Besides over 400 buildings, Wright contributed numerous architectural design concepts, many of which are still in use today.  One of these contributions was the idea of using unfinished materials. Wright would construct walls of boulders or rocks from around the building sites without ruining the natural beauty of the rock.  He also popularized the use of concrete as a building material.   He used windows to decorate and accentuate the outdoors and to assist in heating, supporting his goal of form fits function.  He was also the first to use roof overhangs to help with heating and cooling.  The overhangs would block the sun in the summer, while letting it in during the winter when the sun is lower in the sky.  With his Prairie Style, he introduced asymmetrical floor plans like the open floor plan.  Before Frank, houses were built with very boxy, symmetrical floor plans.