According to Wikipedia, A louver (in American English) or louvre (English) is a window blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain, direct sunshine, and noise. The angle of the slats may be adjustable, usually in blinds and windows, or fixed. This century the use of concrete louver vents has become soo popular in residential, commercial and institutions buildings due to their durability. kafum engineering a construction machinery manufacturing company in Kenya has been in this field for long and is the only company in Kenya that can be trusted to fabricate louver block molds that guarantee precise louver vents molding

Louvers originated in the Middle Ages as lantern-like constructions in wood that were fitted on top of roof holes in large kitchens to allow ventilation while keeping out rain and snow