Bathroom Fan Extraction Advice

[BathDIY]

My bathroom is 9.936 m^3.

We are seeing issues in the loft with condensation, my understanding is I need better fan that extracts as follows:
99.36 m^3/hr.
28 Lt/sec

However given the loft condensation issues I am seeing above the bathroom, would you recommend an uplift?

 

[flameport]

You need to stop air entering the loft from the bathroom and the rest of the house - any holes around light fittings, loft hatch or anywhere else must be sealed.
The loft may need extra ventilation via soffit or ridge vents.

Bathroom extraction is unrelated.

 

[conny]

If the fan is venting into the loft you need to fit ducting from the fan and terminate it at an outside wall, so all moist air is expelled to the outside.

Can you post pictures of the current set up?

 

[BathDIY]

You need to stop air entering the loft from the bathroom and the rest of the house - any holes around light fittings, loft hatch or anywhere else must be sealed.
The loft may need extra ventilation via soffit or ridge vents.

Bathroom extraction is unrelated.

Thanks, @flameport I have continuous soffit vents and some roof tile vents (also sealed loft and insulated as far as poss). May need more vents through. Have also already worked to plug holes in the ceiling from old boiler pipes / light fittings etc.

If the fan is venting into the loft you need to fit ducting from the fan and terminate it at an outside wall, so all moist air is expelled to the outside.

Can you post pictures of the current set up?

Thanks @conny The fan is vented through a roof tile vent, am assuming I should periodically remove ducting and clean it?

You can see dampness on the plywood (used to support the valley) in the bottom right of the image. Obviously, plywood is so thin it condenses at this point rather than the rest of the roof. It is far worse here than in the other valley today when I go up this is the only visible damp patch.

 

[JohnD]

Do you have holes in the ceiling, for example for downlights or pipes?

How long does the fan run on for after you turn off the bathroom light?

Do you have steamy showers? 100 cu.m/hr will not be enough

How often is the fan turned on?

Your existing fan looks reasonable. Do you know what model it is?

Verify with a smoking joss stick that it is sucking well from the bathroom, and not leaking into the loft, for example if the duct is torn, or blocked with a birds nest.

 

[BathDIY]

Do you have holes in the ceiling, for example for downlights or pipes?

How long does the fan run on for after you turn off the bathroom light?

Do you have steamy showers? 100 cu.m/hr will not be enough

How often is the fan turned on?

Your existing fan looks reasonable. Do you know what model it is?

Verify with a smoking joss stick that it is sucking well from the bathroom, and not leaking into the loft, for example if the duct is torn, or blocked with a birds nest.

Thanks, @JohnD have downlights in the downstairs kitchen but nowhere else, thinking of dropping ceiling and adding more, perhaps I should reconsider this?

The fan goes on with light runs for the max setting (a couple of minutes) I leave the light on till the tiles are dry (wipe down shower area and window after use).

Yes my wife and daughters have steamy showers, (I do what I can to limit this) I have checked out the code on the label and it seems to be an NL8001 so 52l/s at slow speed (245m3/hr)

Will buy and check with a jostick when I can buy one.

It seems to suck up loose kitchen paper (if that makes sense so doesn't seem to be blocked). Cannot see birds nest or blockage from outside.

 

[JohnD]

The power of your existing fan should be adequate. Run on timers can usually be adjusted to 20-30 minutes.

If it is noisy there are quieter ones.

Verify insulation on bathroom ceiling and improve to reduce condensation.

 

[BathDIY]

Have just redone the insulation beefing it up to 27cm, this did help. Have also just sorted insulation under preexisting boards covering part of the loft in some places, there was no insulation at all. Here it's only 10cm as the joists are piddly and it's all I can put down without removing the boards altogether.