Allowed to share extraction fan ducting?

[ashthekid]

Hi,

 

This may seem like a silly question but is it allowed by building regulation/control to have multiple extraction fans share ducting to one exterior outlet?

Is yes is there a limit on how many are allowed?

I have a couple of rooms with no windows or natural ventilation that I'm assuming will have to have some sort of extraction but to keep things simple and not have excessive ducting all over the place I thought it sensible to have, for example, the TV room, utility room, pantry and toilet all extract to one outlet. Of course it may seem risky to have a toilet connected to the same ducting as the TV room in case of smells passing through?!?

 

I just wasn't sure of the building regulation for this topic.

[ProDave]

No.  "use" the toilet and it's fan comes on, the other rooms are likely to get smelly.

[JohnMo]

MEV allows multiple extracts to a single outlet.  In that case you ventilate the wet rooms and possibly the ones with no other ventilation.  The inlet flow would then come window trickle vents and cross flow through the house.

 

Or go dMEV, these have a fan in each wet room and have always running, low energy fans, with boost from light switch or humidity sensor.  Put through wall vents (on internal walls) in the unventilated rooms. For this to work you need an air gap at the bottom of all internal doors.  You window trickle vents work as MEV.

 

Best to draw your house layout, look at where to have air going out already, where you have air coming in (window vents etc) and then can make a guess at where the air flow to and from, and see what room have no ventilation.  Ventilation wants to go across a room where possible.

[ashthekid]

Does it matter if it's a conversion project (and change of use from commercial to residential) and not a new build with regards to the build reg expectations?

[ashthekid]

Here is the floorplan for the ground floor.

I've marked in red the only windows we have with trickle vents.

To the south there is the directly connected neighbour so no chance of any wall outlets and to the north is the neighbours garden and the solid wall from the pantry all the way to the west is an old chalk cob wall that will be impossible to have an outlet. The only place possible for an outlet is the north wall between cloakroom and boiler room.

And because we are in a conservation area I cannot just have loads of modern outlets.

[ashthekid]

Any more thoughts on this?

[PeterW]

Go out through the roof…? MVHR would be your friend here as you can put multiple extract points on a single plenum and fan unit.
 

Was this not planned into BRegs submission ..?

[Dave Jones]

a cheaper version of mvhr is the vent axia multivent. Can pull from 3/4 rooms and dump via wall/ceiling vent. approved for building control and only a few hundred quid.

 

https://www.vent-axia.com/range/lo-carbon-sentinel-multivent-plus

 

 

[ashthekid]

Yes MVHR would be ideal if it wasn't so expensive. I had already briefly looked into it and no company would do a small section MVHR setup, only whole house and that was running into the thousands then. Sadly I can't afford that.

 

I can't go through the roof with any new outlets but can certainly try and merge ducts into existing roof outlets. If that's allowed by building reg standards.