Flapping Ventillation Grille

[happyolly]

I've moved to a new build on a very windy site.
The extractor fans in the bathrooms are always on and boost when humidity gets high or the lights are turned on
There are further fans in the utility and kitchen that are either off or (very) on. The utility one I'm unlikely to ever use.
There are external louvred/flapped grilles on the exterior that are exceptionally noisy and rattle and flap in the wind.
If I remove the louvre completely then the pressure the fan in trickle mode does not overcome the gusts of window going the other way into the house so it seems I can't avoid some form of draught flap.

So....getting to the point....what's the quietest method or am I on a hiding to nothing as the continuous trickle will always hold open any draught flap such that it will be caught by the wind?

Maybe something like this?

and then something like this on the outside

 

[John D v2.0]

Yes those internal flaps are much better and can't be caught directly by the wind. The cowl might help depending on the wind direction.

 

[stem]

Much of the rattle is cased by air entering another part of the building and escaping via the vent causing it to flap. In this case, all gravity / air operated shutters will rattle. The only permanent solution is to fit a fan with mechanically or electrically operated shutters that only open when the fan is switched on.

Something like this:



Not sure if you can get a trickle fan version though.

 

[happyolly]

Much of the rattle is cased by air entering another part of the building and escaping via the vent causing it to flap. In this case, all gravity / air operated shutters will rattle. The only permanent solution is to fit a fan with mechanically or electrically operated shutters that only open when the fan is switched on.

...that's not the cause here though - the rattle is caused by wind outside. 3 of the 5 fans are permanently on in trickle mode which is not strong enough to overcome incoming gusts.

 

[John D v2.0]

Much of the rattle is cased by air entering another part of the building and escaping via the vent causing it to flap.

Did not realise that, but it makes sense! We don't have flaps on ours but ours are also on constant trickle. Perhaps the op can just remove from the trickle fans completely.

 

[stem]

Generally with the trickle fans, the trickle keeps the flap open slightly and then when the wind blows it slams shut causing the noise. The air leaving generally is more of a problem with traditional fans when they are switched off.

Most of the complaints I get are because of the noise a bathroom fan shutter makes during the night when off. In this case the flaps are closed and the air leaving pushes them open and then they flap back in to place. With a constant trickle fan it would be less likely as the trickle of air would stop them closing completely.

 

[happyolly]

With a constant trickle fan it would be less likely as the trickle of air would stop them closing completely.

The volume of air going out on trickle mode is nowhere near enough to counteract a strong gust of wind pressing on the louvres. In fact I think it makes flapping worse as it gives the wind more of a gap to get under to lift the vents up.

 

[stem]

Indeed! Like I said.

Generally with the trickle fans, the trickle keeps the flap open slightly and then when the wind blows it slams shut causing the noise.

The process is slightly different with traditional fans, there is no permanent air leaving that will keep the flaps slightly open, so air leaving from inside the building opens them and gravity causes them to close. They will flap even with light winds, this is not usually the case with a trickle fan which will keep them open unless the wind is quite strong.

 

[happyolly]

...umm....so what do I do no louvres?

 

[John D v2.0]

Those icon fans in stems 2.00pm post are a good solution

 

[stem]

I think it will be drafty if you do that, but you may be able to carefully remove the flaps from one of the fans and try it for a while. As far as I can see it's either a matter of getting used to it, or replacing the fans for something with positive action shutters.

At my last property, I installed a loft mounted central fan which was housed in a box having a duct to each of the rooms requiring extraction. The outlet, without any shutters was then mounted horizontally on the soffit facing downwards and not facing the wind. I fitted two separate speed controllers, one that was manually adjustable to boost the system as and when required, and the other was linked to a PIR in a central hall that ran it in trickle mode for two hours once triggered. I later upgraded it to have a second fan and heat exchanger for heat recovery. Didn't get any discernible drafts from any of the outlets.

 

[happyolly]

I've removed the external flaps/louvres from the ensuite bathroom vent as it was impossible to sleep in the main bedroom.
Getting used to the noise just isn't an option.
Possibly an internal flap arrangement like I posted the picture of above would be quieter - I will probably buy one and give it a whirl.

"Positive action shutters" I guess don't really solve any draught issue when we're talking about trickle fans as they would always be open.

 

[stem]

"Positive action shutters" I guess don't really solve any draught issue when we're talking about trickle fans as they would always be open.

The idea behind:

replacing the fans for something with positive action shutters.

Was to replace them with fans that don't have a trickle facility.

 

[happyolly]

For sale: 1 month old extraction fans, 5 available

 

[stem]

Just a thought. As it's a new build, is it part of a development? If so, how about contacting it the developer and adding it to your snagging list to see what they come up with. I assume that your your neighbours will be having the same problem perhaps you could encourage them to do do the same.

Even if it's not part of a development you could speak to the builder.