Equation 2.

Table 2 Imperviousness of various surfaces on site
Surface Area (in m ) Run-off coeficient Impervious area (in m )
2
2
Roof garden (175mm thick) 125 0.3 37.5
Conventional roof 375 0.95 356.25
Concrete paving 2768 0.95 2629.6
Brick paving 148 0.85 125.8
Vegetation (turf slope 0–1) 9048 0.25 2262
Net imperviousness of site 5411.15

Equation 3
Imperviousness paving % = net imperviousness area of site from Equation 2/total site area
(imperviousness factor)