Hello, I thought i'd fit the extractor fan we bought last year as part of a new kitchen, so it's now finally attached to the wall. Naturally I cannot use the vent hole i made for the previous one (i'm only about an inch and a half out though, bastard!), so a new hole is going to be necessary.
The extractor wants 125mm duct, I thought i'd be OK because I have a
127mm core bit but no, I need nearer 130 so must be i/d.
So shall I reduce down to 120mm? Depending what I read it would appear 125mm has up to 50% more airflow than 100 but along a run of about 1/2 metre is this realistic? I might buy a larger core and stick to 5 inch.
And i'm compelled to use rigid pipe instead of that nasty flexible s**te, opinions?