Ventilation and extractor fans
CFM ratings, building regs, and why this is the most overlooked element.
At a glance
Quick Checklist
Key points at a glance
- 1Minimum 15 l/s extract rate for bathrooms
- 2Must vent to outside, not into loft
- 3Timer or humidity sensor recommended
- 4Under 30dB for quiet operation
- 5Check building regs for windowless rooms
Questions to ask your installer
Take these to your next conversation with your fitter
- 1What's the correct fan size for my bathroom volume?
- 2Where will the external vent be located?
- 3How will the duct run affect the fan's actual performance?
- 4Should the fan have a timer, humidity sensor, or both?
- 5Is the wiring adequate for a new fan?
- 6Will this meet building regulations for my bathroom?
💡 Tip: A good installer will welcome these questions. If they dismiss them, that's a red flag.
💡Myth vs Reality
Common Myth
"Opening a window is as good as an extractor fan"
The Reality
Windows are unreliable (people don't open them in winter). Fans extract consistently and meet building regs.
Common Myth
"Any extractor fan will do the job"
The Reality
Undersized fans struggle to clear moisture, leading to mould and damp problems.
What to look for
- •Extract rate in litres per second (l/s) - minimum 15 l/s for bathrooms
- •Timer and humidity sensor options to run after you leave
- •dB rating for noise level - under 30dB is barely audible
- •Building regs require extract ventilation in bathrooms without windows
Common mistakes
- •Choosing a fan based on looks rather than performance
- •Undersizing the fan for the room volume
- •Venting into the loft space instead of outside (causes damp)
- •Long duct runs that reduce actual extract performance
Quality considerations
- •Cheap fans are loud and fail within a few years
- •Quality brands like Vent-Axia and Manrose are worth the premium
- •DERA-rated fans meet the latest building regulation standards
- •Consider whole-house ventilation systems for better air quality
Planning a bathroom right now?
Submit your project for a free 3D layoutNo obligation. Planning support is always free.
Trusted by verified installers
Our guides are shaped by real installer experience and the most common homeowner mistakes — without pushing any specific brand or purchase.
The Plan My Bathroom Promise
Plan with clarity first. Products and partners are always optional.
No obligation to purchase
Planning support is always free
Planning-first approach
Get clarity before making decisions
Verified professionals
Optional introductions when you're ready
Transparent guidance
Honest advice, no hidden agendas
Found this helpful? Share it:
This guide is written to help you make informed decisions, not to sell you anything. Always discuss your specific situation with a qualified installer.