What humidity should my home be? A simple UK guide

A humidity monitor turns a vague damp feeling into a number you can act on. Here's what that number means.

What relative humidity means

Relative humidity (RH) is how much water the air is holding compared with the most it could hold at that temperature. Warm air can hold more water than cold air, which is why the same air that feels fine in a warm living room leaves water on a cold bedroom window.

What to aim for

Around 40 to 60% is widely recommended for homes. As a rough guide:

• Below 40%: on the dry side. Some people notice dry skin or a scratchy throat.
• 40 to 60%: comfortable for most people, and harder for mould to get going.
• Above 60 to 65% for long periods: condensation and mould become more likely, especially on cold walls and windows.
• Above 70% most of the time: a room that needs attention.

Short spikes are normal. Humidity jumps when you shower or cook and should fall again within an hour or so with the fan on or a window open. It's the rooms that stay high that matter.

How to measure it properly

• Put the monitor at roughly head height, away from radiators, kettles and direct sun.
• Give it time to settle after moving it.
• Check morning and evening for a few days rather than relying on one reading.
• Compare rooms. The damp room is often the one with the door shut, the fewest heat sources or single glazing.

If the reading stays high

1. Ventilate more: trickle vents open, extractor fans on, a window open for a short spell each day.
2. Cut moisture at the source: dry washing outside or in one ventilated room, lids on pans.
3. Keep the heating steady so walls and windows don't get very cold.
4. Add moisture absorbers to problem rooms and wardrobes, or a small dehumidifier where absorbers can't keep up.

If humidity is normal but you still have damp patches, the cause may be a building problem rather than condensation. See Condensation or damp? How to tell the difference.