This is what an extractor fan louvre should look like when in operation. I am not sure that I have ever seen this in practice. Wracked my brains, but apart from louvres on commercial systems I cannot recollect ever seeing much more than an occasional feeble movement. Certainly on my home there is rarely more than a flutter.
So if the louvres aren’t moving, then the fan is not working properly, but this is the situation with virtually all extractors in the UK. So this in turn means that we are not dealing with ventilation as we should. All the calculations in Part F of the building regs etc are just a waste of time if the equipment we use is just rubbish.
The real life situation is made worse of course if the vents are facing the prevailing winds. With such minor pressure coming from the fans any extracting doesn’t stand a chance against any sort of wind. Then we also fit any draught devices that just make it even more difficult for a poor fan to extract the volume of air required to keep condensation down to acceptable levels.
So what to do?
Well, it is worth having a look at a video from Envirovent. https://youtu.be/k5rlDfWPAgw. This helps to show the effectiveness of different types of fan on the market.
This video looks at standard type fans, but you could also look at a dMEV fans. dMEV are Decentralised Mechanical Extract Vents. These work by continuously extracting air from a localised position (like in a bathroom). There are various manufacturers and types. So you can have more sophisticated ones that work by sensing factors like humidity, so as humidity increases, so the fan will respond according by extracting more air. They can also be controlled by timers & pull switches and combinations thereof.
So, if you have mould etc in your kitchen / bathroom, despite having an extractor fitted, almost guaranteed it would have been the £10 model from the local electrical factors or DIY store. So I would recommend that you look to replace it with a good quality fan that actually works rather than just making some noise.
I will be replacing mine at home very soon. I will have a standard fan in the upstairs bathroom (as this is an ensuite and also made of breathable materials) and a dMEV in the downstairs bathroom that can run continuously. The downstairs room is more prone to mould as it is less well insulated and more heavily used, hence the decision. I will be changing the one upstairs myself as it is a simple case of changing leads over from one unit to the other, but the downstairs one is currently operated by the light switch and so we will need to get a continuous live feed into this. Probably a simple job, but not being a ‘sparky’, I would prefer the confidence that a professional brings to the task.
So, as ever, it seems like you get what you pay for. So as a special note for people living in older properties. We have spent much of the past decade sealing up houses in the name of energy efficiency and carbon savings. This has meant that many of the sources of fresh air have gone and we are living more and more in warm, humid and still environments. This is not good for your health or for the health of the building. We need ventilation. We need fresh air. We need to remove warm moist air in order to reduce the risk of mould growth. So look to get a good working ventilation system in place at home. This starts with mechanical extract from high risk zones like bathrooms, toilets. kitchens and utility rooms.
Get good fans that actually work.