What is the ideal humidity in a house in the UK?

Humidity is one of those things most people only think about once there’s a problem — streaming windows, a musty wardrobe, a patch of black spots in the corner of the ceiling. Knowing the number to aim for, and what your home is actually at, makes those problems much easier to prevent.

The short version: aim for 40–60%

Relative humidity (RH) is how much water vapour the air holds compared with the most it could hold at that temperature. For homes, the generally recommended range is 40–60%, with around 50% as a comfortable, safe target.

Humidity	What it means
Below 30%	Very dry. Can cause dry skin, sore eyes and static. Rare in UK homes.
30–40%	A bit dry. Usually only seen in well-heated, well-sealed homes in cold snaps.
40–60%	Healthy and comfortable for people and buildings.
60–70%	Too high if it lasts. Condensation and dust mites become more likely.
Above 70%	High risk of condensation and mould if it persists for days.

Why above 60% is a problem

At higher humidity, any surface colder than the air around it — single-glazed windows, the corner where an outside wall meets the ceiling, the back of a wardrobe against an external wall — can drop below the dew point. Moisture condenses there. Do that every night and you’ve created exactly the conditions mould needs.

Dust mites also thrive when humidity stays above about 60%, which matters if anyone in the house has asthma or allergies.

Humidity room by room

Different rooms behave differently, and short spikes are normal:

• Bathroom: will jump to 80–90%+ during a shower. Fine as long as it drops back below 60% within an hour.
• Kitchen: spikes while cooking, especially boiling pans without lids or the hob fan on.
• Bedrooms: often creep up overnight, especially with the door shut and two people sleeping. A reading of 60%+ in the morning is a common cause of window condensation.
• Living room: usually the most stable — unless washing is drying on the radiators.
• Rooms with drying laundry: a single load can release a couple of litres of water into the air.

Ideal humidity for a bedroom

Aim for 40–60% in bedrooms too, but check the reading first thing in the morning — that’s when it peaks. Two people sleeping with the door shut can push a small bedroom from 50% at bedtime to 65–70% by morning, which is exactly when windows start streaming. If that’s your pattern, see how to stop condensation on windows and the best dehumidifier for a bedroom.

Temperature changes the reading

Relative humidity depends on temperature. Cool the same air and the RH goes up, even though no water has been added. That’s why:

• a cold, unheated spare room often reads much higher than the warm living room next to it;
• humidity often rises overnight when the heating goes off;
• airing a room on a cold, damp-looking day still works. Outdoor air at 5°C and 90% humidity, warmed to 20°C indoors, drops to roughly 33% RH.

Keeping rooms at a steady, moderate temperature — rather than very cold with occasional blasts of heat — is one of the most effective ways to avoid condensation.

How to measure your humidity

You need a hygrometer. A basic digital hygrometer on Amazon (opens in a new tab) (paid link) costs very little and is accurate enough to tell 50% from 70%. A few tips:

1. Put it at head height on an inside wall, away from radiators, windows and the kettle.
2. Give it an hour to settle when you move it to a new room.
3. Check at different times — morning readings in bedrooms are the most revealing.
4. Consider a smart hygrometer on Amazon (opens in a new tab) (paid link) if you want to see trends over a week; the graph makes patterns obvious.

What to do if it’s too high

If your readings are regularly above 60%, start with the free and cheap fixes in how to reduce humidity in a room. If they’re not enough — or there’s already condensation every day — these are the signs you need a dehumidifier.

What to do if it’s too low

Dry air is unusual in UK homes, but it can happen in very well-insulated flats during cold, dry spells. Drying a little washing indoors, keeping houseplants or using a humidifier on a low setting will lift it. Avoid overdoing it — it’s easy to swing straight back into condensation territory.