Extractor hood ducting through flat(ish) roof

[iep]

I need to run a cooker hood extraction vent through a flatish (6 degree) roof. I've been on the Klober site and all the roof vents they show seem to be for roof space ventilation rather than mechanical extraction from a cooker hood or similar.

Roof is single ply rubber and the guy who installed it is lined up to fit whatever vent I want to buy so no worries there. I just don't know what type of vent I need or where to buy it. Can anyone suggest a suitable product?

Also, I'm guessing that I'll need to use metal ducting since the extracor will be above the cooker?

Cheers,

iep

 

[OwainDIYer]

usually for domestic work 100mm soil pipe is used, treat as a soil vent pipe through the roof, and fit a 'mushroom' cowl on top of the pipe.

 

[iep]

Thanks, I think I'll need a 125mm pipe as that is the output diameter on the cooker hood (instructions state narrower diameter pipe will cause issues).

Sounds like a basic plastic pipe with a mushroom cowl is an acceptable solution though?

Cheers,

iep

 

[iep]

My roofer is also saying that a 100mm soil pipe is normal for extractor hoods. I don't mean to doubt but is seems odd to reduce the pipe diameter from the output of the extractor fan.

That said, if 100mm is used everywhere then I guess it works fine for most applications?

Cheers,

iep

 

[JohnD]

a 125mm fan is a bit quieter than a 100mm fan for the same throughput.

It sounds as if your hood is directly under the flat roof and has a very short vertical duct. this is really ideal for extraction so I think you will get a good flow of air even if you reduce to 100mm

You might be able to find a 150mm mushroom if you want it, but unless you have a commercial kitchen 100mm is quite normal.