Bathroom extractor fan controlled by humidistat?

[AmyByTheTrain]

In an effort to control our condensation and mould, we're finally thinking of getting an extractor fan in our bathroom. I'm wondering about the ones controlled by a humidistat. Does anyone have one, and if so, what do you think of it?

DH is convinced if we get one, it won't seal off well enough from the outside, and will just erroneously turn on every time it rains. I'm hoping they are a little bit better than that

if you have a space above the ceiling (or perhaps an airing cupboard) look at inline (ducted) extractor fans. They are larger and uglier, but typically three times as powerful and half as noisy.

There are some people who are reluctant to turn on fans. A modern extractor will run for between 50 and 120 hours on 14p worth of electricity. I would go for one that comes on with the light switch and runs on afterwards using its timer. It will keep the bathroom fresher than a humidstat

That's interesting about the ducted fans. We live in a typical 3-bedroom 30's house, so the bathroom is on the first floor, with two external walls, the loft above, and an airing cupboard. So, that's interesting to know about the ducted fans, because so far we were assuming we'd send it straight out the wall.

I'm wary of timer fans because I know I take showers that are too hot and too long . I'm worried that the fan will stop running before it's done the job. The one we had in a flat we rented a few years back, which was on a timer and connected to the light switch, didn't clear the air as much as we would have liked. I know it could have just been underpowered, but it was a fairly decent and modern flat, so I'm guessing it was reasonable.

DH doesn't want a fan that we have to switch off manually, because he worries we'll forget to switch it off. So, I was hoping a humidistat controller would be a good compromise.

I suppose having it on a timer and connected to the light is probably best, we just need to get one powerful enough to cope with lots of steam.

A timer fan (usually) is wired so it comes on when you turn on the light. It runs all the time the light is on, than adds on a preset time before it turns off.

Here and here are some examples (ignore the little budget ones). Read the reviews because one of the major brands gets much better customer comment than the other. Look at the air throughput, in cubic metres per hour (a typical cheap builders fan is rated at 80, but look for two or three times as much) and at the noise output in db. When a fan is outside the room, in the loft, preferably mounted on a padded board, you are additionally removed from the sound.

Yikes, thanks for pointing this out. Our DIY book has a guide to calculate how much throughput you need, which I lazily hadn't actually done, assuming a "normal" bathroom fan would do the trick.

Now that you prompted me to do the calculation, I see what you mean -- we should have 207-276 cubic meters per hour, which just like you say, is nowhere near what the fans I was looking at can do.

Well, that was an eye-opener. Thanks!

We bought a 'Silent' humidity fan as the shower room was very small, about twice the size of the shower enclosure, so an automatic humidity fan seemed a good idea. However with the room full of steam and condensation running down the walls and our humidity meter (separate unit bought to check the problem) reading 85% it does not come on with the setting at the lowest level or any other level. It is very easy for the manufacturer to say 'the customer does not understand how it works' but we do understand how it should work. Unfortunately we had it too long before installing it so could not return it. Also the feed wire buried in the wall was 2 core + earth, all that was needed for this fan, so we cannot easily change to a standard light operated fan which needs 3 core + earth. Our only solution seems to be to buy another brand. Take care.