I would like to change a cooker hood from recirculation to extraction to outside. The hood is mounted on an internal wall, however as the property is a bungalow it may be possible to run a rectangular duct in the attic and exit via a soffit.
The duct length would be about 3 metres. Is this practical?
I have looked at a Neff installation manual but it does not specify a maximum length. Just states the obvious that shorter, straighter and larger is better.