Loft condensation above the bathroom

[sad2k]

Hi,
I guess a relatively typical issue -
I was installing the glass wool insulation in the loft and after having done the 1st layer (between the joists) there's now a lot of condensation on the roof roughly above the bathroom (I don't think I've seen that much before - see picture).
What's my best strategy for resolving this -
1) Bathroom has an ancient extractor fan - I'm not sure which type it is - axial? (see picture) Air goes through a ~3m run to the external wall. There's no duct inside that run - it's basically just a rectangular path. Should I replace this with a centrifugal fan first to deal with the humidity source?
2) ... Or should I deal with ventilation in the loft first by installing some vent tiles?
Any thoughts?

 

[JohnD]

I don't understand what you mean about the duct.

Does the fan vent into the loft?

 

[sad2k]

No, there's just a boxed part of the bedroom wall that goes toward the external wall, there's no kind of duct inside

 

[freddiemercurystwin]

Still unclear, is there a duct from the top of the extractor fan in the loft that leads to an outside wall or through the eaves?

 

[sad2k]

The extractor fan is not in the loft, it's in the bathroom - or rather at the bathroom end of this path between the external wall and the bathroom.
Loft is above it all.

 

[sad2k]

It's something like the attached picture

 

[JohnD]

If you mean there is no airtight duct, you must fit one

100mm flexible plastic is common, though rigid pipe is better as it does not trap dust, fluff and condensation, and you can tilt it slightly so any water runs outside

I can recommend a better fan but i find your photos and descriptions unclear.

 

[JohnD]

Are there holes in the ceiling, for example for downlighters or pipes?

 

[sad2k]

Ok that's what I thought. In terms of the fan, as I understand I need a centrifugal one for the long duct?

 

[sad2k]

Are there holes in the ceiling, for example for downlighters or pipes?

If you mean in the bathroom there's just a light

 

[JohnD]

You must close them. Steam will rise into the loft

(So will smoke and flame in the event of a fire)

 

[JohnD]

Ok that's what I thought. In terms of the fan, as I understand I need a centrifugal one for the long duct?

No

Do you have steamy showers?

Do you need a cheap one or a good one?

Could you fit a 150mm duct or must it be 100mm dia?

 

[sad2k]

No

Do you have steamy showers?

Do you need a cheap one or a good one?

A good one I think
We do use a bath quite a bit so I imagine some steam

 

[sad2k]

You must close them. Steam will rise into the loft

(So will smoke and flame in the event of a fire)

How do I 'close' the light? Put a cover on the loft side?

 

[sad2k]

Can be 150mm I checked