Christian McArdle wrote:
We're having our kitchen extended and the architect has noted (on our
building plans) that we need an air extraction rate of 60 l/min.
Question: Can this all be catered for just using a cooker hood
(extraction to the outside), or does it need a 'higher up' fan?

Be careful if you are using any length of ducting. Any significant
length will annihilate the extraction rate, especially if it is an
axial fan, rather than centrifugal. If it is straight through an
external wall, then there is no problem.

Thanks.
It'll be a twin centrifugal fan unit, and straight through to the outside.