dehumidifier or extractor
A method comparison, not a brand roundup: when to extract vapour at source, when to dry room air, when continuous ventilation is the job. No model rankings.
Updated 2026-09-05 · 8 min read
Three families of kit treat different physics. Buying at random is the expensive way to stay stuck. This is a method comparison: no brands, no “best of 2026”.
Windowless bath, daily showers, mould on silicone: local extract beats a dehumidifier running in the lounge. Discharge outside, humidistat, door shut while in use.
Useful if measured RH stays high in the living room or bedroom (indoor laundry, little airing, sealed winter). Capacity is an estimate, not a model to copy. If stains climb from the skirting, it is the wrong tool.
It belongs in a project or a retrofit, or when vapour is structural (a very tight house). Qordac does not sell plant and has no invented partners: if a lead channel arrives, it will be labelled as such.
Start with the guided diagnosisNone, until you know whether the problem is bathroom vapour, wet room air or a wet wall. Diagnosis comes first.
Often yes, for indoor vapour. It does not close a leak, and it is not a purchase to make from a web article without a site visit.
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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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80–350 €
Useful if indoor air sits above ~60–65% and the cause is indoor vapour (showers, cooking, laundry), not a wall wet from below.
When: Measured high RH, window condensation, indoor drying, windowless bath.
Not when: Rising damp, leaks, stains that start at the skirting and climb.
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40–180 €
In a windowless bathroom this often beats a portable dehumidifier: it removes vapour at the source.
When: Bathroom mould, daily showers, poor air change.
Not when: It will not fix a thermal bridge in a bedroom.
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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
Dehumidifier: when it actually helps (and when it is wasted money)
Honest criteria for whether a compressor dehumidifier is the right tool. No ranking of untested models.
MVHR and humidity: when it belongs (and when it is another project)
What MVHR does to indoor vapour, what it does not do to rising damp and leaks, and why Qordac has no invented plant partners.
Mould in a windowless bathroom: extractor before dehumidifier
Why a portable unit in the lounge will not fix black silicone, and how to spec an extractor with a humidistat.
Indoor laundry: how much moisture it adds (and what to do)
A full wash can put litres of water into the air. When to air, when to dehumidify, when to move the rack.