Symptoms
- One or more rooms consistently colder than the rest
- Upstairs colder than downstairs or vice versa
- Problem is consistent, not occasional
Likely causes
- CommonClosed, blocked, or undersized vents in the cold roomFurniture or rugs over vents, or dampers partly closed, starve a room of warm air.
- CommonLong duct runs losing heat before reaching far roomsRooms farthest from the furnace naturally get cooler air by the time it arrives.
- CommonPoor insulation in that room (exterior wall, above garage, large windows)Heat loss can outpace what the duct is delivering.
- PossibleDuct leaks in unconditioned spaces like an attic or crawlspaceLeaky ducts can dump heated air before it reaches the room.
- PossibleSingle-zone system without dampers to balance roomsA one-zone system heats everywhere the same amount regardless of individual room needs.
What to do
- Make sure vents in the cold room are fully open and not blocked by furniture, curtains, or rugs.
- Close vents partway in already-warm rooms to push more airflow toward cold ones.
- Check for drafts around windows and doors in the cold room and add weatherstripping if needed.
- If you can access the attic or basement ducts, look and feel for obvious leaks or disconnected sections near the cold room's duct run.
- Consider a door-mounted or portable space heater as a stopgap for one persistently cold room.
- If imbalance is severe or whole-house, ask a technician about duct sealing, balancing dampers, or a zoning system.
Tools and parts
- Flashlight
When to call a pro
Call an HVAC technician about duct balancing, sealing, or zoning if closing/opening vents doesn't fix a persistently cold room.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.