Some out-of-sight fans can be heroes in under-heated rooms. If yours is a forced-air system, try using duct booster fans to pull heated area more efficiently into the conditioned spaced. Such fans activate automatically whenever the furnace kicks on. With a great number and variety of models on the market, there are options to suit any household. Some plug into outlets, while others are hardwired. Simplest of all is a boost fan that sits on top of (or replaces) a register grille, conveniently plugging into an adjacent wall outlet while a built-in thermostat controls its operation.