Simply put, the manufacturer claims that the APEX Block is the most energy-efficient construction material on the planet. That's up for debate, but the product—made from recycled polystyrene and cement—is pretty cool. An average home built with the block keeps 2,830 pounds of polystyrene out of landfills, the company estimates. Cost: $20.25 per block. APEX Construction Systems. 800-252-8784. www.apexblock.com.