Ducting size for kitchen extractor

[TKH]

I have made a big kitchen dining living room with gas hob. The room measures around 60 to 70 square metres. I found a few websites that all recommend an extractor that can flow up to 10 times the rooms volume. This bit is not an issue but I have to duct the exhaust about 6 metres through the ceiling joists. It would have a 90 degree shoulder then go straight. What size and sort of ducting would you use? I read that over 6 metres I would get about a 5% drop in flow if I use 150mm solid pipe. I guess that should be ok with out an extra inline fan as we are talking such a beefy extractor anyhow. Any advice is most appreciated

 

[jj4091]

Are you sure it is safe to put ducting that size through ceiling joists, you would severely weaken joists by putting holes that size through them.

 

[motorbiking]

The other option is to mount an extractor on the outside wall away from the hob. there are plenty of 5" fans capable of 70l/s or more.

 

[chappers]

that's what I would do ^^^^