Extractor fan

[cegueira]

I have an extractor fan in a a shower room that is not clearing the condensation, the current extractor fan is too low down on the wall. I have set the overrun for as long as possible and cleaned out the fan. The shower room is on the first floor at the corner of the house with two exterior walls.

Untitled

• cegueira
• 21 Nov 2014
• 1

A builder has suggested fitting a fan with a humidistat higher up the wall and closer to the shower. However lots of people online seem to suggest just using a timer and setting it properly, is this recommended?

The room is ~9m3

 

[jeds]

However lots of people online seem to suggest just using a timer and setting it properly, is this recommended?

But you said you have already set the overrun for as long as possible??

 

[Taylortwocities]

The throughput of the fan may not be enough. Think about one with more grunt.
Also, don't forget that you have a 100mm dia hole through your wall.
You must let at least an equivalent amount of air into the room, or the fan will just be trying to make a vacuum.


PS You should tell the tiler that he needs to go to Specsavers.

 

[cegueira]

But you said you have already set the overrun for as long as possible??

Yes, but the fan is too low to get the humid air. The builder is thinking about putting a fan on the wall close to the ceiling and closer to the shower.

The throughput of the fan may not be enough. Think about one with more grunt.
Also, don't forget that you have a 100mm dia hole through your wall.
You must let at least an equivalent amount of air into the room, or the fan will just be trying to make a vacuum.

The shower room window on the other wall has been fully open and there is a 10mm gap under the shower room door.

PS You should tell the tiler that he needs to go to Specsavers.

The bodger who used to live here should have a lot worse done to him than just being forced to go get some new specs!

 

[EFLImpudence]

The shower room window on the other wall has been fully open and there is a 10mm gap under the shower room door.

Then you have a more fundamental problem.

A fan is not the solution.

 

[cegueira]

The shower room window on the other wall has been fully open and there is a 10mm gap under the shower room door.

Then you have a more fundamental problem.

A fan is not the solution.

What is the solution? I don't think the current fan is powerful enough and I also think it's incorrectly placed.

 

[EFLImpudence]

Well, I was assuming you have excessive condensation but I suppose it is relative.

Is that mold on the ceiling and the surface flaking?
If so then it is likely to be more than condensation from the shower.

There may be a leak leading to permanent moisture somewhere or the rest of the house is excessively humid leading to constant condensation in the cooler shower room.

 

[cegueira]

That is mould, it is just underneath that patch that the builder has suggested installing a new fan . There are no leaks what level of humidity is normal in the house?

 

[EFLImpudence]

That is mould, it is just underneath that patch that the builder has suggested installing a new fan .

Is the loft above?
If so, is it really cold along that side? Rain blowing in?

How long does the condensation take to clear after a shower?
Do you wipe up the condensation in the shower room and leave the sopping cloth there?

The other wall - by the warm light - looks better.

There are no leaks

Ok.

what level of humidity is normal in the house?

I don't know a specific level.
It depends how warm and ventilated you have the house.

Some people have lots of plants, dry their washing, fish tank bubbling away, lots of gas cooking, totally sealed by modern doors and windows which are never opened.

The humidity will naturally condense on the cool parts.

 

[ericmark]

Temperature of the room has as much to do with condensation as the amount of moisture in the air. My office where I am typing this is 22.5°C at 48% humidity outside 10°C at 95% humidity. So any surface in the office at 12°C or lower will get wet and any where outside a 8.9°C will get wet that is the dew point.

So there comes a point where simply pumping more air just makes the room cooler and gets the walls below the dew point.

Capturing some of the heat leaving and transferring it into the fresh air in the room will help keep the room warmer. Also ensuring the replacement air is as dry as it can be to start with.

If I take the humidity meter to my father-in-laws house he is more like 75% as he has well sealing doors and windows and cooks on gas.

When I lived in Hong Kong mould was a huge problem as outside was hotter than inside and moisture was only removed using an air conditioner.

