While scientists around the world are busy developing various hi-tech methods to achieve solar control, a design feature as venerable and commonplace as the venetian blind could still be one of the best solutions at hand.
Solar control can be critical to the sustainability and efficiency of a built environment, as its impact upon indoor temperature levels can significantly reduce the load on HVAC systems and associated consumption of electricity.
Given its significance for building efficiency, a range of new window technologies for enhancing the solar control of indoor environments has recently emerged, including smart windows that can darken or brighten automatically, and organically inspired bio-windows that emulate the vascular structure of plants.
The systems are still at an incipient phase of development or adoption, however, and may still prove to be unwieldy and expensive in practice. The premium they require could add significantly to the cost of large-scale buildings or skyscrapers that are equipped with vast panoplies of window installations.
Solar control is a simple matter at its essence, involving modulation of the heat gain produced by the sun’s radiation while simultaneously permitting the ingress of sufficient levels of natural daylight free of disruptive levels of glare.
Often, a simple issue can be addressed by means of an equally simple solution, and in the case of the solar control for windows, one is already at hand in the form of a feature as common and convenient as the venetian blind.
The slats of exterior venetian blinds can be adjusted to a number of preset positions in order to respond to the full range of different solar conditions, permitting the control of heat gain while still allowing ambient light to penetrate the indoor environment.
The effect of the venetian blinds can be further adjusted by varying the width of the slats from roughly 50 to 150 millimetres, with the increased size resulting in greater exposure to solar radiation by producing larger spaces when slats are in the open position.
The blinds can be employed at either extreme of a building’s solar control needs. When fully shut, they are commensurate with a solid wall, completely preventing the penetration of solar radiation, even should the sun be situated at horizon level.
They can also be dispensed with completely by means of retraction, however, permitting full exposure via windows to whatever ambient sunlight remains available.
While the solidly physical nature of venetian blinds makes them an extremely effective means of achieving solar control, this characteristic can also impede or restrict their usage under certain conditions.
Exterior venetian blinds have a definite impact upon the aesthetic appearance of building, which must be taken into account during the design process. Even when retracted, the blinds will affect a building’s external appearance due to the presence of pockets or head boxes into which the slats will retract.
Another major limitation of exterior venetian blinds remains their vulnerability to strong wind conditions. The blinds will need to be retracted or placed in the open position when wind levels become too strong in order to prevent them from moving around, which can either impede their effectiveness or serve as an annoying distraction to those inside.
This susceptibility limits restricts their usage to the lower levels of a building, usually up to no greater than the 12th storey. At higher levels, the blinds may need to be switched to an indoor position, or installed within a double façade.