Architectural trends are extending to the outdoors, with a desire for designs which boast low maintenance and high style. Marcus Hiles has seen the demand rise for sustainable, cost-reducing open-air spaces. Rainwater/graywater harvesting and permeable pavement are the concepts leading the way. Utilizing a rooftop collection system, rainwater harvesting redirects rain that falls onto the roof to be stored in a well, then treated and repurposed on-site. Graywater repurposes previously used domestic wastewater to rest rooms and other non-drinking purposes, lessening the need for fresh water and lowering the amount of sterilization. Another seemingly novel idea for environmentally minded construction, permeable paving, actually dates back thousands of years to the time when people first made roads by putting stones in beds over the ground. The practice allows the rain to pass through small openings between four layers of filtration (paving material, gravel, fabric, sand) before becoming absorbed by the earth below. Its benefits include lowering runoff and pollution, controlling the flow of storm water to gutters and drains, replenishing local groundwater supplies and providing a skid resistant surface for walkways, patios and driveways; their many attractive patterns often incorporate crushed stone, brick, and recycled concrete.