Fan In Flat Warm Roof

securespark

securespark

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At the suggestion of our reputable builder, we had a fan fitted over the shower in the ensuite. The previous effort through the wall was pathetic, causing condensation and damp hence wanting something more efficient.

The alternative was to run a duct from the flat roof into the main loft into an inline fan, then out through a gable end wall. This would have been my preference, but the guy from the building co. was adamant his flat roof idea was fine and met building regs and didn't need any paperwork from building control.

I can't take any pictures of the external set up, but I'm not sure they used a proper flat roof vent kit.

Trouble is, the fan is constantly "hunting". It always seems to be changing speed and even when off is often spinning, so it is obviously affected by the wind.

Is this a bodge job? Does it need paperwork from Building Control? Do I need to call them back?
 
Xpelair Simply Silent.

www.toolstation.com

Xpelair Simply Silent DX150R 150mm Round Extractor Fan

Noisy bathroom fan keeping you awake at night? Switch to Simply Silent from Xpelair - this 150mm round extractor fan has two speed settings, allowing you to choose between increased airflow or near-silent operation.The two modes offer extraction rates of 214m³ or 241m³ per hour with noise levels...
www.toolstation.com www.toolstation.com

It's supposed to be quiet, but to my mind, it's bloody noisy. I don't have a decibel meter to check it, though.
 
The fan you have does have a back draught shutter but any slight stress caused when fixing to ceiling or connecting the ducting can prevent this from working correctly.
The DX150R is not the best choice in this instance for many reasons.
For a bathroom/shower you would be better having one with a timer or humidistat function.
Would also be better with a LV option if in shower area unless you only have a fixed head shower.
 
Is there a way to fit a better more reliable one?

On the roof end of the duct?
 
Feck said:
The fan you have does have a back draught shutter but any slight stress caused when fixing to ceiling or connecting the ducting can prevent this from working correctly.
The DX150R is not the best choice in this instance for many reasons.
For a bathroom/shower you would be better having one with a timer or humidistat function.
Would also be better with a LV option if in shower area unless you only have a fixed head shower.
Click to expand...
Thanks.
What is the job of the back draught shutter?
I guess it's only to stop wind getting in when the fan is at rest?

For some reason, the box said it was the R model, but it does have a timer. And it is outside the zones and on an RCD protected circuit.

Like I said to Fox, I need a way to stop wind getting in when the fan is not running, but what will stop the wind interfering with the rotation of the fan when it is?

Is there something wrong with the fan?

Thanks again.
 
securespark said:
What is the job of the back draught shutter?
Click to expand...

They are a sort of one-way valve - they open when the extracted air is blown at them, then close, to prevent cold air entering. The gravity type, must be mounted in the correct orientation. Some use powered shutters, either solenoid driven, or heated wax capsule.

My wall fan has a gravity type, on the outside, and a wax capsule operated shutter on the inside, like a camera shutter mechanism. The fan speed and noise, will vary, when the wind gusts, due to variations in air pressure. Nowt much can be done about that.
 
Just got a decibel meter on my phone.

Propping the phone on top of the fixed shower head near the fan, maximum background noise inside the ensuite with the window on trickle vent is 35.

After switching the fan on, maximum is 76.

I couldn't catch the hunting noise this time, nor the noise change where it goes from very noisy to very quiet, then back again, but I did catch this odd start up noise, as if the motor is struggling.

The sever says the file is too large and I'm not sure how else to upload it.

View attachment 373021
 
A vent in a roof is prone to the chimney effect, where warm or humid air will naturally rise out even when the fan is not running. In some cases this can be utilised to ventilate a steamy bathroom without using a fan. But a hit and miss or other control is useful to prevent the room getting too cold in winter. Very handy in sports changing room showers and washrooms that may not be regularly heated so are prone to damp, and the users are gnarled and hardy.

I don't understand the excessive noise, but the free airflow and the effects of wind gusts explain the hunting.

A fan with an iris or shutter that snaps open or closed electrically should fix it. Or it might be possible to have a flap that will be held shut by gravity until the fan is running fast enough to lift it. A cowl vent on its side has this. Annoyingly there will be extra expense.

I can't think of an easy solution as you may need roof access to try a fix.

The quiet fans I use now have a "butterfly" backdraught shutter, hinged in the middle and very thin and light so they only need a whisper of air to open.

Does yours have a mushroom-like roof vent?
 
Well, the replacement Xpelair fan is on its last legs now. It's noisy AF and the impeller is spinning unevenly.

As far as I can see, I have three choices in order of price, cheapest first:

1. Replace it with another similar ceiling mounted unit. I can only find two other round ceiling mounted units:

Europlast 150mm (30-odd quid) or Icon 60 with timer module (130 quid).

2. Fit an in-line fan in the loft. This will entail pulling down plasterboard in our fairly recently renovated bedroom, and going up in the loft where we have had new loft insulation laid.

3. Fit an on-roof fan, such as Vent Axia TX6RF. They are £450ish.

Any advice?
 
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