DIY Doctor UK DIY Forums

Hi, we had an extension built earlier this year. Per building regulations, we had extractor fans installed in each new bathroom, cloakroom and utility. Each extractor has its own electrical isolator switch and, to be honest, we usually leave them permanently off.

However, we have a problem with them. The external vent cover is quite flimsy plastic and rattles like mad at the slightest breeze. This is quite annoying since the house is otherwise quiet, especially the one in our ensuite bathroom. It also means that we routinely have a cold draft coming in to each room with an extractor.

(I'm quite surprised by this, since building regulations seem to be keen on making the house well insulated, then insist on putting 6in holes through the walls in most of the rooms. Add that to the trickle vents we now have on every double glazed window and it seems like a real retrograde step. But I digress.)

Anyway, I would like to put a stop to this rattling and also stop the constant drafts coming from them. We are unlikely to use them, but I don't necessarily want to permanently disable them. Can anyone suggest some good ideas to help with this?

I had thought of simply putting some tape over the vents on the outside, just to seal them shut. Since we have a pebbledash render on the walls, it seemed easier, and maybe more effective, than fitting a cowl like this:
However, while something like this will be quite easy on the downstairs vents, it will be a real problem upstairs since they are beyond the reach of my extension ladder (25ft+) and there are no nearby windows for easier access.

Do you think I could tape up the vents upstairs by taking the inside cover (including fan) off, reaching through and applying tape from the inside?

I had also wondered about taking the inside cover off and stuffing some spare Eco-wool insulation inside them to further block the drafts. Does this sound like a good idea?

Any critique on these ideas, or suggestions for simple, better alternatives would be most welcome!

The vents are there for a reason.

If you are not using the extractors in your home, you are heading for trouble.

Your bathrooms will start to get mouldy without them and damp will be a problem.

Turn them on and use them, it will save you money in the long run and you will soon get used to the sound.

Or get quitter units.

It is true the fans are there for good reason. With modern seals on widows and doors, lack of ventilation can be a problem in high humidity and odour areas. The fans are usually controlled manually, timed or by a humidistat. and really should be used.

Noise is often a problem unfortunately which is caused by the flaps that close the vent off when the fan is inactive. If this noise is annoying, the flaps can be replaced with ones that are electronically controlled. Although not the cheapest, will solve the problem. It is possible by changing the outside part of the fan for a downward pointing type, protection from the wind may be increased, hence less noise.

Hi Theo
Firstly as mentioned above, fans in any wet or humid area of a room are an absolute must and the fact you have turned them all off means any moisture that is produced in those areas is simply soaking into the fabric of the rooms and it eventually will become damp.
If you cannot replace the fans for a "auto shutter" type the the only cheaper option would be to change the outlets.
The type of Outlet you require is called a "cowled" outlet which is a grille that has blades or flaps on the face of it but has a sloping cover to protect it from the wind.
Also you mentioned 6 inch holes, you only need 4 inch fans in bathrooms and 6 inch in kitchens and utility rooms due to the litres a second air change rate they provide.
Also with a 15-20 minutes run on timer is the rule unless there is an opening window in which case a standard fan will meet the regs.
Domus ventilation do a full range I think available from merchants in the UK

Hi Theo

If you can get the fan out of the wall that is too high to reach from the outside you may be able to fit an internal "back draught damper" into the wall sleeve that connects the neck of the fan to the neck of the outlet.

This is a circular unit available in 100mm, 125mm and 150mm options and is a simple but effective way of stopping the wind from blowing back in through the fan when it is not running.
The unit is a circular piece of Upvc ducting fitted with a circular flap in the middle of it, this is pivoted slightly off centre which causes it to close when the fan is not running.
They are not air tight but will stop 95% of draughts coming through.
Just Google "Easipipe backdraught shutter" and you should find them
100mm is a "40494" 125mm is a "50594" and 150mm is a "694"

Hang on, what do you mean "never using the vents is heading for trouble"?

Have none of you people heard of windows? Windows are natural ventilation and have the added advantage of not using extra electricity. So far as I can tell, my 70 year old house has survived the first 69 years of its life without extractor vents, probably because its owners understood about windows. I am fully aware of the problems of humidity, I just don't need some idiotic and expensive ventilation system treating me like an idiot and making a noise in my ensuite bathroom, when it's right next to a perfectly serviceable window. If I wanted that, I'd live in a hotel.

At the very least we have trickle vents open in these rooms. Invariably we leave a transom window open for a few hours after a bath/shower. The gale that comes in (24 hours a day, 7 days a week) through the 6in hole in my wall due to the uselessness of the external covers is frankly TOO MUCH ventilation and - furthermore - is completely uncontrollable by me.

Also, you are missing the point of my question. I have not said the extractor fans themselves are especially noisy, just that the external covering vents rattle and are noisy.

It's a separate issue that we leave the family bathroom light on all night (with an energy efficient bulb, before anyone asks), so our young children can find the bathroom safely in the night, so I have no interest in leaving a fan on in there 12 hours a day. If I wanted the sound of an electric fan operating constantly, I'd have moved next door to a refrigerated warehouse, not next to woodland and countryside.

All I'm asking is whether there is a safe and simple method of stopping the cheap bits of plastic that pass for external covers on these things from rattling like a banshee whenever a squirrel farts in the woods to the side of my house.

I want a cheap, simple solution to deal with this nuisance, not a lecture on damp. Please? :?

