We are looking at buying a house where we'd want to build a single storey extension to the kitchen to form a large kitchen diner. The extension will have a vaulted ceiling - ie no roof space, but we want an island extractor fan in this space. Is it possible to fit an island extractor to a sloping ceiling? Or would I have to form a little platform to mount it to? Also, the ventilation - would it be possible to simply pass the duct through the roof to a vent tile? Or are these not suitable for this purpose?