i have a bathroom with no ventilation/windows, about 10m cubed, and im going to fit a fan.

Does anyone know what spec building regs would require? Ie l/min etc.

Cheers!

Building regs wont need to know about it if its an existing bathroom.

Dont over complicate it.

if you have to have building regs involved ask the inspector what he would like to see done then you only have to do it once.
Ray

Minimum allowed by the regs is just a fan capable of 15l/s (about 54m3/hr), but that bare minimum is pretty inadequate imho unless you like the room to be dripping wet after a shower (assuming it has one) and be unable to see anything in the mirror. Sensible recommendations go up to 15-20 room air changes/hr for a bathroom with shower, so work that out for your room volume. I fit an inline loft mounted fan capable of 250m3/hr in my bathroom which is about 12m3 and it's great - room dry after a long hot shower. I dont even need the heated mirror I installed which I thought would be a god-send based on previous experience trying to shave after a shower in a bathroom with a piddly fan.

I'd over spec the fan (after years of battling against a moudly damp bathroom).

As said the minimum spec is rubbish.

I installed a speed controllable whole house ventilation in my house, when its on boost whilst having a shower the room stays 'fog' free. The best bit though is probably there is no noise whatsover from the system.

As said don't overcomplicate things but you are right to ask questions as even a very simple job as installing a bathroom fan has a few fairly important points to ensure effective extraction. A tiny 4 inch fan will work better than most people think if you follow the advice below.

If the fan is going on the ceiling and not on the wall, make sure you do as much of the ducting in solid pipe as possible because the flexi ducting thats available sags, if not supported properly (ie laid on a solid surface), and fills with water very quickly. This then stops your fan from working altogether. Also make sure your ductwork has a constant fall towards the outlet as you don't want cold water condensate dripping on your scone whilst showering! A more obvious tip is to mount the fan directly above the steam source.

If you are mounting it on the ceiling (recommended) you most likely won't have to worry about electrical zones unless you have very low ceilings. If its on the wall you will have to take the zoning regs into account. This is important but there is plenty of info on the web.

Another tip is to make sure there is adequate air flow under the door. If air can't get in how do you expect a little house fan to create an airflow?

Hope this helps.



[Edited on 30/7/10 by quinnj3]

Another way is to ditch the fan and rely on convection if you have space above the bathroom.
After trying to get a silent fan (without sucess) in my steamroom/shower I installed a 4" duct vertically up through the roof using soil pipe and a standard vented flashing.
The pipe needs to be insulated well for the thermosiphon effect to work and it keeps my room dry and mould free.
Part of the effectiveness is continuous low level ventilation rather than an almighty sook and nowt for 24 hours!
Well doccumented in building research docs under energy saving if you want to find out more.

cheers chaps, some good advice there. The bathroom isnt against an outside wall so needs 7m of ducting all in. The fan will be remote, halfway down the run.

Cheers all!

Theres no building inspector involved but i need it to comply incase they find out

[Edited on 31/7/10 by JoelP]

I wouldnt bother with building regs. Just do it and fit a bigger one. For them to work effieciantly though you need some way of replacing the expelled air. ie door ajar or window open.

Go to your local plumb/wholesale supplier and they will be able to advise you on which one would be suitable.