Surprisingly, closing vents can actually waste energy and lead to costly repairs or early replacement. Your furnace is designed to heat a certain amount of space, and changing the area alters its performance. It’s better to leave doors open for more even airflow. If you have a room that’s too cold because it doesn’t have ductwork or it’s zoned differently than other rooms (like an addition or a sunroom), ask us about a ductless system that can deliver heat just were you need it with about 40 percent higher efficiency.