Why is one room in my house colder than the others?

Finding that one specific room in your home is uncomfortably cold while the rest of the house remains warm is typically caused by over-supplying conditioned air, uninsulated exterior walls, or air leaks. If your HVAC duct balancing dampers are opened too wide for that specific branch run, excessive conditioned air will flood that room, dropping its temperature below the rest of the house. Additionally, rooms with multiple exterior walls, poor insulation, unsealed window frames, or drafty floorboards experience high thermal loss during colder weather. You can troubleshoot by measuring room temperatures and checking supply vent velocity. You can verify that your adjustments are successful when partially closing the supply damper for that cold room and sealing window drafts equalizes temperatures across your entire home.