fan extraction rate for ensuite

[arcturus]

Hi

Wonder if you can advise. I'm putting in a small windowless ensuite off the bedroom (shower, WC, basin) and the drawings specify a fan capable of extracting at 30 litres/sec. I can't see anything in Part F of the (English) Regs that requires this much, and the requirement for 4 air changes/hour will be met easily by a fan with 15 litres/sec.

Appreciate I'll need a 15min overrun, but do I really need 30 litres/sec?

Is it likely to be different in Scotland, where I am?

Thanks

 

[stem]

English Building Regs can be viewed on line by clicking here. The required extraction rates tables are shown on page 19. Sorry. I don't know about Scotland

 

[bernardgreen]

And remember that the air taken out of the room by the fan has to be replaced by air coming into the room normally by a vent in the door. ( or a gap between door and floor ). The more difficult it is for air to enter the room the less air the fan will extract from the room. The actual air flow depends on things like length of duct, whether the duct is smooth wall or corrogated wall and air temperature. Sometimes the fan when installed can only achieve half the rated air flow.

 

[arcturus]

Thank you both. I'll check the clearance under the door.

 

[BigJon]

On a recent rewire (Scotland) the drawings stated 30l/s for WC's so I presume thats the norm.

 

[flameport]

15 litres per second is what a feeble and useless extractor costing £10 would do easily.

For a shower room, 15 l/s will be next to useless, so not surprising that 30 l/s is specified. Air changes per hour is also misleading, since in normal use, the fan won't actually be on for an hour or anywhere like it.