The use of sun control and shading devices is an important aspect of much energy-efficient building design.
Shading devices can have a dramatic impact on building appearance.
The energy a building requires can be divided into two basic categories.
First, the energy needed so that a building can be used, to create a comfortable climate.
This means the production and control of heat, cold, light and air.
Second, the additional energy required, dependant on the use of the building such as to power computers and secondary equipment in office and administrative buildings, or for production machines on the factory floor.
Appropriate sun shading systems can significantly reduce the energy required to provide heating, cooling and light.
Control intense direct sunlight will ensure a comfortable workspace.
This is critical for occupant visual and thermal comfort and for minimizing mechanical cooling loads.
In sunny weather, solar heat gains through glazing can represent a substantial input of heat to a building.
Apart from the direct solar heating, re-radiated heat becomes trapped inside the building, increasing the internal temperature even more.
Ventilation rates or cooling loads must then be increased to maintain comfortable conditions.
Sun shading is an effective complementary strategy to air conditioning or mechanical ventilation, providing savings in running costs as well as general energy savings and reduced CO2 emissions.
In naturally ventilated buildings it will provide lower internal temperatures by reducing the effects of solar heat gain.
A proper designed external shading can reduce solar heat gain from glazing by up to 85%.
External shading cuts out solar energy before it enters the building.
Shading against solar heat gain is the most readily applicable and flexible method of cooling and can be applied in all climate types.
The key to good day lighting and thermal performance lies in the design of the building envelope.
The traditional roles of shading systems are to improve thermal and visual comfort by reducing overheating and glare, and to provide privacy.
Shading systems perform a number of roles, the most apparent of which is protection from direct solar radiation and the resultant unwanted build up of heat inside the building.
Shading devices can be an integral part of the envelope, and thus influence thermal and day lighting performance.
By intercepting solar radiation before it reaches the building, external devices are the most effective at preventing the build up of solar heat gain inside.
Internal devices with a reflective external coating can reflect solar radiation to the outside, but transfer some of their solar heat gain to the room by convection.
This protection is best achieved by shading the building’s windows and other apertures.
Shading the building facades and roof can also significantly reduce unwanted heat build-up, particularly when these elements are un-insulated.
Apart from commercial buildings that experience high internal heat gains from office equipment and occupants, solar radiation represents the major influence on cooling loads in buildings.
Shading the building envelope and apertures directly reduces the need for cooling.
The direct component is more influential than the diffuse, and exerts its most immediate impact on cooling load when it reaches windows and other apertures because it is transmitted directly to the building interior.
Of the various types of shading system, external devices are the most effective in reducing heat gains because they intercept and disperse (largely by convection) most of the heat in solar radiation before it reaches the building surface.
However, they tend to be more expensive to install and maintain, and have a greater impact on the aesthetic character of the building.
Seasonal external shading can be provided by vegetation, typically deciduous and evergreen trees, vines, and shrubs.
Fixed external shading is generally in the form of horizontal overhangs, vertical fins and permanent awnings or shutters.
Moveable external shading refers to louver, blind, awning and shutter systems that can be adjusted to different climatic conditions, and can be fully retractable and automated.
They are very effective at controlling direct, diffuse and reflected light, and are thus able to modulate heat gains as well as daylight levels.
They can also provide unobstructed ventilation across the aperture and façade and, when retracted, cause no obstruction to light in overcast sky conditions.
Power-assisted external shades should include a manual override in case of breakdown or power failure.
In UK, architectural aluminium façade specialist, Technal, has launched its new brise soleil sun shading system, which provides highly efficient solar control and the highest standards of architectural aesthetics.
The Suneal system, already used extensively internationally, is a multi-functional addition to the façade which will protect occupants from glare from the sun, control solar gain, optimise natural light and enhance any building envelope with its stylish appearance and visual appeal.
Suneal uses passive solar protection to reduce the reliance on mechanical cooling systems, generating reductions in energy consumption.
It allows high levels of natural light into the building and has the option of fitting photovoltaic blades for the supply of renewable energy to the building whilst providing effective solar control.
Source : Construction Magazine; Technal; Kingfisher Louvers; Whole Building Design Guide; Passivent Limited and Warema International
(this article written for 1BINA.my)