Ducting extractor hood with 150mm outlet - 220 x 90 mm flat duct through cavity wall?

[andreas]

The extractor fan I have to fit has a 150mm spigot and advises that you must not reduce to 125mm, but you can adapt to 220 x 90mm flat. I don't quite have room to run 150 round ducting, but I could relatively easily run a 220 x 90 flat duct directly through the wall. Is there any issue doing so? The only obstacle I've found so far is that I cannot find any form of external wall vent termination with backdraft flaps for that size flat ducting. I have found a 220 x 90 joiner with damper fitted internally, that would have to be placed in the hole cut in the internal leaf of the wall, then a (very) short bit of duct to the back of a standard double vent airbrick. Any issues with doing that as well?

Any other suggestions?!

[Nickfromwales]

46 minutes ago, andreas said:

The extractor fan I have to fit has a 150mm spigot and advises that you must not reduce to 125mm, but you can adapt to 220 x 90mm flat. I don't quite have room to run 150 round ducting, but I could relatively easily run a 220 x 90 flat duct directly through the wall. Is there any issue doing so? The only obstacle I've found so far is that I cannot find any form of external wall vent termination with backdraft flaps for that size flat ducting. I have found a 220 x 90 joiner with damper fitted internally, that would have to be placed in the hole cut in the internal leaf of the wall, then a (very) short bit of duct to the back of a standard double vent airbrick. Any issues with doing that as well?

Any other suggestions?!

That solution is fine, and as long as the joints are glued or taped you’ll not have any issues there.

 

I removed your duplicate post btw   

[andreas]

59 minutes ago, Nickfromwales said:

That solution is fine, and as long as the joints are glued or taped you’ll not have any issues there.

 

I removed your duplicate post btw   

Thanks Nick, on both counts