How do I make a cold room warmer?

One consistently cold room in an otherwise warm house is a diagnosis, not just a discomfort. It usually means that room's radiator isn't getting its share of hot water, or the room loses heat much faster than the others. Both have identifiable fixes before you consider more heating.

What you'll need

• Radiator bleed key
• Draught excluder strip
• Reflective radiator foil (optional)
• Thermometer (optional)
• Heavy curtains (optional)

Step by step

1. Check the radiator heats evenly across its whole surface.Cold at the top means air — bleed it. Cold at the bottom means sludge. Cold overall means it's not getting flow.
2. Check the radiator valves are fully open.Both the thermostatic valve and the lockshield. A closed or partly closed lockshield starves the radiator.
3. Balance the system if this room is always the last to heat.Radiators nearest the boiler take the flow. Balancing restricts them so distant ones get their share — see the balancing guide.
4. Remove anything blocking the radiator.Furniture in front, long curtains hanging over it, or a shelf directly above. All divert the convection current away from the room.
5. Draught-proof the room: door, window, floorboards, skirting gaps.A cold room often has more air leakage than the rest of the house. Never block deliberate vents.
6. Fit reflective foil behind radiators on external walls.It reflects heat back into the room rather than into the wall. Cheap and measurably effective on solid walls.
7. Fit heavy lined curtains and close them at dusk.Windows are the weakest point in most external walls, and curtains meaningfully reduce the loss.
8. Check the room's insulation — particularly if it's above a garage or has an external corner.Rooms over unheated spaces and with two or three external walls lose heat much faster and may need insulation rather than more heat.
9. Only then consider a larger radiator or additional heating.If the room genuinely loses more heat than the radiator can supply, that's a sizing question — but check everything above first.

Tips

• A cheap thermometer in the cold room and one elsewhere tells you the actual difference, which is often smaller or larger than it feels.
• Rooms above garages and passageways are consistently the coldest in a house, because the floor sits over unheated space.
• A closed internal door keeps heat in the room but also stops warm air circulating into it. Experiment with both.
• Thick rugs on a solid or suspended timber floor make a room feel noticeably warmer for very little cost.

Common mistakes

• Adding an electric heater before diagnosing — Electric heating is expensive to run, and the underlying problem is usually free or cheap to fix.
• Long curtains hanging over a radiator — They channel the heat straight up behind them and out through the window.
• Furniture blocking the radiator — It absorbs the heat and blocks the convection current that warms the room.
• Ignoring balancing — A radiator that never gets hot enough is usually starved of flow, not too small.

Questions people ask