4" into 2" doesn't go - extractor fan ducting

Ken mare

I've an ensuite in the middle of the house, no external walls or windows adjacent, mould issue despite all attempts to eradicate. There is a void space over the ensuite where the extractor fan is fitted and after upgrading to a more powerful model I noticed only a small improvement. Re-investigated and discovered that the 4" extractor pipe joins a 2" pipe which runs to the attic. There is another floor above the ensuite so do I bite the bullet and channel a 4" pipe through the floor and room above and box it in or is there a fan that I can put in the attic to sort the issue?
All suggestions and tips gratefully appreciated

listermint

1- is the existing pipe well secured and well fitted. i.e all the fittings sealed together properly with ducting tape ?
2- does the bathroom door have adequate ventilation under the door itself to allow negative pressure. This is a requirement for the Fan to operate effectively at all. Often forgotten about as people want as minimum as a gap they can get between door and saddle board

Ken mare

Pipes were connected with masking tape, can't understand how the engineer signed off on it and the builder has since gone bust.
The gap under the door is a very interesting point and I might get the door shortened or run the fan with the door open prior to using the shower with the door closed.

listermint

Ken mare wrote: »

Pipes were connected with masking tape, can't understand how the engineer signed off on it and the builder has since gone bust.
The gap under the door is a very interesting point and I might get the door shortened or run the fan with the door open prior to using the shower with the door closed.

Get the tape changed first. And get the door planed at the bottom. You need a gap usually in the 10mm range

Kevin Finnerty

I had something similar with a kitchen hood extractor fan, where my ducting was solid 4 inch all the way. Sort out the binding issues with ducting tape and tie wraps first and look for inline fans if you're having no joy.

Outkast_IRE

Also what paint is used in the bathroom , any internal en-suite would want the proper spec bathroom paints, if the area is prepped correctly and the paint applied correctly i have never seen them go mouldy.



Ventilation is key though i would be sorting both out. Also the pressure the fan can generate will be dissapated too quickly in a 2 inch duct, its a non runner completely , puting an inline fan is not the best solution but may work as they generate a much higher pressure than the ceiling mounted ones. I would reccomend going to a 4 inch insulated duct, you can go flexi if you want but the pressure drop in flexi is higher per metre than solid duct.

Ken mare

Thanks for the help, greatly appreciated!
I used bathroom spec paint on the walls and Bin Anti Mould on the ceilings. The mould appears on the tiles though almost for spite.
I feel that the 4 into 2 equation is killing me here to be honest and will cost having the run opened to include a four inch pipe to the attic, will be a bit messy but once boxed off should be worth it in the long term. 4 in insulated duct seems the best option and will give the fan a proper chance to vent.
The door ventilation issue is something I would never have thought of, it does make so much sense though!

Outkast_IRE

Ken mare wrote: »

Thanks for the help, greatly appreciated!
I used bathroom spec paint on the walls and Bin Anti Mould on the ceilings. The mould appears on the tiles though almost for spite.
I feel that the 4 into 2 equation is killing me here to be honest and will cost having the run opened to include a four inch pipe to the attic, will be a bit messy but once boxed off should be worth it in the long term. 4 in insulated duct seems the best option and will give the fan a proper chance to vent.
The door ventilation issue is something I would never have thought of, it does make so much sense though!

One last question is there a run on timer on the fan or is linked to the light ? It should run for another 15 mins after the shower

monseiur

When installing your 100 flexible duct - to avoid joints feed the duct down from the attic thru the room above to bathroom. For a neat job cut opes with a 110mm core saw. In attic run duct vertically to external vent on roof, strapping it on to nearest rafter, collar tie etc. you may have to install extra timber support depending on you attic lay out.
How is you existing 2'' duct connected to external vent ? If the vent is 2'' you will have to change it to 4'' or you could divert the duct to the nearest soffit - there are duct termination kits available for this.
M.

Ken mare

Laid low with a virus at moment so haven't been able to further investigate.
From the great tips my plan is to trace the 2in pipe to the attic, there is an outlet on the roof tiles so I'm hoping that by replacing the internal 2in pipe with a 4in one I can run it straight to the roof tile vent.
Going to change extractor to timed one also.

jhenno78

If I'm reading this right, the problem is that you have a ground floor en-suite that runs up the middle of a 1st floor stud wall into the attic and out?

So...problem 1 is that there isn't enough room in the wall to run a 100mm pipe? and your solution is to run a vent pipe up through a room to the attic and box it in?

Would it be possible instead to use flat-profile ducting (eg. 203*60) up through the existing wall?

Isn't there an inherent problem that you're going to get a lot of condensation in the vertical stack?(insulated pipe or not)
Is it possible at all to route it out level between the joists?