Why does my bathroom extractor leave the room foggy, and what should I do?
A bathroom extractor that cannot clear the steam after a shower is almost always one of three problems. The duct run is too long or too restrictive for the fan. The fan itself is undersized. Or the room has no path for replacement air to enter while the fan runs. Replacing the fan without addressing the underlying cause often disappoints.
What it usually looks like
These are the symptoms readers describe most often. None of them alone is diagnostic, but together they build a picture.
- Mirror remains foggy long after the shower
- Wet wallpaper or peeling paint near the ceiling
- Black mould around the extractor grille
- Bathroom door wet on the inside
Most common in: New-build flat · Victorian terrace · Edwardian semi-detached · Interwar semi (1920s–1930s)
Before you buy anything
Watch the house respond as you scroll.
These checks are listed in the order we would work through them. The illustration on the left changes with each one, so you can see what each check is actually addressing before deciding whether it is worth doing.
Warm wet air settles on the coldest surface and stays there. The window streams; mould follows.
Trace the duct from the fan to outside
Long flexible duct runs with bends can halve a fan's effective extract rate. A straight, smooth duct often makes a small fan perform like a much bigger one.
Confirm the fan's quoted extract rate against building regulations
A bathroom typically needs at least 15 litres per second of intermittent extract. Many old fans are well below this.
Check whether replacement air can reach the bathroom
A fan with no air path simply hums. Leaving the bathroom door slightly open during operation often solves it.
Look at the run-on timer setting
An extractor that switches off the moment the light goes out cannot clear a humid room. Twenty minutes of run-on is a common upgrade.
Decide whether continuous low-rate extract is appropriate
A small continuous fan running at low speed prevents build-up rather than chasing it. It is often quieter and more effective overall.
Products that may help
Only consider these once the checks above have been ruled out. A product fitted into the wrong cause is rarely satisfying.
The cheapest answer to bathroom extractor not coping with steam is usually the one that addresses the cause rather than the symptom. The list above is in the order we would work through it, because the checks at the top tend to rule out the most expensive mistakes further down.
Run the Home Comfort Score for this room
A two-minute reading gives you a number to compare against after each improvement, so you know what is actually working.