(thanks for the helpful advice in your second post, thechard)

Building regs are there for a reason. Installers have no choice, we all have to follow them or we get into trouble.

The reason for the mandatory force air venting is a simple one, warm air and high levels of water vapour can cause mould spores and can cause breathing difficulties in confined spaces.

This does affect young children and there some research that it can be one of the causes of childhood asthma.

I do understand and see your point with windows but with people leading busy lives and concerns about home security, most people only have them open in the warm weather, not all year round


The solution is simple, if the noise of the vents flapping is keep you up, take them off and put up the draft and the rain getting in.

Or buy the better ones and have them fitted.

Peter the plumber said:
"This does affect young children and there some research that it can be one of the causes of childhood asthma."

According to research over recent years, childhood asthma is caused by too much ventilation, too little ventilation, too much cleaning/dusting and too little cleaning/dusting. I'd take all of it with a big pinch of salt. And I say this as someone who developed asthma as a child.

Presumably by having 6inch wide holes that cannot be properly shut in so many rooms of our house, making it draughty, we run the risk of childhood TB and rheumatism and constant chest infections?

Peter, you say that one would normally only open a window in warm weather. This is exactly my point, though. The nature of these extractors and the external vents is such that I effectively have a hole the size of a transom window open PERMANENTLY in several rooms of my house, since the extractors cannot properly be closed.

This makes the rooms uncomfortably cold during winter and has a knock on effect on the heating and ventilation in the rest of the house.

As an aside:
A relative of mine converted an old house into flats and put bathrooms in some basements. This room had the required plastic lining, with concrete shell inside, lined with plaster. For reasons too peculiar to go into, the owner of this flat refused to open her window, (there was no extractor fitted, since the conversion predated these being mandated) for SEVEN years, meaning that the room was basically sealed for that whole time. After that period the room DID become damp and the plaster developed mould.

I think this is the risk which extractor vents are designed to mitigate. I'm desperately trying not to use the phrase "nanny state" about this, but it's hard work.

Since no-one's said that you can't just tape the external vents shut, I'm going to give this a go. Depending on the effect this has on the draft, I may try putting some insulation inside the vent sleeve to help with this. Then I can happily use the windows for my ventilation, knowing that when I want a warm room, I can achieve it and when I want ventilation and air circulation it is completely within my control.

Again, Peter, You mention that better quality covers can be obtained. This certainly seems like a better alternative to having no cover at all, for reasons you state. I realise that the way these forums work seem to make it impossible to link me to other websites, or show pictures, but can you mention any specific products I could look for in this regard?

Well, that was the reply I got from the building inspector when I email him.

This site doesn’t like us to post links to “productsâ€

The vent is rattling because there is a difference in air pressure between the inside and outside of the house. The outside louvres act like an aircraft wing when air passes over them causing a depression, the higher inside pressure then forced the vent open.

Airflow make a fan (Icon 15/30 range) which has a diaphragm which closes off completely when switched off. This seals the outside to inside pressure and will vastly improve noise problems.

There is a simple way to stop extractor outlets (cowl) knocking/banging in the wind.

You will need 2 5mmx 1mm rare earth magnets, there is an example from eBay http://www.ebay.co.uk/itm/161598721229?_trksid=p2057872.m2749.l2649&var=460595392905&ssPageName=STRK%3AMEBIDX%3AIT

These magnets are incredibly strong for their size. They are dangerous if ingested or inhaled so make sure they are out of reach of children and pets.

I use an external monrose cowl vent http://www.screwfix.com/p/manrose-cowl-vent-white-125mm/54366

Your all need some good external grade glue, epoxy resin or something that will remain in place in low and high temperatures. Internal Super Glue will probably fail in winter temperatures.

Now look at the flap that closes, at the bottom is a square hollow indented part.



Glue the first magnet inside in the middle of the hollow section.

Now carefully glue the second magnet to the section of the cowl that you screw to the wall. Carefully aligning both magnets and ensuring you have the second magnet the right way round to attract the first magnet rather then repel. The Magnets should not touch or the attraction will be too strong for the flap to open when the extractor unit starts.

Tip: Attach the second magnet with see through tape until you have it aligned. Check the flap opens when you switch on the extractor hood! Once aligned, carefully and slowly peel back the tape until the magnet lifts off, apply glue and then reapply the tape until the glue is set.

Once complete the attraction between the magnets will hold the flap closed when the extractor is not in use. It's strong enough to hold during strong winds and keeps the hood airtight and best of all, stops the annoying knocking/banging.....

Obviously you can use this method with any external cowl with a flap. Magnets can be purchased cheaply in varying sizes and strengths. Good luck...

Hi rbetts100 can you say which glue you used to attach magnet to cowl frame, i used some superglue which lasted a week then magnet pulled off.

Yes super glue will fail due to movement during tempreture chnages. I used expoxy resin, one that was on for outdoor use.

rbetts100 many thanks will give it a try

I've mastered the FIX on rattly extractor fan vent! I'm living in total utopia PEACE AND QUIET RULES ONCE AGAIN!

Right.....the fix, you just need a weak spring and a hot pin.
Remove the cover plate and flap...and heat a pin on the hob and push through the casing and the flap...now thread through the tips of the spring and bend over to prevent it from coming out again...reassemble and hey presto....SILENCE! And when extractor is on it overcomes the spring and works a treat!
(Picture attached)

Thank me later guys! Your welcome....enjoy your sleep!