D. Orientation and shading devices
Daylighting comes primarily from diffused daylight (from all directions) and much less from direct sunbeams.
In daylighting design, direct sunbeams should be blocked as much as possible because they carry much more heat and
create other problems such as glare and strong reflections.
Horizontal skylights have the biggest problem with direct sunbeams. A classic approach to skylight design is to have a
vertical skylight facing north. Otherwise, features such as deep mullions or shading devices should be employed to limit
the intrusion of direct sunbeams.
Shading devices should be designed according to their orientation for optimum results. Properly designed external and
internal shading devices have a similar effect in blocking direct sunbeams. External shading is less likely (as well as being
more expensive) to be adjustable as it is a permanent fixture and in place even when the sky is gloomy. Internal shading
devices are more easily adjustable and can respond to any outdoor conditions. However, if the shading device is heated
up, it will block the sunlight and emit the heat. External shading will emit the heat into the atmosphere without affecting
the interior. When the sun is strong, ultimately, a large part of the solar energy absorbed by the internal shading devices
will be emitted indoors and require the air conditioning system to counter it.
Figure 84 Example of design to block excessive direct sunlight and to
allow defused daylight from skylight facing north
Figure 85 Shopping spaces with diffused
daylight design, Citygate Outlets, Tung Chung
(Source: Swire Properties Limited)
4.3.2 Reflection and glare
Reflection of light by shop front windows prevents shoppers from seeing the shop’s interior and therefore should be
avoided in shopping malls. A shopping corridor with untempered daylight penetration can reach a luminance level up to
1000 lux during a very bright and sunny day even when no direct sunbeam problems exist. Shops become very dark
compared with the mall corridors. It is therefore essential to control daylight penetration, especially along corridors in front
of shops.
4
Green design for shopping malls and shop spaces
4.3
Natural lighting in shopping malls and shop spaces
110 Hong Kong Green Shop Guide
