Short answer
Start with the vent in that room: open it all the way and move furniture, rugs and curtains off it. Keep the door open, or make sure air can get out under it. Close the curtains at night and seal drafty windows. Replace a dirty furnace filter. If the vent barely blows, a technician can check for a closed damper or a leaky duct.
Safety first
If you use a space heater in the meantime, keep it three feet from anything that can burn, plug it straight into the wall and turn it off when you leave the room.
How to warm up the one cold room
1One room stays cold
The rest of the house is cozy, but this room is not. Often the warm air is there, it just cannot get in.
Read all the steps
- One room stays cold. The rest of the house is cozy, but this room is not. Often the warm air is there, it just cannot get in.
- Open the vent all the way. Find the vent in that room and slide its lever or turn its wheel until the slats are fully open.
- Move furniture off the vent. A couch, bed, rug or long curtain over the vent blocks the warm air. Leave the space in front of it clear.
- Keep the door open. Air has to get out for warm air to come in. If the room has no return grille, a closed door chokes the airflow.
- Stop the drafts. Close and lock the windows, close the curtains at night and seal gaps with weatherstripping.
- Warm and cozy again. Give it an hour. Still cold, or the vent barely blows? A technician can check the dampers and the ducts.
- Still not fixed? Call an HVAC contractor Especially if: the vent is open and clear, but barely any air comes out.
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Why it happens
A closed or blocked vent and a closed door are the usual causes. Rooms far from the furnace, over the garage or with big windows lose heat faster. Inside the walls, a crushed or disconnected duct, or a damper that was closed, can starve the room of air.
Check the dampers on the ducts
In some homes the ducts near the furnace have small levers called dampers. The lever points the same way as the plate inside: along the duct is open, across is closed. If the duct to the cold room is closed, turning the lever to open is safe. Not sure which duct goes where? Ask a technician.
What not to do
- Do not close vents in the warm rooms to push air to the cold one. It cuts the total airflow and can make the furnace overheat.
- Do not cover vents with rugs or furniture.
- Do not run a space heater on an extension cord or leave it on while you sleep.
When to call an HVAC technician
- The vent is open and clear, but barely any air comes out.
- The room is still much colder after you open the vent, the door and the dampers.
- Several rooms are cold, or the furnace runs all the time.
- You find a duct that is crushed, loose or disconnected.
Frequently asked questions
Why is one room in my house colder than the others?
Usually the vent is closed or blocked, the door stays shut, or the room loses heat through windows and outside walls. A closed damper or a duct problem comes next.
Should I close vents in rooms I do not use?
No. Closing vents cuts airflow through the whole system and can make the furnace overheat or shut off early. Keep them open.
How do I get more heat into a cold room?
Open its vent all the way, clear furniture off it and keep the door open. Seal drafts. If that is not enough, a technician can balance the dampers so more air goes there.
Does closing the door make a room colder?
It can. Without a return grille in the room, a closed door keeps air from flowing back, so less warm air comes in. A gap under the door helps.
How do I know if a duct is disconnected?
Very weak airflow from one vent, a dusty smell and higher heating bills are common signs. A technician can find the duct and seal or reconnect it.