In 2012, Dani Mouawad purchased a 1.55-acre piece of property in Chapel Hill, NC, then spent 10 months constructing a “sustainable, natural, health-promoting” house.

The building was made out of straw, clay, plaster, and lime, with a living roof made from topsoil displaced by the building’s foundation. Construction on the first of the property’s two buildings cost Mouawad, a pediatrician, “three times the cost of conventional materials,” he says, but what he spent in construction costs has more than paid off.