Advice, please, on fitting a bathroom extractor fan.

[Nick Odell]

The scenario: a 1960s apartment with a windowless bathroom which looks a bit like this

Not shown on this stock plan is a hollow column which is on the wall behind the door hinge and goes from floor to ceiling and continues up and down from basement to roof carrying services between the floors. There is a ventilation grille in this column on the side which faces away from the bath and the opening door. There has never been an extractor fan in this bathroom and frankly the vent is insufficient and doesn't do very much to clear steam or prevent condensation.

My intention is to fit an extractor fan into the column in place of the vent and to insert a ventilation panel into the door to allow air to be sucked into the bathroom from elsewhere in the apartment when the extractor fan is working.

Any obvious pitfalls?

It's been suggested that installing the fan on the side of the column facing away from the bath would be less efficient than installing it on the side facing the bath. I'm not convinced it would make any difference when the bathroom door is closed but putting the fan in the new position would obstruct it when the door is open. If it were better for the fan to face the bath I could easily fit a blanking panel over the vent and cut a new hole for the extractor on the opposite side.

Clearly the column is intended to ventilate this and everybody else's bathrooms but are there likely to be any problems resulting from forcing damp air out in this way?

For the avoidance of doubt no building regulations apply since this is all taking place in a country which has never heard of the things but I want to do a good, safe and efficient installation in any case.

Any thoughts?

Thanks,

Nick

[newshound]

Not really enough information. When you say an apartment, do you mean what we (this being a UK group) would call a flat? Does this same column go through the flats above and below you? Pressurising it by adding your own fan will just force your damp air out into other flats. You say it goes up to the roof, but does it go out through the roof to a proper vent with a cowl, or is it actually just a services duct?

If it does have a proper cowl in the roof, then the right solution might be to fit a fan just below it, so that everyone's bathroom is ventilated. Ideally fitted by someone who knows what they are doing.

[tabbypurr]

A dehumidifer would avoid such complications

NT

[Mike Clarke]

My first thought is that I hope a fire never breaks out anywhere in that apartment block.

The duct running from basement to roof with a grill into every bathroom would act as a very effective chimney to spread flames and smoke through the whole building.

[Nick Odell]

Apologies for EstateAgentSpeak: yes, I mean a flat. The flat below has the same layout and a vent in the same duct; the flat above is modeled differently and the duct passes through the living room without any opening but I couldn't say what happens in the top floor nor see the end of the vent on the roof because of the physical layout and access/lack of access up there.

After what you said about pressurising, it's crossed my mind that the reason this has become more of a problem more recently might be because someone else has already installed a fan somewhere else. In which case I suppose we might be in a nuclear arms race to see which apartment - sorry, flat - has the biggest, suckiest extractor.

Nick

[Nick Odell]

That's something I hadn't thought of and is worth looking into. Thanks.

Nick

[Nick Odell]

Well, I did say that building regulations, as we know them, are non-existent. I know an "architect"[1] over there so I'll ask them.

Nick [1]In inverted commas because "architect" doesn't mean quite the same over there as it does over here.

[spuorgelgoog]

Simple enough to have a fire valve in the wall duct to each fan.

Owain

[GB]

Do you really need the ventilation panel in the door?

[newshound]

Yes, quite possibly.

Without knowing more about the scale or ownership details it is difficult to advise further. If there is just one occupier above and one below, you might be able to talk to them, but not if it is Grenfell scale. Is there a building owner? Maybe they could be persuaded with money to fit a fan at roof level. Talking to an architect is a good idea.

[newshound]

It is good practice to know where the replacement air is coming from.

[GB]

Round the edge of the door? Underneath? Most bathroom doors are not airtight in the first place.

[Mike Clarke]

Assuming the walls of the duct are sufficiently fire resistant.

[Andrew Gabriel]

These ducts through apartments usually have a variable speed fan at the top to maintain negative pressure in the duct (or sometimes a bank with several fans which get progressively switched in as necessary to maintain negative pressure). Thus they automatically adjust to the amount of air entering the duct, and this ensures exhaust air from one apartment is not entering another apartment.

My first thought would be that the roof fan has failed and needs maintenance.