So likely a heat recovery unit will work better than a simple fan as return air is from outside so likely a lower dew point than air taken from inside the house. As I say in my office the air has a dew point 3°C higher than the air outside so replacing bathroom air with air from my office would not be as good as replacing it with air from outside.

There are two basic types of heat recovery units. Those with twin fans very large box and those with a single fan and the heat exchanger is built into the pipe going outside. It will depend on build of your house but it may be better to try and get walls warmer rather than pumping out more air heated by your central heating.

 

[Steve]

If you want a more powerful fan, try a centrifugal fan. I have one, it is very powerful, but sits bigger on the wall than yours (but will cover the poor tiling). They are louder though, don't wire it in with the light or you'll be waking everyone up during the night.

However, unless you fit a couple of these:

At either end of the room, one sucking and one blowing, you'll always get a bit of condensation on tiled walls. The one regret I have about when I refurbed my bathroom was that I didn't insulate the walls. I even had all the plaster off the walls. Just boarded and tiled. This is the main thing you can do to reduce condensation.

I have a cupboard in the front bedroom above the stairs. The old boiler used to be in there - very warm. When the boiler was removed we found we were getting a lot of condensation, damp and spore growth due to the cold walls and still warm air. Last year I decided to do a bit of work to improve things. I framed out the walls, pushed in some polystyrene insulation boards (50mm) and covered it with a membrane and MDF (for cost purposes). No damp since. And its warm in there. The ideal is 100mm of insulation but I couldn't afford to loose this much space in the cupboard. It is now my computer den - just big enough for a chair (if I sit at an angle).

Oh, and insulate the ceiling thoroughly. 300mm if you can.

 

[cegueira]

When we first moved in I realised that there was a recessed incandescent (non IP) bulb directly above the shower and then a 3 spot incandescent in the centre of the ceiling, zone 2. After getting these replaced with properly IP rated units the condensation was then trapped in the shower room rather than being vented into the loft.

The ceiling is papered, so I'm wondering if a solution could be to get a more powerful extractor fan, and then plaster the ceiling and paint it with some mould resistant paint designed for kitchen or bathroom use.

Does the placement of the fan really affect it's ability to get rid of the humid air?

 

[ban-all-sheds]

After getting these replaced with properly IP rated units the condensation was then trapped in the shower room rather than being vented into the loft.

Just as well - it's a lot easier to deal with condensation and mould that it is rotten roof timbers

The ceiling is papered, so I'm wondering if a solution could be to get a more powerful extractor fan, and then plaster the ceiling and paint it with some mould resistant paint designed for kitchen or bathroom use.

If you want to try that surely you can just paint over the paper?

But that sort of paint "resists" mould, not "prevents" it. And "resists" can mean anything. Newspaper, for example, is water resistant. Just not very, and not for long.

At the end of the day it is simple physics, and no amount of fiddling with insulation, special paints etc will do anything about the fact that breathing, cooking, washing etc all put water vapour into the air. Unless you want to stop breathing, cooking, washing etc you have to take the moist air out of the house and replace it with dry air, or all that water vapour will make an appearance somewhere - it has to.

Does the placement of the fan really affect it's ability to get rid of the humid air?

I doubt it, as long as it's powerful enough. If you're worried that that might be a problem with yours, get some joss sticks and see if it drags smoke down from the ceiling.

 

[cegueira]

If you want to try that surely you can just paint over the paper?

Maybe I should try that first, although it's starting to bubble in areas. With the amount of other work we want to do around the house I wouldn't mind a temporary solution for the shower room.

So I will try the joss sticks to see if it can pull the smoke from the ceiling, but it looks like the thing to do is replace the extractor fan with a better one and paint the ceiling.

 

[ban-all-sheds]

What about extracting through the ceiling, with a fan in the loft?

Free of the constraints of an in-wall one you could put a large powerful one up there.