Mold patches on bathroom ceiling in spite of working new extractor fan

11fernsroad

We recently chanaged extractor fan in our bathroom about 4 months ago.It is xpelair simply silent and works for 7 mins after switching off.Sparky said previous extractor fan was left open onto loft area and on his recommendation we paid to install venting duct to soffit as well.But over last two weeks we are having mold patches over the ceiling around extractor area.

What could be the reason?

tacpot12

7 minutes is not usually long enough to reduce the humidity. Increasing the timer will just waste energy most of the time, and still not clear the humidity when it is at its worst. You need a fan that is controlled by a humidistat, ideally the humidistat should be located where the mould is forming so that the fan runs until that area is dry enough that mould cannot grow. Your fan may also be in the wrong position to draw air though the area where the mould is forming, 

It's not clear from your post whether you paid to have ducting installed to vent via the soffit. It must be ducted, you will cause problems in your loft if it is not.

daivid

Whether you go for humidistat or not I recommend having the fan on a separate switch to the light. I went for an inline fan with a good flow rate on a separate switch to the light (and not on a timer), this seems to do the job, obviously it relies on remembering to switch the fan on and off manually but means you don't have to have the fan on when brushing teeth, or have the light on when showering in summer.

grumbler

11fernsroad said:

We recently chanaged extractor fan in our bathroom about 4 months ago.It is xpelair simply silent and works for 7 mins after switching off.Sparky said previous extractor fan was left open onto loft area and on his recommendation we paid to install venting duct to soffit as well.But over last two weeks we are having mold patches over the ceiling around extractor area.

What could be the reason?

Cold weather and poor loft insulation in this area.

greyteam1959

7 minute's overrun should be more like 15 minutes.

ComicGeek

Compared with the previous extract that had no ducting connected, the new extract fan is likely to be moving much less air out of the bathroom. Therefore needs to be running much longer rid of the same amount of moisture. Normal extract fans are rubbish in terms of air flow rate. 

It's good that it's not just being dumped into the loft any more, but you need to be running fan much longer, or have one with a humidistat. It will also be an issue if the bathroom is too cold, as the surfaces are colder and there's a high risk of surface condensation forming, particularly on the ceiling if the loft isn't well insulated.

neilmcl

Even with the best extractor fan you can still get condensation, and ultimately mould growth in a bathroom during the colder months. I always crack the window open, even in the middle of winter until the room fully clears. Also you could also try repainting the ceiling with an anti-mould paint.

Gunner276

I recently purchased a Ventaxia "Silent" fan. Turns out it has 2 settings, silent which moves hardly any air, and high power which is fairly quiet but moves a lot more air. Have a look and see if your fan has similar. 

Also I doubt 7 minutes is enough, especially on the silent setting!