Bathroom Extract Ventilation Done Properly
Most bathroom damp complaints are ventilation problems wearing a disguise.
Most bathroom damp complaints are ventilation problems wearing a disguise. An extract fan that is undersized, poorly ducted or terminated into a loft will produce mould however new the bathroom is.
Duct length ruins performance
A fan rated in free air loses much of its output through several metres of flexible duct and two bends. Rigid duct and short runs preserve it.
Terminate outside, always
A duct dumping into a loft space transfers the moisture rather than removing it, and causes exactly the damage people were trying to avoid.
Run-on and humidity control
A humidity-sensing fan with a run-on timer clears the room properly after a shower instead of stopping the moment the light goes off.
Questions we get asked
Why is there mould despite a fan?
Usually the fan cannot achieve its rated extract because of duct resistance, or it stops before the room has cleared.
Do I need a fan if I have a window?
Building Regulations set the requirement, and in practice a fan clears a shower far more reliably than an open window in winter.
Can the fan connect to the light?
It commonly does, with a run-on timer so extraction continues after the room is vacated.