You can buy filters that are designed to be placed directly under each floor register. This gives you real, localized, room-by-room control. These filters come with a self-adjusting cardboard frame that allows you to simply lift off the register cover, push the filter into the duct and the flaps on the filter will hold it nicely in place. Replace the cover. Remember, they will eventually clog up with all the stuff they catch, so if the heat slows down in that room, remember to change the filter. For those of you who like a very light fragrance in the house, you can get scented versions of this filter. In fact, this is an energy-efficient way to give different rooms of your house different scents or no scents at all, according to your tastes.