New extractor fan makes a banging/popping sound when it's windy

[minipie]

So we recently had a new bathroom extractor fan fittedthis one. It's on an external wall and is vented straight through the wall to the outside. It seems to do a decent job and is quiet when it's on.

However when it's off, and the weather is windy, it is making a banging sound - it sounds as if some internal part is being banged back and forth so there is a loud "pop" every couple of minutes or so. Very annoying especially at night!

From a look at the technical spec it looks like there is something called a "backdraught flap" deep within the fan body, so I guess it might be that which is banging.

Has anyone had this problem and managed to fix it somehow? Pigletjohn do you have any ideas please...? Ironically we chose this model because it is quiet the old one was noisy when running but didn't make this banging sound.

where the vent exits the house is there a cowl or vent?

can you recognise it here?

It is more often that outside one that blows about.

The picture is not clear but it looks like the flap is like a butterfly's wings. I might try rotating it by 90 degrees.

Thanks PigletJohn. I don't actually know what's on the outside, will take a look tonight. Yes rotating is a good idea - that wall is actually quite protected (as it's very close to the next door house) so suspect the particular angle could have quite a big effect. Thanks.

If there is no cowl, would it help to have one fitted (big pain as really needs scaffolding to get up there safely...)

Oh, I have also read suggestions to put gaffer tape or rubber draught sealing strip along the flap edge so it doesn't bang so loudly. But that would risk the flap sticking, right?

thanks again!

EDPM draft strip where the flap closes will cut the noise, but leave it prone to draughts.

I prefer a cowl vent, the shape discourages wind and it just has one big flap inside. The ones with little venetian blinds are very bad for rattles.

This definitely sounds like it's just one big thing "popping" or banging rather than lots of little bits rattling ... will try to get a good look at the outside tomorrow when it's light! Next step will be to dismantle from the inside and see what we can access without having to go from the outside. Thanks again PigletJohn.

A local roofer might be willing to do it off a ladder.

I have wondered about this - when the wind blows in a certain direction it sounds as if it is rattling sheets of corrugated iron inside the roof of our loft conversion, and I think it is getting in through the bathroom fan.

this sort stop rattling when the flaps fall off in a strong wind

this sort rattles less