The Healthy Humidity Level for Your Home

Go deeper: Full evidence, calculator and printable cheat sheet: The Healthy Home Humidity Guide

Rung 1: Measure it (cheap)

You cannot manage what you do not measure. A small digital hygrometer costs little and shows relative humidity (RH), the amount of moisture in the air compared with the most it can hold at that temperature. Put one in the bedroom and one in the living room, and note readings in the morning and evening for a week.

Cold rooms show higher RH than warm rooms with the same moisture, so check the room where the problem is, not just the hallway.

Rung 2: Know the numbers

The review is Arundel and colleagues, 1986, which gives the 40 to 60 percent band. NHS hospital guidance on dust mites advises keeping indoor humidity under 50 percent (but over 30 percent) if necessary using a dehumidifier. So if dust mite allergy is your main concern, a lower setting in the 40s may suit you better than 55 percent; Dryzen's range is adjustable between 40 and 70 percent.

Rung 3: Lower it without a machine

• Ventilate where moisture is made: extractors in kitchen and bathroom, run during and after use.
• Dry washing outside, or in a ventilated room, not on radiators in a closed room.
• Heat steadily; warm air holds more moisture before it condenses.
• Fix leaks first; no humidity target is reachable with a leaking roof or pipe.
• Keep trickle vents open and furniture off cold external walls.

Rung 4: Hold it steady with mechanical control

If habits and extraction are sorted and the readings still sit high, a dehumidifier can hold the house in the band. Dryzen is a loft-mounted unit that removes up to 12 litres a day, covers up to 150 m2 per unit, and has a smart app with temperature and humidity monitoring (it needs 2.4GHz Wi-Fi and internet). The yearly Gold membership includes a free humidity monitoring plan, where we alert you if there are any issues with your home or the dehumidifier. It needs a loft, is for owner-occupied homes, and is not suitable for rentals unless the landlord authorises the changes.

What humidity control can and cannot do

Keeping humidity down helps stop the conditions that mould, dust mites and some damp-loving insects need. It is not a pesticide and it does not kill anything outright.

• Mould already growing must be cleaned off. Controlling humidity stops it coming back.
• Dust mites do poorly when mean daily RH stays below about 50 percent, which is why the NHS guidance above points to that figure.
• Silverfish and booklice are described by university extension guidance as indicators of excess moisture, and reducing humidity helps control them.
• Bed bugs, fleas and spiders are not controlled by humidity. If you have them, get proper treatment.
• Health effects are real but not a cure: the WHO review found damp and mould linked to more respiratory symptoms, allergies and asthma, which is a reason to fix damp, not a promise that a machine will cure anyone.

In Chatham and the Medway Towns

Medway homes vary in how easily they hold the band. Solid-wall terraces near the Dockyard, such as those in Brompton and Gillingham, tend to read higher in cold months. Airtight estate houses in Rainham or Lordswood can read high after showers and laundry. Measure first, then decide what to change.

Questions we are asked

Related guides

• Condensation on Windows: What It Is Telling You
• Bathroom and Kitchen Extraction That Actually Works
• Black Mould in Bedroom Corners: Find the Cause

Local help

• Damp, mould and condensation help in Brompton
• Damp, mould and condensation help in Rainham
• Damp, mould and condensation help in Lordswood

Sources: Arundel et al. (1986), Indirect health effects of relative humidity in indoor environments; Cambridge University Hospitals NHS: Dust mites in your home; WHO Guidelines for Indoor Air Quality: Dampness and Mould, executive summary; University of Florida IFAS: Booklice and silverfish; GOV.UK: Understanding and addressing the health risks of damp and mould in the home. The Healthy Home Humidity Guide (Dryzen).