What material?

[Jurek]

Bathroom has an air brick in the wall.
Externally, this has an iron grille.
Internally, it used to have a grille made from some sort of ceramic material.
When the bathroom was refurbished this was replaced with a stainless grille.
The problem with this is that the stainless doesn't provide much of a thermal break between to cold air outdoors and the warmer air indoors.
Condensation forms on the surface of the stainless. This then drips and runs down the mirrors, making them look skanky.
What material could I place between the two grilles that would act as a thermal break, without compromising the airflow?

[mrcharly-YHT]

I don't think you can.

Options to fix this properly; heat exchange extractor fan, standard extractor with a closing vent on the outside, erm that's about it.

You could replace the metal grill with a plastic one, but I still think you'll get condensation.

[Polar Bear]

I was thinking extractor fan too.  That bathroom must be brass monkeys in the winter.

[Jurek]

When it gets properly cold, the louvres get some closed-cell foam pushed into them.

[Canardly]

There used to be an air brick manufactured which contained chamfered rigid insulation in two halves with a slope between the two downwards towards the external face. The idea being that the dew point occured part way within the insulation and any resultant moisture would trickle to the outside. They must have also been vapour permeable. They were however also made from a plastic casing so an internal cover would still be required if they are indeed still available. Otherwise you could try making your own from a rigid board.

[Jurek]

I was wondering whether the condensation would be reduced if I filled the space between the two grilles with bath sponge.

[CarlF]

Some sort of heater to keep the inside grille warm (in the vein of a demister pad for the back of a mirror) ought to do it.

No idea if anyone sells such a thing, so it might require some inventive DIY.

How warm does the trace wire for stopping pipes and gutters from freezing get?

[Kim]

Why does the outside air always want to come *in* to the bathroom anyway?  It would be much more convenient (and smell better) if it went the other way.

[Peter]

Just worked out about the mirrors.....!

[rafletcher]

Plastic covers no good?

https://www.amazon.co.uk/Air-Vent-Covers-Walls/s?k=Air+Vent+Covers+for+Walls

[Jurek]

Just worked out about the mirrors.....!

It's the smallest bathroom the world.
It's my best attempt at getting it to look bigger than it is.

[Von Broad]

What's the history of that room?
Is it a basement room?
Has it always been a bathroom [I doubt it somehow].
But I see the window.....so in the summer, ventilation is not a problem [unless it's a security risk to have an opening window].
Not sure what the point of that vent is, it's not going to give you much airflow anyway.
Bit of a faff getting access to the wiring I guess, but an extractor fan is a must I'd say. Obviously, you'll be extracting warm air away from the room and drawing air from the house, but that's what all fans do!! And an external closing vent and closing flaps on the fan will resolve any cold air entering the room in winter too.

[robgul]

Extractor fan as suggested - with a "flap cover" on the outside ... BUT as you have a rectangular aperture there will be challenges in fitting as most are round, or square with a round fan . . . and you'd need to get electricity and switching to it.

What's above the bathroom? - if it's a loft can you fit an extractor in the ceiling with a vent hose to the outside through the roof's soffit? (that would also make power supply easier from a light)

[Jurek]

Above the bathroom is the bathroom of the flat upstairs.
This is the ground floor of a Victorian conversion.

[Jurek]

[snip]
Not sure what the point of that vent is, [/snip]

This.

[Mrs Pingu]

I guess it was there because there was no extractor. If you can get an extractor you don't need it.

If you don't want to cut a big hole in the wall for an extractor you can get one built into a double glazed unit like what we had at the previous Igloo.
2018-08-27_08-44-06 by The Pingus, on Flickr

[Von Broad]

Above the bathroom is the bathroom of the flat upstairs.
This is the ground floor of a Victorian conversion.

Right. So the iron grille would suggest a very old installation - possibly way before extractor fans were even around.

So any wiring that needs to be done has to be done from inside your bathroom - which is not necessarily as bad a job as it sounds, although the hassle factor of the job will depend primarily on which direction the ceiling joists are running.......if they're running parallel to the mirrors, you're laughing!!

[Feanor]

I'm no expert in these matters, but I'll just comment that none of the bathrooms in any house I've lived in had a howling arctic windpipe, nor an extractor.
They were just like any other room.

If there is steamy moisture in the room after a bath or shower, you  just crack the window open a bit as you leave, for an hour or so. Or leave the door open and allow it to disperse un-noticed into the rest of the house. The modest quantity of steam is not noticeable as it disperses. The water remains in the air, not condensing out onto every freezing surface, because the room and the surfaces within it are maintained at a comfortable temperature, not at arctic outside air temperatures.

Personally, I'd fill the fucker with expanding foam. Lots of it

[Von Broad]

Or leave the door open and allow it to disperse un-noticed into the rest of the house.

Fans are also useful for extracting 'smells' to the outside as well though

[Feanor]

Or leave the door open and allow it to disperse un-noticed into the rest of the house.

Fans are also useful for extracting 'smells' to the outside as well though

As is a window.

[Kim]

Or leave the door open and allow it to disperse un-noticed into the rest of the house.

Fans are also useful for extracting 'smells' to the outside as well though

As is a window.

Unless the tendency is for air to flow inwards, which is how it works in our bathroom, and it seems in Jurek's.


Expanding foam seems like a good idea to me.  Or perhaps something more squirrel-resistant.

[cygnet]

Or perhaps something more squirrel-resistant.

[Von Broad]

Or leave the door open and allow it to disperse un-noticed into the rest of the house.

Fans are also useful for extracting 'smells' to the outside as well though

As is a window.

Sure.
But, depending on how many people occupy the flat, during a cold spell it's probably less than ideal to rely solely on a window.
It's one of those jobs where it's matter of preference what you do really, and whether you can be bothered.
Personally I'd put a timer fan in and run a cable over to the door for an isolating switch too, then you've got a choice as to how you want to control the air flow, whether it be by the window or a fan.
I'd certainly get rid of that vent though.

[HTFB]

Unless the tendency is for air to flow inwards, which is how it works in our bathroom, and it seems in Jurek's.

Expanding foam seems like a good idea to me.  Or perhaps something more squirrel-resistant.

Air flows outwards while you are running hot water, as it heats up and expands. Once you've finished your shower the hot saturated air starts to cool and cold air is dragged in (alongside air coming in from the door: it won't be a through draught). The cold condenses the vapour out before it can vent.

Extractor fans, or a steady source of heat like a towel rail that can drive slower two-way convection through the vent in between showers, are the answer^*. I really wouldn't want to have a bathroom that vented only internally. I spend enough time bleaching mildew off things as it is.

^*Or an MVHR, of course. [spooky] Join me! [/spooky]

[Feanor]

I really wouldn't want to have a bathroom that vented only internally. I spend enough time bleaching mildew off things as it is.

Yes indeed.
But would not simply opening a window for half an hour after a Steamy Incident not satisfy that requirement?
It does here.

I have no mildew, no condensation, and a bathroom at a comfortable temperature with no arctic ventilation.