Air conditioning alone accounts for 12%-15% of global energy usage, while CO 2 emissions from air conditioning account for "13.7% of energy-related CO 2 emissions, approximately 52.3 EJ yearly" or 10% of emissions total. Air conditioning applications are expected to rise, despite their negative impacts on energy sectors, costs, and global warming, which has been described as a "vicious cycle." However, this can be significantly reduced with the mass production of low-cost PDRCs for indoor space cooling. A multilayer PDRC surface covering 10% of a building's roof can replace 35% of air conditioning used during the hottest hours of daytime.