Architectural trends have extended to modern outdoor designs that feature low maintenance without sacrificing style. Marcus Hiles has seen the desire for open-air spaces rise, as renters want areas that are both sustainable and financially viable. Conservation-minded options such as rainwater and graywater harvesting systems and permeable pavement are gaining traction. Via a rooftop collection system, rainwater harvesting funnels moisture falling from the air into a well, to then be treated and repurposed on-site. Graywater takes previously used household wastewater and recirculates it for rest rooms and other non-drinking purposes, greatly reducing the need for fresh water and lowering the amount of sterilization used. Permeable paving is a seemingly novel idea for sustainable construction, but actually dates back thousands of years to when people first developed roads by putting stones in beds over the ground. The design allows the rain to pass through small openings in between four layers of filtration (paving material, gravel, fabric, and sand) prior to being absorbed by the land below. This reduces runoff and pollution, manages the flow of storm water to gutters and drains, and provides local groundwater supplies and a skid-resistant surface for walkways, patios and driveways. Many attractive patterns for permeable pavement use crushed stone, brick, and recycled concrete.