We've just fitted two new extractor fans and a new cooker hood in our new house. Trying in advance to prevent banging and rattling, I installed cowled covers on the outside, but they are still banging so much - and not just when its really windy. We live in a rural location and the vents are all on the side of the house that is a the top of a hill, so it's as if the wind is just blowing up the cowels and opening the covers. The banging is pretty much constant as there always seems to be a bit of breeze here. Its infuriating! Any ideas for other options that would work? I don't have a loft as its converted so can't vent them through there (and two are on the ground floor anyway), and I'd rather not replace the fans now as they have only just been fitted and we're expensive 'silent' ones (the irony!) plus we've just spent a fortune decorating so really trying not to have to make any mess inside now. So I know I could replace the bathroom ones with new fans with electronically controlled vents but that would be the last resort. Are there other options for external covers that are going to be more effective in the situation than the ones we have - would inline backdraught flaps be better maybe? Or is there a brand of covers that is just heavier with stronger springs and better quality than the ones I've bought (they are manrose like these ones www.screwfix.com/p/manrose-cowl-vent-white-125mm/54366 - they have flaps inside the cowel which you can't see in the photo). Please help, i'm going crazy with the noise!