Why is upstairs colder than downstairs?

Warm air rises, so upstairs should if anything be warmer. When it is not, something is preventing heat reaching or staying there: unequal flow through the heating system, poor insulation above, or cold air coming in.

What you'll need

• Radiator bleed key
• Two thermometers (optional)
• Adjustable spanner (optional)

Step by step

1. Feel every radiator once the heating has been on an hour.If downstairs radiators are hot and upstairs are lukewarm, the system is unbalanced. That is the most common cause by a distance.
2. Bleed all upstairs radiators first.Air collects at the highest points of a heating system, so upstairs radiators are where it accumulates. Check boiler pressure afterwards.
3. Balance the system if bleeding does not fix it.Close all lockshield valves, then open them progressively — least for radiators nearest the boiler, most for those furthest away. It forces flow to the far end.
4. Check for stuck TRV pins upstairs.Remove the valve head and confirm the pin moves freely. A seized pin keeps a radiator permanently cold.
5. Check loft insulation depth.Around 270mm is the modern standard. Older houses often have far less, and heat loss through the roof is the largest single loss in most homes.
6. Look for draughts from the loft hatch and around pipework.An uninsulated, unsealed loft hatch is a direct opening to a cold space, and it sits right in the ceiling of a landing.
7. Check the radiators are big enough for the rooms.Upstairs radiators are often undersized in extensions and converted rooms. If it is hot all over and the room is still cold, that is the answer.
8. Check curtains and furniture are not blocking them.A radiator behind a long curtain heats the window. It is a common and completely avoidable loss.

Tips

• Balancing needs the heating off and cold to start, and takes an afternoon of small adjustments. It is genuinely worth the time and costs nothing.
• Reflective panels behind radiators on external walls make a modest but real difference in solid-wall houses.
• If one bedroom is always cold and the rest are fine, that is a local problem — the radiator, the valve, or a specific draught.

Common mistakes

• Turning the whole system up to fix one cold area — It overheats everywhere else and raises the bill without addressing the distribution problem.
• Adjusting lockshields at random — Balancing is systematic. Random changes usually make the imbalance worse in a different room.
• Insulating the loft but not the hatch — The hatch is a hole in the insulation and sits directly above the landing. Insulating and draught-sealing it is cheap and immediate.

Questions people ask