Dehumidifiers are one of the most common things people buy when damp or mould appears. Used in the right situation they help a lot. In the wrong situation, they can make a room feel better while the real problem carries on behind the scenes.
Where dehumidifiers help
- Condensation: lowering humidity reduces condensation on windows and walls, especially in flats with limited ventilation
- Drying washing indoors: running one in the room where clothes are drying removes a lot of moisture
- Drying out after a flood: professional drying uses dehumidifiers to remove moisture from walls and floors
- Short-term relief while a longer-term solution is put in place
Where they don’t fix the problem
- Rising damp: moisture coming up from the ground through a failed damp proof course
- Penetrating damp: damp caused by defects in walls, roofs or windows
- Plumbing problems: water from pipes, appliances or a flat above
- Salt-contaminated plaster: salts left by rising damp attract moisture from the air and keep walls damp
In these cases a dehumidifier may make the air feel drier, but the underlying damp remains, and damage such as decayed plaster or rotting timber can continue.
Signs you need more than a dehumidifier
- The tank fills up every day and the damp never improves
- Damp patches are at low level on walls, or appear after rain
- Tide marks, salt deposits or crumbling plaster
- A musty smell from under the floor
A longer-term answer for condensation
For persistent condensation, ventilation is usually a better long-term answer than running a dehumidifier every day. Effective extraction in kitchens and bathrooms and whole-house solutions such as positive input ventilation tackle the moisture where it is produced.
If you are not sure what is causing the damp, our surveyors will find out. Read more about condensation control and damp proofing.
