The ADU’s cladding is stainless steel, making it resilient in all types of weather. “The D.C. metro area has four distinct seasons—it rains a lot, snows a lot, and it gets hot in the summer—so we wanted to create a unit that was adaptable and sustainable,” says David Lee, founder and CEO of prefab design company Aroom. The exterior of the main house contrasts the steel with its brick and light-blue siding, but the Yeons loved the idea of a refreshing and modern look for the backyard unit.