Page 29 - GRIHA Manual Volume III - Introduction to National Rating System
P. 29
22 GRIHA Manual: Volume 3
The recommended DF in the daylight clause refers to the table 2 of SP41. The table represents the
daylight requirement for various types of living areas in terms of multiples of one daylight factor.
Therefore, as per this clause, the specified DF should be achieved at the centre of the daylighted
area (or as an average of the daylighted area).
Convert the daylight factor (DF) in to daylight level (lux)by multiplying it with the outside illuminance
level.
1 DF = 1% of outdoor illuminance
Example: Calculate the daylight level for kitchen space in warm-humid climatic zone
Outdoor illuminance = 9000 lux
1 DF at warm-humid = 90 lux
Minimum recommended DF for kitchen = 2.5
Minimum required daylight level in kitchen = 2.5 × 90 = 225 lux
d. Design sky condition
The basis of daylighting design adopted for the Indian standards is the clear design sky, which is
representative of the prevalent sky condition in India and ensures adequate daylight for most of
the working hours. The clear design sky basis holds good for any building orientation, and ensures
adequate daylight indoors for about 90% of the daytime working hours. In between the morning
and evening solar altitude of 15º, the indoor illumination increases as the sun goes up in the sky and
as it approaches the window.
The outdoor design sky illuminance varies for different climatic regions of the country. The
recommended design sky illuminance for different climatic zones is as follows.
1. Cold climate – 6800 lux
2. Composite climate – 8000 lux
3. Warm-humid – 9000 lux
4. Temperate – 9000 lux
5. Hot-dry – 10500 lux
The conversion of DF into daylight level is based on outdoor luminance or design sky condition for
the lighting analysis. Hence, for integration with artificial lighting during daytime working hours,
an increase of 500 lux in the recommended sky design illuminance for daylighting is suggested by
National Building Code (NBC)-2005.
Daylight simulation
Various softwares such as, ECOTECT, RADIANCE, IES, AGI-32, Lumen Designer, DIALUX, and so on are
used for daylight analysis and to measure the available daylight factor on the working plane with
specific design sky conditions and specific window properties. To perform the daylight simulation,
certain parameters need to be finalized and set in the simulation tool, such as, the dimension and
location of the proposed window, depth and pattern of shading devices and glazing specifications
(Visible Light Transmission), internal reflectance of floor, wall, and ceiling, outdoor luminance/sky
conditions, external and internal obstructions, and so on.
The recommended DF in the daylight clause refers to the table 2 of SP41. The table represents the
daylight requirement for various types of living areas in terms of multiples of one daylight factor.
Therefore, as per this clause, the specified DF should be achieved at the centre of the daylighted
area (or as an average of the daylighted area).
Convert the daylight factor (DF) in to daylight level (lux)by multiplying it with the outside illuminance
level.
1 DF = 1% of outdoor illuminance
Example: Calculate the daylight level for kitchen space in warm-humid climatic zone
Outdoor illuminance = 9000 lux
1 DF at warm-humid = 90 lux
Minimum recommended DF for kitchen = 2.5
Minimum required daylight level in kitchen = 2.5 × 90 = 225 lux
d. Design sky condition
The basis of daylighting design adopted for the Indian standards is the clear design sky, which is
representative of the prevalent sky condition in India and ensures adequate daylight for most of
the working hours. The clear design sky basis holds good for any building orientation, and ensures
adequate daylight indoors for about 90% of the daytime working hours. In between the morning
and evening solar altitude of 15º, the indoor illumination increases as the sun goes up in the sky and
as it approaches the window.
The outdoor design sky illuminance varies for different climatic regions of the country. The
recommended design sky illuminance for different climatic zones is as follows.
1. Cold climate – 6800 lux
2. Composite climate – 8000 lux
3. Warm-humid – 9000 lux
4. Temperate – 9000 lux
5. Hot-dry – 10500 lux
The conversion of DF into daylight level is based on outdoor luminance or design sky condition for
the lighting analysis. Hence, for integration with artificial lighting during daytime working hours,
an increase of 500 lux in the recommended sky design illuminance for daylighting is suggested by
National Building Code (NBC)-2005.
Daylight simulation
Various softwares such as, ECOTECT, RADIANCE, IES, AGI-32, Lumen Designer, DIALUX, and so on are
used for daylight analysis and to measure the available daylight factor on the working plane with
specific design sky conditions and specific window properties. To perform the daylight simulation,
certain parameters need to be finalized and set in the simulation tool, such as, the dimension and
location of the proposed window, depth and pattern of shading devices and glazing specifications
(Visible Light Transmission), internal reflectance of floor, wall, and ceiling, outdoor luminance/sky
conditions, external and internal obstructions, and so on.
