Jalousie is a door or window shutter having adjustable horizontal slats for regulating the passage of view, air and light. The word Jalousie literally means jealousy perhaps because one can look through the screen without being seen. The word derives from old French gelosie which means a latticework screen. The earliest reference to Jalousie dates back to around the 16th C. Louvers of wood perhaps originated in the middle ages to cover chimneys for escape of smoke, and also for to keep rain and snow out while allowing air ventilation through roof lanterns meant for illumination.
Jealousies or Louvers are both fixed and movable systems. These are impossible to seal completely, so are not very energy efficient systems. For the same reason these are well suited for verandah openings of tropical buildings to let in air and light. Jalousie is not considered a security tight opening.
Fixed Jealousies or louvers have a small gap -usually downward between its slats. The downward gap reflects light towards the ceiling, often creating distracting movement of shades. Downward system is called Awning-louvers systems. Contrary to the jalousie upwardly open, are called Hopper louvers systems. Awning systems are top-hung, whereas Hopper systems are bottom-hung.
Movable louvers open upwards, downwards and both ways. The opening gap and angle both are adjustable, individually or simultaneously.
Louvers are ‘shutter elements’ within a door or window shutter. Such louvres are either fixed or movable, in horizontal or vertical positions. Louvers like panelling -fixed system with no gap (inclined and over-lapping edges like shingles), are also used in doors and windows’ shutters.
Jealousies are placed within a shutter for part of a section as a ventilator or as an additional full-length door or window shutter, over the glass or solid panel shutters.
Louvers provide visual privacy and control the passage of air, and also shed the rains. Louvers also control the amount of direct sun light and cut off the reflected light component by baffling and reflecting it. Louvre surfaces are treated to improve or reduce the reflection of light, solar radiation and for sound attenuation. Micro width louvres are incorporated into narrow space between glass panes such as air-crafts.
Louvres are also used in many utilities such as air distribution and sound proofing systems. Louvres as fixed slats are used in toilet doors, walk-in-wardrobe doors, kitchen cabinets. Mediterranean homes have louvered door and window shutters as secondary doors. Louvered panels are used in tropical houses to cover up the verandah like spaces.
Louvres as an appendage are also placed on the exterior face as Brise soleil and on inside as Venetian blinds. Alvar Aalto, Finnish architect has used the fixed and movable louvres in several of his buildings.
Pivots were the first movement mechanisms for doors and windows. Pivots were technologically easy to devise, but difficult to install and maintain. Early windows like the pivot doors opened inwards. Even today pivot windows opening fully or partly inward or outward are difficult to weather-seal. Double-hung sash windows have ‘hopper or awning; like pivoted shutter for opening a sash to clean and maintain its outer face.
Horizontal pivot louvre windows are used in Industrial sky lights. Here the upper section is made slightly larger-heavier than lower section by minute off-centric positioning of the pivot. The upper section being larger is heavier, so opens out or inward as soon as the catch that holds the shutter is released.