Would a humidity sensor and fan be a good idea when putting a new bathroom in?

De-humidifiers are very expensive (the good ones) and you will have to wire the machine in safely, for obvious reasons. The most cost effective method, is an extracor fan, with a built-in timer. Ours switches off after 20 mins. I bought one of those Envirolight hygromers, new on ebay, which uses a AA battery

The most important consideration, if installing an extractor, is that you have an opening or vent, which allows a similar volume of air into the bathroom, to that which is being extracted out - otherwise the extractor is none too efficient.

Bertie

suppliers:-

I would suggest the humidistat controlled fans are much better than timed ones in this application. They only run when the humidity is above your pre-set level and not every time you turn the light on.

We did, and we're very pleased with it.

Quite so, though obviously it will have extracted some moisture while the shower was running.

I don't think so and then there's the bother of plumbing it in or emptying the collector. We have a heat-recovery fan that has an inlet and an outlet and warms the incoming air using the outgoing air. Whether that saves enough heat to be worth-while I couldn't say, but it certainly dehumidifies well, and I get the impression that it works better than a straight extractor when the door's closed, because it's not straining to suck air out of a sealed box.

On Fri, 25 Jan 2008 13:10:55 -0800 (PST) someone who may be 405 TD Estate wrote this:-

Possibly. There are a number of control strategies with two or three speed fans. For example the humidity sensor or a pull cord operating the fan at its highest speed. The fan manufacturers have a lot of information for people to peruse.

Another possibility is to fit a whole house heat recovery system.

There is much to be said for opening windows to let steam out.

Agh, thanks David, I didn't spot the window ref, in my earlier post. Ok, if an extractor is fitted, you won't necessarily need an inlet vent/duct - you could always open the window a crack, when the extractor is on. Obviously for greater efficiency, you would want to site the extractor, as far away from the window as possible.

Bertie

I fitted one with a built-in sensor and it is IMO the best way to ventilate a bathroom.

Colin Bignell

Is there any risk/tendency for them to cut in and out during the night?

We have an extractor fan in our en-suite which I deliberately wired up to a simpler on-off switch rather than a timer (which I'd have preferred), so that it wouldn't stay on during the night and keep SWMBO awake, but clearly it has limitations.

How appropriate would a humidistat be under these circumstances?

Thanks David

There does not seem to be... you may find you need to tweak the setting a little through the space of the year, but it is rare to find it working unexpectedly.

Should be fine. Having the RH control on them means you can always force the fan or on off if you want just by changing the target RH knob.

No risk of the fan coming on inadvertantly during the night, as you will adjust the pre-set level to come on when there is only steam in the bathroom. If you get the model (woth a pull cord) that robgraham mentions, you can over-ride the humidistat and operate the fan, as and when you need it. Pull cord - fan comes on. Pull cord again - fan goes off.

Bertie

The only conditions ours comes on is a steamy bathroom OR rain driving in through the grille and getting close to the sensor, OR when my *&^% wife has left the window open in a rainstorm.

In which case I want to be woken up.

Not true. You can get as much humidity from rain and standing water on the window cill.

If you get the model (woth a pull cord) that robgraham mentions,

A problem I have found with humidistat is that there is a big variation between summer and winter in the background indoor humidity.

This means if wrongly set up they can run and run in summer.

Ours is AFAIK not adjustable but has never come on or gone off unexpectedly. Don't ask me how, but it just works. The brand name is Eclipse.

On Sat, 26 Jan 2008 11:09:41 GMT someone who may be "Bertie Doe" wrote this:-

I don't think so. Far better to have an air inlet on the opposite side of the room.

Fan and window could well be side by side. The windows is going to be in an exterior wall and it is a good idea to vent the fan through the wall if possible. This means both are likely to end up on the same wall. Depending on circumstances one approach is to have the fan on while having a shower or bath and then turn it off and open the window.