The dark metal surface heats up when exposed to the sun. Coupled to most ventilation fans, the collected, heated outside air enters the building, reducing energy costs for heating. A ventilation fan creates negative pressure in the wall cavity to draw air through these holes. The hot air rises to the top of the wall and is ducted to the nearest fan.
Hot air is ventilated through holes in the top of the cladding.
Air-tight buildings may have lower heating bills but sometimes at the expense of indoor air quality. It requires energy to heat this air.