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Hygrometer, damp and mould

Updated: October 2026

The hygrometer says 68%, the window is wet, and you want to know whether that number means mould. It means the air at the sensor was holding a lot of water vapour. It does not mean the wall has been tested, and there is no single UK legal indoor humidity band. The Centre for Sustainable Energy and East Herts Council publish different lines, and both are guidance. The Products Compared editorial team checked the twelve amazon.co.uk listings dated 15 October 2026. There was no laboratory test. If you buy through our Amazon links, we may earn a commission at no extra cost to you. The meters are on the [hygrometer comparison](/hub/climate-measuring/hygrometer).

The hygrometer says 68%, the window is wet, and you want to know whether that number means mould. It means the air at the sensor was holding a lot of water vapour.

Our top picks

Govee Govee H5075

Best overall

Govee Govee H5075
8.5/10about £9.98
View offer
TempPro TempPro TP157

Rank 2

TempPro TempPro TP157
8.6/10about £5.29
View offer
Thlevel Thlevel TBM-40 (6-pack)

Alternative

Thlevel Thlevel TBM-40 (6-pack)
8.0/10about £14.99
View offer
On this page
  1. 1.The bands UK bodies actually publish
  2. 2.The meter reads the air, not the plaster
  3. 3.A reading is not the repair
  4. 4.What a log can and cannot do in a rented home

The bands UK bodies actually publish

The Centre for Sustainable Energy says 40% to 60%, with mould risk above 60%. East Herts Council says 30% to 60% in cooler weather, and warns that a long spell above 70% encourages mould. Neither line is a statute. Where to put one is the how to use page.

The meter reads the air, not the plaster

Only the Tzone THS 701, at £160.99, prints dew point and wet-bulb, and it has no amazon.co.uk reviews and no numeric tolerance. Buying that logger does not dry a wall. A shelf at 55% can sit over a corner nearer the mid-60s if the external wall is much colder. A second meter, if you use one, belongs on that patch. The Property Care Association’s 10-point note, quoting BS 5250:2021, is a reason to look at the wall. It is not a figure these listings have been shown to measure, and a hygrometer does not mean you have complied with BS 5250. Wiping condensation off the glass does not change the reading an hour later if the air is still wet.
Govee Govee H5075

Testsieger

Govee Govee H5075
8.5/10about £9.98
View offer

A reading is not the repair

If the meter stays high and washing will not dry, the machine that extracts water is a different purchase from another screen. This page does not review dehumidifiers. GOV.UK’s guidance for housing providers says dampness can affect airways, lungs, eyes, and skin, and that the risk can rise even when mould is not visible. “How to rent a safe home” tells landlords to deal with dampness and ventilation. Consumer Rights Act 2015, section 9, is about whether the meter itself is of satisfactory quality, for example a unit stuck at 99%. It is a product complaint. It is not housing-disrepair advice.

What a log can and cannot do in a rented home

If you are a tenant, a week of readings can support a conversation: the bedroom stayed above 70% on East Herts’ long-spell warning, or above 60% on CSE’s risk line, at temperatures you also wrote down. It cannot prove the plaster is saturated, and it should not be framed as a confession. The Bluetooth or basic page is when that file is worth buying. If you buy a meter after this, buy one that prints a span and a tolerance you can explain. The buying guide is that checklist.

Common questions

What indoor humidity should a UK home aim for?
There is no single legal band. The Centre for Sustainable Energy says 40% to 60%, with mould risk above 60%, and 18 °C to 21 °C on its testing page. East Herts Council says 30% to 60% for comfort in cooler weather, and warns that a long period above 70% encourages mould. Say which source you are following. The meter reads air at the sensor. It is not a certificate that the home meets either page.
Does 60% RH mean mould, or is it 70%?
Both figures are published, for different warnings. CSE treats relative humidity above 60% as a mould risk. East Herts says a long period above 70% encourages mould, and uses 30% to 60% as the cooler-weather comfort range. A reading of 65% is above the first line and below the second. It is not a diagnosis, and 65% is not a legal average of the two.
Can a hygrometer prove the wall is wet?
It measures the air at the sensor. The Property Care Association, quoting BS 5250:2021, notes that a winter wall face can be about 10 relative-humidity points wetter than the room air. A normal shelf reading can therefore sit over a cold corner. The meter has not tested the plaster. The Tzone logger prints dew point and is still not a wall probe.
Does owning a hygrometer meet ventilation rules?
No. Approved Document F, volume 1, covers extract ventilation in homes in England, including kitchens and bathrooms. A bedroom hygrometer does not satisfy that guidance. It can show whether the air stays humid after you have used the fan. It cannot replace a missing extractor, and it is not a sign-off for building work.
What is the difference between a hygrometer and a dehumidifier?
A hygrometer displays relative humidity. A dehumidifier removes water. The Centre for Sustainable Energy keeps them separate and suggests setting a dehumidifier under 60% where possible, with a machine that can take at least 5 litres a day. Another meter does not empty the air. This page does not compare dehumidifier models.
When should I tell the landlord, and can a log blame a tenant?
Tell them if mould is more than a small patch or returns straight after cleaning, if it looks like a leak or salts, if a baby, an older person, or someone with a breathing illness is unwell, or if a landlord will not inspect. GOV.UK says sensors may help find homes at risk and must not be used to blame tenants. A log records air at the sensor. It does not replace the inspection.

Related pages

Best hygrometer

Hygrometer

Bluetooth hygrometer vs a basic meter in a UK home

Hygrometer buying guide: humidity span and tolerance

How to use a hygrometer: shelf, settle, then read it

Sources

Public UK sources used for this comparison. Listing prices, stars, and review counts are the amazon.co.uk lines from 15 October 2026.

  1. Centre for Sustainable Energy — condensation, damp and mould (retrieved 15 October 2026)
  2. East Herts Council — damp and mould (retrieved 15 October 2026)
  3. GOV.UK — health risks of damp and mould (retrieved 15 October 2026)
  4. Met Office — humidity (retrieved 15 October 2026)
  5. Property Care Association — control of dampness in buildings, January 2023 (retrieved 15 October 2026)
  6. Approved Document F, volume 1, dwellings (retrieved 15 October 2026)
  7. Consumer Rights Act 2015, section 9 (retrieved 15 October 2026)
  8. Yorkshire Housing — temperature and humidity sensor FAQs (retrieved 15 October 2026)