Page 26 - GRIHA Manual Volume III - Introduction to National Rating System
P. 26
Building and system design optimization 19
Example
Assume the following climatic conditions.
The outdoor solar incident energy (on a 1m x 1m glass area) = 800 W/m 2
Temperature differential between inside and outside = 20 ºC
SHGC of selected glass = 0.3
U-factor of selected glass = 3.0
The heat gain inside the building through SHGC of glass = 800 × 0.3 = 240 W
The heat gain inside the building through SHGC of glass = 20 × 3.0 = 60 W
Therefore, the total heat gain inside the building = 300 W
Heat gain due to SHGC = 80% of the total heat gain
7. Adequate daylighting
Daylight is a natural source of light, which meets all the requirements of good lighting while
enhancing user efficiency and productivity. In India, daylight is available in plenty under clear
sky conditions, and can be used for satisfactory indoor illumination during the day. By proper
design of windows in terms of their orientation, size, and shape, one can eliminate the use of
artificial lighting in most buildings during daytime. Building spaces with poor daylight availability
and spaces with nighttime usage can be provided with supplementary artificial lighting, as
per requirement. Direct sunlight is excluded from the definition of daylight factor, as it is not
desirable from the viewpoint of lighting quality. It creates problems of harsh shadows, and severe
brightness imbalances resulting in glare. Direct sunlight also results in undesirable heat in summer.
Therefore, adequate shading devices are recommended not only for thermal comfort but also for
visual comfort.
Daylight penetration inside the living space depends entirely on the building design, that is, the
orientation, internal space arrangement, distribution of openings, size and shape of the openings,
shading design and glazing properties, and so on. An optimum building design allows for maximum
penetration of daylight available in the building’s surroundings. Therefore, GRIHA mandates the
daylight clause and even encourages increasing the daylighted area inside the building by awarding
additional points for the same. Sometimes, given the diverse site constraints, building designers may
face certain limitations with respect to sufficient daylight integration in the buildings. Therefore, a
minimum requirement for the provision of daylight in building design has been made mandatory.
The daylight clause of Criterion 13 has been framed around various standards and benchmarks to
limit all the parameters of daylight design. The major daylight design parameters (as per GRIHA) are
as follows.
a. Defined daylighted area/daylight zone
b. Defined living area
c. Recommended daylight factor (DF)
d. Fixed design sky condition
a. Daylighted area
The daylighted area is the daylight illuminated floor area under horizontal fenestration (skylight) or
adjacent to vertical fenestration (window), as described in Appendix A of ECBC-2007.
Example
Assume the following climatic conditions.
The outdoor solar incident energy (on a 1m x 1m glass area) = 800 W/m 2
Temperature differential between inside and outside = 20 ºC
SHGC of selected glass = 0.3
U-factor of selected glass = 3.0
The heat gain inside the building through SHGC of glass = 800 × 0.3 = 240 W
The heat gain inside the building through SHGC of glass = 20 × 3.0 = 60 W
Therefore, the total heat gain inside the building = 300 W
Heat gain due to SHGC = 80% of the total heat gain
7. Adequate daylighting
Daylight is a natural source of light, which meets all the requirements of good lighting while
enhancing user efficiency and productivity. In India, daylight is available in plenty under clear
sky conditions, and can be used for satisfactory indoor illumination during the day. By proper
design of windows in terms of their orientation, size, and shape, one can eliminate the use of
artificial lighting in most buildings during daytime. Building spaces with poor daylight availability
and spaces with nighttime usage can be provided with supplementary artificial lighting, as
per requirement. Direct sunlight is excluded from the definition of daylight factor, as it is not
desirable from the viewpoint of lighting quality. It creates problems of harsh shadows, and severe
brightness imbalances resulting in glare. Direct sunlight also results in undesirable heat in summer.
Therefore, adequate shading devices are recommended not only for thermal comfort but also for
visual comfort.
Daylight penetration inside the living space depends entirely on the building design, that is, the
orientation, internal space arrangement, distribution of openings, size and shape of the openings,
shading design and glazing properties, and so on. An optimum building design allows for maximum
penetration of daylight available in the building’s surroundings. Therefore, GRIHA mandates the
daylight clause and even encourages increasing the daylighted area inside the building by awarding
additional points for the same. Sometimes, given the diverse site constraints, building designers may
face certain limitations with respect to sufficient daylight integration in the buildings. Therefore, a
minimum requirement for the provision of daylight in building design has been made mandatory.
The daylight clause of Criterion 13 has been framed around various standards and benchmarks to
limit all the parameters of daylight design. The major daylight design parameters (as per GRIHA) are
as follows.
a. Defined daylighted area/daylight zone
b. Defined living area
c. Recommended daylight factor (DF)
d. Fixed design sky condition
a. Daylighted area
The daylighted area is the daylight illuminated floor area under horizontal fenestration (skylight) or
adjacent to vertical fenestration (window), as described in Appendix A of ECBC-2007.
