Many of us spend most of our time indoors, so it’s important to cultivate a space that’s a healthy one. A simple—and beautiful—way to do this is through houseplants; they add some green to your home while being an effective way to purify the air. NASA hardly seems like the organization that would give us insight into these types of plants, but in the late 1980s, the US government agency collaborated with the Associated Contractors of America (ALCA) to come up with a list of the most beneficia…