how to use a hygrometer
Where to put it, what error to expect from a cheap unit, how to keep a small log.
Updated 2026-09-01 · 6 min read
Without a hygrometer, “a damp house” is a feeling. With a cheap one you do not have a laboratory, but you have an order of magnitude and a log. It is the best cost-to-information purchase in the niche.
Both can be several points off. Decisions should follow the trend and room-to-room contrast, not 53% versus 56%.
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10–25 €
Without a relative-humidity number, every tip is guesswork. A €10–25 hygrometer is the first useful purchase — before any dehumidifier.
When: Always, as the first diagnostic step.
Not when: It does not replace a moisture meter or a rising-damp survey.
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12–40 €
Dew point needs temperature and humidity. One instrument cuts transcription errors.
When: When you want the calculators on your numbers, not a guess.
Not when: It does not measure moisture in the wall.
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20–80 €
Useful for a one-week log. A log beats a single reading, especially in winter.
When: Recurring condensation, night-versus-day doubts.
Not when: It is not a professional alarm system.
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Alduchov & Eskridge, 1996 — Magnus coefficients
Formule di Magnus-Tetens usate per stimare il punto di rugiada. Accuratezza tipica di frazioni di grado nel range indoor.
Accessed 2026-09-01
Damp at home: diagnose it before you buy anything
A step-by-step way to tell condensation, indoor vapour, rising damp and leaks apart. What to measure, what to watch, when not to buy a dehumidifier.
Window condensation: when it is normal and when it is a warning
Why glass runs with water, how to use dew point, and what changes between single glazing, double glazing and a cold reveal.
Rising damp: how to recognise it (and what not to buy)
Stains from the skirting, salts, crumbling plaster. How to tell it from condensation and when you need a surveyor.