Awkward extractor fan venting

[msmsm]

Hi,

I have an awkward extractor fan venting problem;I don't know the best way to get the ducting out the house.

The extractor fan is fitted in the bathroom loft space and uses flexible ducting to extract from the bathroom. This has all fitted and wired in professionally. However, the extraction point proved a problem and still does!

The house is an old Victorian house. The roof is slate but I cannot not see them from within the roof as rather than felt there are large boards to which the slates are nailed to. I don't see how I could drill through one of these without compromising its integrity so it rules out a tile vent.

There are no soffits. The rafters emerge through the wall and the ceiling basically intersects the roof.

There is a slight gap of a single brick between the roof and the ceiling; It is through a small gap in this that the fan currently vents but this has 2 problems:

1) It vents to the outside, but to an area that is enclosed by the fascia board and roof overhang (the bottom is open). Will this be a problem as my worry was the warm air would come out the extractor, fill up this area and then work its way back into the loft? Or will it cool enough quickly enough to not do this?

2) The hole it vents to is far too small and so the extractor fan is next to useless.

I have managed to make the hole a bit bigger (I removed the rest of the half brick that was there) so the hole is now approx 100mm x 60mm. This should be big enough to fit flexible ducting through. If I bring this ducting below the level of the fascia and vent downwards do you think that the steam will rise back into the fascia/roof gap or should I be OK?

I hope this explanation is good enough. I have attached a very elementary image. Any advise would be greatly appreciated!

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• msmsm
• 10 Apr 2013
• 1

Matt

 

[Charnwood]

What's the depth of the fascia, and would it be feasible to vent through it, attaching a louvre grill to it?

 

[stem]

That's one of the most common way of venting bathroom fans.

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• stem
• 22 Sep 2010
• 6

You need to make sure that the warm moist air is vented away from the building structure to avoid damp / damage to the structure, so the bottom (soffit) will need to be filled, you probably don't need to do the whole run to achieve this, just the area around the outlet where the moisture is emitted.

An alternative is to go through the slates, in can be done, but is probably best done professionally not DIY

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• stem
• 22 Sep 2010
• 4

Or how about using some plastic soil pipe and fittings so that the vent protrudes from below. If it's done neatly, I think it will look OK, no worse than the condensing boiler 'periscope flues' that are appearing everywhere. The drawing below shows the concept. You could extend the flexible duct further if you can't get the rigid duct through the small hole. The soil pipe is the correct diameter and you can seal the grill to the end with a 'no nails' type product.

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• stem
• 10 Apr 2013
• 1

 

[msmsm]

Thanks for the help.

If I could fit a vent in the fascia that was not obstructed by the guttering would this be OK or would I still need to fit a soffit?

Otherwise I guess the best DIY route is to attach a short run of soffit where the ducting comes out. This should not be too difficult as the end of the rafters are exposed so I guess I could screw the soffit directly into this - it is what the fascia boards are attached to so I guess that would be OK?

I considered going the vent tile route until I remembered my roof is boarded rather than felt so I am not sure about the feasibility of going through one of these boards with a 4in hole. I have a slipped slate so I will probably hold off doing anything until the roofer has come round to fit that and I can talk to him about whether the roof vent approach is possible.

EDIT:

I just saw your edit to the above post. This looks like a decent idea; so basically I am venting directly away from the house below the line of the soffit; I am guessing it is unlikely that any significant steam would blow back and up into the void?
Matt

 

[stem]

If I could fit a vent in the fascia that was not obstructed by the guttering would this be OK or would I still need to fit a soffit?

That would probably be OK, certainly much better than what you have now.

so basically I am venting directly away from the house below the line of the soffit; I am guessing it is unlikely that any significant steam would blow back and up into the void?

That's the idea