Concrete was used as a sustainable material by more than three out of every four design professionals recently surveyed about their preference of materials for sustainable design. According to a market research study conducted by the Portland Cement Association (PCA), 77 percent of surveyed architects, designers, engineers, and other design professionals said they chose concrete as their sustainable material for recent projects. Respondents ranked concrete favorably for its energy efficiency, durability and reduced maintenance. Survey respondents ranked the level of importance of 22 attributes when selecting building materials. Energy efficiency was perceived as the most important attribute when selecting a building material with a mean rating of 4.5 out of five, followed by durability (4.4), and aesthetics (4.2). When asked which building material they preferred to meet those attributes, concrete was the most common response for energy efficiency and durability.