DIY Doctor UK DIY Forums

Been given a Hygena cooker hood model APP2400. External diameter on top of the hood is 6 inches [see picture}]

The white plastic bit is the one way valve/flap. It sits in a metal collar that is part of the fan unit below. Apart from a gravity flap on the outside wall, any other considerations to bear in mind? Does it matter if we use flat or round trunking? Flat would make for a neater job. I'm guessing the joints are sealed with either mastic + tape or a solvent?[img]http://img101.imageshack.us/img101/347/cookerhood.jpg[/img]

Your main consideration is to keep the diameter of the trunking as large as possible. Flat trunking is neater and can be used if the run is short, but it does restrict the flow to a noticeable degree.

If the extractor has an internal flap, don't fit one on the outside wall as they flap about even in a small wind and make a terrible racket!