Why Wood Framed Casement Windows Rot

Video shows problem with casement sashes.
Casement windows are windows with sashes that generally open with a crank handle and they are hinged at the side or top. All the top of the line casements windows are made of wood, some with an aluminum cladding on the exterior. The area that rots is the bottom of the sash and the bottom of the frame that is hidden when the sash is closed. If the window is not opened regularly and the area cleaned along where the crank mechanism is, the wood will rot.
Over time dust, pollen and everything from grass clippings to dandelion heads will get trapped in the narrow gap. When it rains it will get wet and it will not be long before there is deterioration that in turn will damage the window unit. Casement windows need to be cleaned regularly and may need to be painted every seven to ten years.