Bathroom extractor fan ineffective at clearing moisture

Cameron1983

Hi all

Just looking for some advice regarding my extractor fan. I have a 1st floor tenemant flat in glasgow, with a "closed" bathroom. I have had the extractor fan replaced twice now, but am still having problems with the amount of moisture which is now affecting the rest of the flat.

The fan is a standard extractor, mounted on a lowered ceiling. Im not sure how long the piping is to the exterior, but it is so ineffective that Im having to leave the bathroom door open. The fan is sited directly over the bath.

Would a continuous fan, centrifugal fan, extractor fan kit, or humidity sensor fan be best? Could the piping be blocked, as the amount of moisture seems really excessive (the fan does work, and Ive increased the timer setting)?

Thanks

keystone

Cameron1983 wrote: »

Im not sure how long the piping is to the exterior, but it is so ineffective that Im having to leave the bathroom door open.

Thats the crucial issue. You need to determine this in order to work out the fan requirement.

Cheers

moonrakerz

Most bathrooms are fitted with a 4" fan, which is just not big enough to properly vent even a smallish bathroom, especially as most people seem to set the timer on the fan to about 5 mins.
Equally important is to have a supply of air INTO the bathroom, either a wall grille or a gap under the door.

googler

We've got a 1st floor bathroom where the 4/5" fan vents via the attic space through the roof tiling; barely 1.5 metre pipe run, and we leave the fan on until we can visibly see the condensate has disappeared from the mirror. Also leave the window open and the door to allow dry air into the room from adjacent.

If your bathroom has a lower ceiling, is there any matching lowered ceiling in adjacent rooms, or box sections in the corner of rooms, that might lead the pipework to the outside? If you go outside your buildling and look at the windows of your flat, can you see an exit point for the fan duct?

This will help you determine the length of the pipework at least.

Solutions also include generating less condensate in the bathroom - take shorter showers; take colder showers. Depending on who else is in the flat, you could leave the door open whilst showering to allow the dry air in before condensates build up.

If you or anyone can reach the fan outlet where it exits the building, you could try tying a small piece of ribbon or similar onto it, and depending on how this moves when the fan is on, may tell you how much airflow is reaching the exit point.

Cameron1983

Thanks for those replies. The only room with a lowered ceiling is the bathroom, which is lowered to about 2/3 height. I'll try and find the exit for the extractor; problem with keeping the door open is that I think its caused some moisture and staining on the walls outside, and creating a slightly moist smell. Unfortunately the bathroom is small and completely enclosed, so no chance of fitting additional venting either.

googler

If there's no other access into the lower ceiling void space (between the lowered section and the original) then switch off the power, remove the fan unit from the ceiling, maybe detach it from the ducting, and shine a good strong torch or inspection light into the space to see where the ducting goes.

Hopefully you'll find it going somewhere, rather than merely venting into the void space itself......

iamcornholio

Cameron1983 wrote: »

...... but it is so ineffective that Im having to leave the bathroom door open.

That's a big no-no.

If you are having condensation issues in other pats of the flat, then the bathroom door needs to be kept closed at all times. And the fan should be put on a minimum 15 minute over-run.

Also, the bathroom door needs a 10mm gap at the bottom to allow air to be pulled into the bathroom by the fan.

You also need to have the window open when bathing and left slightly open at other times, along with any trickle vents

The fan is not a magical device which removes all moisture instantly, and you may need to understand this and do things differently ( in other parts of the property) to deal with condensation issues.

If the fan really is not effective, then you need to look at the length of any duct, bends or other choke points in the duct or outlet, and type of fan. A centrifugal fan will be more efficient with long duct lengths or multiple bends. A humidity sensor may help to bring the fan on at other times as necessary

However, a typical 100mm fan with a straight duct up to 2.5m, should be adequate for a domestic bathroom

googler

iamcornholio wrote: »

You also need to have the window open when bathing and left slightly open at other times, along with any trickle vents

No window - internal room.

dampdaveski

Cameron,
It sounds like you need an inline continous duty centrifugal fan such as the Nuaire Genie MX fan, if the inline fan is not what you need, then the standard 12 volt (as it's over the bath) Genie X fan wll help a lot more than the standard axial fan you have.
Centrifugal fans are more effective at overcoming resistance in long duct runs.
Just Google 'Genie X' and you'll find a raft of information and suppliers
Other centrifugal fans will probably be just as good, but I only have experience of the Nuaire products
hope this helps

Cameron1983

Thanks for the above. I looked inside the ceiling in the bathroom. The fan is connected to a rigid vertical plastic pipe, about 15cm in diameter going up through the ceiling. There are no vents to the front of the building, but to the rear there appear to be some small pipes with grills horizontally from the wall. I tried to attach a photo but not working. Anyway, a floor above and a room to the left of my flat there is a small grilled pipe coming out... I presume this is the exit, but would be several metres in length to my extractor - I wonder if this is why its so ineffective.

I phoned these folk up previously and was recommended: http://www.justfans.co.uk/extractor-fan-kits-c-85.html?osCsid=0970aba28219447f7f93b86ed2a8784f
these extractor fan kits - would you say a centrifugal one would be better for this length of piping?

NB. after reading a bit more about fans etc, it appears that better air entry into the bathroom may help - the door is a faily snug fit with no grills/windows etc in the room. Any ideas on how to improve air inflow? Wouldnt really be practical putting a grill through a wall, but maybe a thin one at the top or bottom of the door???

googler

The fact that the installers have fitted a rigid pipe would negate any theory about the extractor pipe being kinked, anyways.

I've seen gas installers use 'smoke matches' to test the efficiency of a chimney - I wonder if there's any mileage in starting your fan running, lighting a smoke match in the bathroom, and observing how much smoke reaches those external vents?

It seems they've led the extractor pipe out between your ceiling and the floorboards of the flat(s) above.......

Removing a section of the bathroom door, to install an air vent, or replacing the door with a part-louvred one may assist the air flow into the bathroom, as long as we can establish a good rate of flow out from the fan .....