Beta is a brand of Portuguese origin of a type louvered window which was used extensively for buildings in colonial Mozambique and Angola. It is also known as jalousie in other markets and appears to have been patented in the USA at the turn of the 20th century.
The basic operation of the Beta window allows for a series of louvered glass panels to be opened and shut via a lever. In Mozambique they have normally been installed on the intermediate landings of stairwells, public washrooms and education facilities whose facades are designed to allow the maximum possible light into compartments such as classrooms.
In residential applications, they have been found to be mounted above door frame where there is a separation of living spaces such as between kitchens, hallways, bedrooms and sitting areas. Their installation at these positions means there is no invasion of privacy under normal use.
When the louvered panels are in the open position, they allow air to pass between various compartments, including warm air that has risen to escape the compartments. This circulation allows for natural reconditioning of the air with warm, stale air moving out and being replaced by cool air.
Gradually these types of windows have lost their place in Mozambique. It is uncertain whether this is due to unavailability of the system, poor awareness of its existence or its propensity to be easily damaged.
In Mozambique, Beta windows can be found on buildings constructed after the 1950s, generally presenting some degradation of function or damage. Due to the tropical climate and the proximity to the salty air from the sea, many installations are not in operable condition.
The metal components were often coated with materials that succumbed to the harsh whether conditions causing them to degrade visually, mechanically or simply to break-off leaving no possibility for manipulation of the louvers. A second criticism has been its inability to provide a tight seal when in the closed position. Small gaps allowed insects and water to enter.
One of the main selling points was the extensibility. Glass louvers could be bought in standard sizes and cut for a perfect fit. Several units in standard sizes could then be installed next to each other.