Homes in the U.S are responsible for 13 percent of the country’s total greenhouse gas emissions. Building net-zero homes would help bring that number down. But, so far, building such energy efficient homes is expensive. One home-building company is changing this. Deltec homes is designing prefab homes that cut out two-thirds of the energy used in a typical house of the same size while using rooftop solar to power the rest. The homes are built in factories in just a few days to keep raw materials unexposed to the weather so they will last longer, and are customized to be as sustainable and efficient as possible based on the location where the home will be placed. And by making the home out of prefab materials, Deltec can keep the prices of homes down, with the cheapest model available selling for around $150,000. The homes range from 800 square feet to around 2,100 square feet.