Thursday, 12 January 2012

Controlling Solar Heat Gain

Control of solar heat gain is a central tenet of Approved Document L2A. It is recognised as a critical element on new-build and refurbishment projects, particularly on commercial buildings.

Solar shading devices are often specified to simply modify the daylight entering a building or to help reduce the glare potential of windows. Perhaps more importantly, they are required to control the admission of direct radiation from the sun. If this is the case, then the positioning and colour of shading devices has to be a key consideration.


Positioning
Internal shading devices can only intercept the solar radiation which has already passed through the glass. A significant portion of the radiant energy striking an internal device is absorbed, some is convected and some is re-radiated into the room. This makes internal shading devices less effective for controlling solar heat gain than if they were applied externally.

External shading devices dissipate almost all of the convected and reradiated heat to the outside air. It is typical that the effectiveness of an external shading device is 30% greater than that of an internal one.

Colour
Dark coloured, internal Venetian blinds absorb 20% more heat than light coloured ones. With roller blinds the effect is even more pronounced and light colours give about 30% more protection than dark ones. When applied internally, bright metallic, white or light coloured solar shading devices should be used where possible, as they absorb less solar radiation and are less likely to re-radiate heat into the room or warm the air through convection.

Conversely, dark coloured external shading devices reflect less energy through the glass. The heat absorbed is lost by convection and re-radiation to the outside air. Therefore, dark coloured external shading devices perform better than light coloured ones.

Levolux thrives on the challenge of developing solar shading solutions, working to technically demanding specifications and designs. As the UK's leading solar shading specialists, Levolux has established itself as the architect's choice. For more information visit www.levolux.com.

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