Dehumidifier: when it helps, when it does not

A dehumidifier is a machine that condenses vapour out of air and collects it. It does one job, and it only does that job well if that job is your problem.

When it makes sense

• Hygrometer: persistent RH above ~60–65% in lived-in rooms.
• Recurring condensation and indoor laundry.
• Diagnosis pointing to indoor vapour, not rising damp.
• A cellar with saturated air and walls that are not climbing from below.

When it is the wrong move

• A wet band from the skirting up, salts, blowing plaster: structural track.
• A stain after rain on a roof pitch or a sill.
• Only the bathroom, ten minutes after a shower: extract at the source.
• You have never measured: you are buying noise.

Buying criteria (no top 10)

IgroCasa has no laboratory. We will not tell you “buy model X”. We will tell you what to read on the datasheet and where independent tests live. Consumer-test bodies publish lab results, usually behind a paywall: consult them, do not copy a ranking.

1. Litre capacity and test conditions (declared temperature and RH).
2. Airflow and a continuous-drain option if it must run for hours.
3. Noise: in a bedroom a low dB(A) figure beats “smart design”.
4. An adjustable humidistat. Without one the machine runs blind.
5. Refrigerant and filter care: hidden running costs.