What is an external screen blind?
An external screen blind (in Dutch simply called a screen) is a type of exterior solar shading in which a fabric is lowered vertically in front of a window or glazed door. The fabric is rolled up in a box (cassette) above the window and runs in side guides, so that it hangs taut in front of the glass. A screen keeps solar heat out but, depending on the fabric, still lets through daylight and part of the view.
Variants:
- Screen with cable or channel guides: the fabric is held in place at the sides by cables or profiles.
- Zip screen: the edges of the fabric have a kind of zip that runs in the side guides. The fabric is therefore held all round, is more resistant to wind and there are no light gaps along the sides.
- Operation: with a crank, an electric motor with switch or remote control, or automatically with a sun and wind sensor.
Fabric types: most screen fabrics are made of glass fibre or polyester with a plastic coating. They differ in colour and openness (the percentage of small openings in the weave). A more open fabric gives more view, a denser fabric blocks more light and heat. Blackout fabrics are also available.
Application
Screens are used against overheating in homes, especially on sunny and west-facing facades, for sliding patio doors, dormers and large areas of glass.
Why outside works better than inside: exterior shading blocks solar radiation before it passes through the glass. Interior shading, such as a roller blind, only catches the heat once it is already inside. Exterior shading is therefore much more effective against a hot house.
Tips for choosing:
- Fabric colour: a dark fabric gives better visibility outwards from inside; a lighter fabric reflects more heat. Ask the supplier for the total solar energy transmittance (gtot) of the combination of fabric and glass.
- Wind resistance: on high or windy facades choose a zip screen and let a wind sensor raise the screen automatically.
- Recessed or surface-mounted: in new-build or renovation the box can be concealed in the facade or behind a sill or lintel. As a retrofit, the box is usually mounted on the facade.
- Power for the motor: plan the power supply in advance; an electrician connects it in accordance with the applicable regulations.
- Design rules and homeowners’ association: solar shading changes the appearance of the facade. In the Netherlands, check the local design rules (welstand) beforehand for a listed building or protected townscape, and the homeowners’ association (VvE) rules for an apartment. Other countries have their own rules; check with your local authority.
Related Terms
- Roller shutter
- Awning (marquise)
- Canopy
- G-value
- Window screen
- Window frame
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