Venetian blinds regulate natural light and solar heat effectively because you can adjust their slat angle to the solar-radiation angle according to the season and time the day. The slats or fins of Venetian blinds are either bright white or polished aluminum when they are designed for controlling light and solar heat.
Venetian blinds install on either the windows’ interior or exterior. When installed on the window’s exterior, Venetian blinds increase comfort and reduce air-conditioning costs more than any other common window treatment. They are quite popular in Europe where many office buildings have no air conditioning. Exterior blinds admit less than 10% of the solar heat of a single-pane window when the blinds are fully closed. Interior Venetian blinds typically admit around 40% of the solar heat of a single-pane window, which is still quite good for an interior window treatment.
For large commercial windows, the blinds’ slats vary from 2 inches to 8 inches in width. The larger the width the greater the viewing area between slats. However, interior installations tend to be less than 4 inches because wider slats require too much space near the window. Some manufacturers offer large shaft-mounted exterior louvers that resemble large Venetian blinds. You can control Venetian blinds or shaft-mounted louvers manually or automatically.
Motors and automatic controls can reposition the slats of the exterior blinds as the sun angle changes, to regulate natural light and solar heat. The newest control options and blind designs can position the slats in a single large blind differently at the top and bottom of the blind. For example, the controls can close the slats at the bottom to block direct sunlight and open slats at the top to admit natural light in a building with an overhang that shades the window’s upper portion. Exterior installations are equipped with anemometer-controlled motors to sense wind speed and to retract the blinds into their housing during high winds. Occupants can also retract the blinds or control slat positioning to optimize light and solar heat in their work areas.
The controls can be as simple as switches, which adjust the slats or retract the blinds. Or the installer can program a series of buttons representing options such as morning, afternoon, full-open, full-closed. The most sophisticated controls sense brightness and direction of sunshine and adjust the slats for the best combination of natural light and reduced solar heat.