--- title: "What is the ideal humidity in a UK home? | Home Comfort Lab" description: "The humidity range that keeps a home comfortable and mould-free, and how to measure and control it." url: https://homecomfortlab.co.uk/damp/ideal-indoor-humidity/ --- # What is the ideal humidity in a UK home? The humidity range that keeps a home comfortable and mould-free, and how to measure and control it. By [Pete Harvey](https://homecomfortlab.co.uk/about/), editor. Updated 14 October 2026. This page links to Amazon. As an Amazon Associate I earn from qualifying purchases. [More about how this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). ![A calm living room with a hygrometer on a shelf reading in the comfortable green band, a plant and an open trickle vent.](https://homecomfortlab.co.uk/images/scenes/ideal-indoor-humidity.svg) > **The short answer** > > Aim to keep rooms between 40% and 60% relative humidity most of the time. Short rises after a shower or cooking are normal as long as they fall again soon after. Humidity that stays above 70% for days at a time is when mould starts to grow on the coldest walls and windows. ## What the numbers mean Humidity scale: below 40% is too dry, 40–60% is comfortable, 60–70% is damp, and above 70% is a mould risk. | Reading | What it means | What to do | | --- | --- | --- | | Below 40% | Dry. Can irritate eyes, skin and throats. No damp risk. | Turn the dehumidifier down or off, and don't over-ventilate in cold weather. | | 40 to 60% | Comfortable, and low enough to keep walls and windows dry in most rooms. | Keep doing what you're doing. | | 60 to 70% | Higher than ideal. Expect wet windows on cold mornings. | Ventilate more, and look at what's adding moisture. | | Above 70% | Mould can grow on cool surfaces if it stays this high. | Ventilate, find the source, and consider a dehumidifier. | These are the bands this site uses in its calculators. They are a working guide for everyday use, not a legal limit. ## What Building Regulations aim for Building Regulations guidance on ventilation in England (Approved Document F) sets humidity targets for new homes in the colder months. Averaged over time, the humidity in a room should stay below: - 65% averaged over a month - 75% averaged over a week - 85% averaged over a day The longer the period, the lower the limit. So a bathroom that hits 90% for half an hour after a shower is within the targets, while a bedroom that sits at 70% night after night through the winter is the room likely to grow mould. ## Why temperature changes the answer Relative humidity is how much water the air is holding compared with the most it could hold at that temperature. Warm air holds more than cold air. So the same amount of moisture gives a higher reading in a cold room than in a warm one, and the air right next to a cold outside wall or window is more humid than the middle of the room. Two things follow. Letting a room get cold pushes the reading up even though no water has been added. And a room that reads a comfortable 60% in the middle can still grow mould in a cold corner, behind a wardrobe on an outside wall, or round a window frame, because those surfaces are often a few degrees colder than the air you're measuring. [Mould risk checker](https://homecomfortlab.co.uk/tools/humidity-mould-risk-checker/): Put in a room's temperature and humidity to see the surface temperature at which walls and windows start to get wet. ## How to measure it You need a hygrometer: a small, cheap digital display that shows temperature and humidity. To get a reading you can trust: - put it at chest height on an inside wall, away from windows, radiators, kettles and the bathroom door - give it half an hour to settle after you move it - read it at the same time each day, ideally first thing in the morning before you open windows - check every room you're worried about, because one room can be much damper than the rest ### For checking one room TempPro TP50 Hygrometer Thermometer - **Type:** Digital - **Accuracy:** ±3% * Min/max memory A basic digital hygrometer with a stated accuracy of ±3% and a min/max memory, so you can see the highest reading overnight without getting up to check. [View on Amazon](https://homecomfortlab.co.uk/go/hy-basic-a/) [Manufacturer specs](https://temppro.com/products/tp50-digital-indoor-hygrometer-thermometer) More choices, including multi-packs and models that log readings to your phone, in [our hygrometer guide](https://homecomfortlab.co.uk/damp/best-hygrometer/). ## How to bring humidity down Start at the top. The first steps are free. 1. **Deal with moisture at the source.** Put lids on pans, run the extractor fan when you cook or shower and for a while after, and shut the kitchen and bathroom doors so the steam doesn't spread. 2. **Dry washing outside, or in one room with a dehumidifier.** Wet washing on radiators around the house puts a lot of water into the air. [How to dry clothes indoors without damp](https://homecomfortlab.co.uk/damp/dry-clothes-indoors-without-damp/). 3. **Keep a steady flow of fresh air.** Leave trickle vents open, and open a window for a few minutes after you get up. 4. **Keep rooms evenly warm.** Low, steady heat keeps walls warmer than short blasts, which lowers the humidity next to them. 5. **Run a dehumidifier** if a room still reads above 60% with the steps above in place. [Dehumidifier size calculator](https://homecomfortlab.co.uk/tools/dehumidifier-size-calculator/): Answer four questions about your home and get the dehumidifier size and type that suits it, with what it will cost to run. > If humidity stays high whatever you do, or a damp patch grows after rain, the water may be coming in from outside. [How to tell the types of damp apart](https://homecomfortlab.co.uk/damp/condensation-vs-rising-damp-vs-penetrating-damp/). If you rent, read [what your landlord must fix](https://homecomfortlab.co.uk/damp/damp-in-rented-home-landlord/). ## Sources - [GOV.UK: Approved Document F, Ventilation, Volume 1: Dwellings (2021 edition), Appendix B](https://www.gov.uk/government/publications/ventilation-approved-document-f) Checked 14 October 2026. ## Read next - [Humidity and mould risk checker](https://homecomfortlab.co.uk/tools/humidity-mould-risk-checker/) (Calculator) Enter your room temperature and humidity to see your mould risk and the temperature at which walls and windows start to get wet. - [What is a hygrometer, and which one should you buy?](https://homecomfortlab.co.uk/damp/best-hygrometer/) (Buying guide) A hygrometer measures how damp the air is, so you can act before mould appears. What it tells you, where to get one, and which to buy. - [Dehumidifier running costs: popular models compared](https://homecomfortlab.co.uk/damp/dehumidifier-running-costs/) (Running costs) What each popular dehumidifier costs per hour and per month at the current price cap, from its rated power. - [Dehumidifier noise and capacity table](https://homecomfortlab.co.uk/damp/dehumidifier-noise-and-capacity/) (Running costs) Every model we list, with its extraction rate, tank size, noise level and power, in one sortable table. --- As an Amazon Associate I earn from qualifying purchases. Links to shops are marked, and earning from them never decides what we recommend. [How this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). Running costs use 26.32p per kWh for electricity and 7.97p per kWh for gas, the [Ofgem price cap, Direct Debit average for England, Scotland and Wales](https://ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026) for 1 October to 31 December 2026.