Non return extractor fan solution

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Hi,

During the construction of my extension, i specified that I wanted a ceiling extractor fan, whilst this sounded like a good idea at the time, I am starting to have second thoughts ? You may ask why ?

Everytime the extractor fan lets in cold air even when its not on, what I expected was that it would only let air in when its on, I looked into a non return valve, however as this is roof mounted, its not going to work well because of gravity, the non-return valve types works on wall mounted extractor fans.

Does anyone have any idea as to what i can do ?

Thanks in advance

This is the extractor from the ceiling.

WhatsApp Image 2021-12-27 at 22.37.19 (1).jpeg


On the roof outside, tried to use a material to block it in, its falling apart and i need a better solution.

WhatsApp Image 2021-12-27 at 22.37.19.jpeg
 
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you can get a non-return flap to fit to the duct.

they are usually designed to work on a horizonal duct so the flap swings shut under gravity. I expect it would work vertically if the fan was fairly powerful.
BackdraughtStandard.jpg

but there are now butterfly valves with practically no weight. They will open if you blow on them.

Like this
backdraughtButterfly.jpg

Some of the better extract fans have them fitted as standard (e.g. the Soler & Palau Silent 100, also branded Envirovent), but you can also buy them as an accessory. I will see if I can find one to see the brand. I think I had some that were made in Eastern Europe.

Is your duct 100mm?

You will probably have to get your stepladder out and take the fan off the ceiling so you can fit the non-return.

Do you know the make and model of your fan?
 
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Thanks JohnD, the fan is a Blauberg 150mm Timer fan, from what I remember it was stepped from 150mm - 125 - 100m for the pipe on the roof or from 150 dow to 100mm, I will remove it to find out. As I do not want to cut the pipe from the roof, I will have to do it all internally, I will take the fan out and measure the diameter again.
 
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this looks like the ones I had

If it's the same, the rim push-fits into the duct but you may need to check the precise measurements, or you may end up sealing it with duct tape.
 
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I will remove the fan completely to work out what I need. Thanks very much once more.
 
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I have a butterfly valve fitted vertically and upon testing, had little effect on the performance of the extractor
 
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Why not fit a fan that remains on trickle when not fully on. My bathroom extractor has a trickle fan setting so is permanently venting and when the light is operated the fan kicks in fully. We don't get a draught at all.
 
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My downstairs loo suffered a bit of a breeze.
The ceiling fan formed a U and vented into the soffit.
I didn’t allow for the hot air rising and flowing through.

after a cereal box first go, I fired a purpose made “lid” that helps prevent draughty air movement
It looks a little like this
https://www.toolstation.com/xpelair...ontour-extractor-fan/p24440?bvstate=pg:2/ct:r
but has sides so the air has to be sucked up and around to leave the loo.
I can’t find the one I fitted
 
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Fit a back draught shutter, or a fan with one built in.

A better option would have been a fan with constant trickle extract, and boost when needed.

It's unusual for this type of installation to cause air input when the fan is off. Normally this is indicative of lack of ventilation elsewhere in the properly, which causes air to be drawn in not kept out from higher pressure.
 

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