Extractor fan in bathroom.

[klkbloke]

Hi All, I've just moved to a house with a downstairs bathroom hence leaving a window open after a shower is no longer an option. I thought the best option would be to install an extractor fan while I'm putting in the new bathroom suite. However I have two questions...

1) I've seen a fan which operates on a humidistat, not connected to the light switch in anyway. Has anyone had experience of these? Are they any good. I'm looking at one for ~=A330 from Screwfix.

2) I have an airbrick - well it's actually cast iron. I was planning to knock that through and use that to install the fan. The question is, do I need to install a duct through the wall and a vent on the exterior wall? Or can I just install the fan on the interior wall only? I would prefer not to touch the outside of the house as the cast iron "brick" is quite ornate (and 80+ years old) and fits in with the rest of the house. Would I risk damp getting into the cavity? I'd assume I would be no better or worse than the current arrangement?

Cheers.

[Mary Fisher]

1) I've seen a fan which operates on a humidistat, not connected to the light switch in anyway. Has anyone had experience of these? Are they any good. I'm looking at one for ~£30 from Screwfix.

Ours is excellent, I can't recommend them highly enough. It's magic when you hear the (very low) noise come on when you're in the bath. Under the shower I never hear it at all.

Mary

[john2]

g at one for ~£30 from Screwfix.

There should be a air-pressure operated flap installed on the outside to prevent wind blowing in when the fan is off, otherwise the bathroom will be permanently cold. Doesn't the air brick vent the void between the floors.

john2

[Huge]

IME these are completely useless, and on windy days a freezing draught will howl through the fan. Get one with positive operation on the shutters.

[John White]

I've put in a few of these recently and would strongly recommend them. They have the great advantage of only switching on when they are needed.

Use can a double pole switch as an isolator, and wire it straight into the lighting circuit.

I would put a new flue through the wall away from the cast iron grill, and then leave the grill to ventilate the cavity.

John

[John White]

That's my experience as well. They also make a terrible racket on windy days.

Much better to get a fan with integral shutters and have a plain vent on the outside.

John

[Weatherlawyer]

I doubt he has a cavity. Old housing had little plumbing, lots of chimneys and few security worries, so they could rely on natural ventilation to air them. The vent in a must have for old property.

I'd hire a core drill and bore a new hole for the fan somewhere where the new feature would be hidden outside, if that was possible.

[John Rumm]

Yup, I have fitted a couple of the 4" ones. They seem to do what it says on the tin. You get in the shower - after a few mins the fan kicks in. It then runs for 30mins to an hour after until the room is dry again. You can tweek the sensitivity with a knob on the underside (you may need to do this from time to time if the weather changes dramatically)

As you suggest, if you don't line it then you will fill the cavity with water. You can get rectangular ducting (TLC stock it), and a short length ought to do it if you make sure it is sealed to the wall on the inside and goes through as far as the cast iron on the far side.

[John Rumm]

IIRC, the ones I fitted required fusing at 3A which meant I needed a FCU as well...

This air brick sounds more like the type that we have in our bathroom - it is simply connected through the wall to a louvered vent on the inside and serves as permenent room ventilation.

[John White]

Quite right. I meant to say "Use a double pole, switched FCU as an isolator, and ...".

I really should read what I write before I post it. :-(

Fair enough. I was going by the OP's reference to a cavity.

John

[klkbloke]

Hi All,

Thanks for the many responses. I'll try and answer the various points raised.

- it is a cavity wall (I checked before I bought the house).

- the fan is rated at 15w so connecting it to the lighting circuit (using a dp switch) is ok (AFAIK).

Basically there is a cast iron grill on the inside wall and one on the outside wall. My plan as it stands (unless someone persuades me any differently) is to install the fan on the inside and duct it to the outside grill so as not to encourage the damp into the cavity.

This would still leave a 3" X 5" area of the grill unobstructed by the fan.

I'm reluctant to put another whole through the wall as it feels a little ott. At present most of the ventilation to the bathroom is via this grill which is currently open to the cavity.

What do you think?

[Mary Fisher]

Spouse made a wooden panel on which to mount the fan which would close off the exposed grill and painted it to match the wall. There is ducting through the cavity of course.

Mary

[meow2222]

Partially blocking these vents is not a good idea.

small bathroom fans are really hopeless anyway, and not even worth switching on at bathtime.

Th real solution is to add a lock to the window that enables it to be locked quarter to half an inch ajar, so no-one can see in but some ventilation occurs.

Compared to a fan: cheaper to buy cheaper to install no run cost silent much longer lived and more reliable more pleasant in use.

NT

[chris French]

We had a similar arrangement in our old house, the internal airbrick was covered over in the renovations, never caused a problem.

not my experience at all. Had a 100mm inline van in the loft, venting the bathroom through the roof. operated by a humidistat. It worked very well, much better than the previous arrangement - a window. Never any problems with damp, mould etc.

[nafuk]

[meow2222]

sometimes it does, sometimes it doesnt, doesnt make it a good idea.

I wonder why. My 6 inch one was useless.

NT

[Huge]

don't top post!)

[Guy King]

The message from chris French contains these words:

These new tiny Transits are quite versatile, aren't they?

[Mary Fisher]

I saw a couple last weekend but our loft hatch wouldn't take one.

Mary

[Alan Holmes]

Join the club, hands up anyone who has read anything before they have pressed the 'send' button!

Alan