John White wrote:
klkbloke wrote:

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 ~£30 from Screwfix.

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.

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?

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

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.