Extract fans that lift air.

[Paul Drawmer]

I'm planning on puttinga kitchen extract in the roof of our two story house. It will extract through an exiting roof vent.

How do I size a fan that has to lift the air 9m? Presumably there's some 'chimney' effect once the column of air is moving?

I'm fitting a 150mm duct up from the hob hood into the ceiling void, where I want the fan mounted. The plan is to have an effective vent without the fan noise in my ear whilst I'm cooking.

[Paul Drawmer]

rossjohnstone said:

To work out the duty of the fan you'll need to know the volume of air that youre trying to move, what are the dimensions of the room?

Room volume is only 30 cubic meters.
It's the steam that's a problem, so I've already allowed for a condensation trap/run off.

[Paul Drawmer]

So..never having had an external cooker extract before, do domestic installations require regular duct cleaning?

My fan in roof plan was to move the noise source as far away as possible. It sounds as if it is going to be a 'must' to use rigid ducting, and to allow for access to clean it when the grot takes over.

Ok on the calcs - I'll be studying the specs of the filter manufacturers now.