Condensation in loft above Bathroom.

[Staglemon]

I have read the sticky and tried using the extractor fan to help cure the condensation in the loft floor between the ceiling and the insulation but it isn't working.
I religiously open windows after using the bath or shower and so does my family. We also use the extractor but to no avail.

Could it be the insulation needs changing? If so just replace it with the same material (fibre glass wool) or change the insulation type?
I would rather not do the latter as I would probably need to then redo the whole loft and I think I would lose heat by changing the type.

 

[JohnD]

how long do you run the fan for? does it go straight through the wall or what? Opening windows will prevent the extractor creating suction so is not a good idea while the fan is running.

Are there any steam-vent holes in the bathroom ceiling to take the moisture through? these are usually made by people installing downlighters, sometimes they are around pipes that go through the ceiling.

how is the loft space ventilated?

 

[Staglemon]

On further investigation it seems its not just above the bathroom. I have a few boards that have compressed the insulation in places but it certainly doesnt cover the loft. Its mainly wet under the boards. I may have to attempt to raise the boards above the insulation somehow to solve that problem to stop the insulation 'sweating'.

My house is a newly built barn conversion and the builders have put down lights everywhere. in the bedrooms, bathroom, kitchen and lounge.

The loft is naturally vented via a kind of grill that runs around the whole of the loft edge.
An the fan only runs for about 5 minutes after the light is turned off and it discharges straight out the wall.

 

[JohnD]

I recommend you put hoods over the downlights. You can get fire-resistant smoke-hoods, which allow you to put insulation over the hoods as they create a space as well as preventing smoke or steam rising into the loft.

If you have more time than money, you could make box enclosures with plasterboard, which is also fire resistant and very easy to score and snap to shape and size.

You can enable airflow under the boarding by putting battens across the timbers.

You might be able to increase the overrun on the fan, depending on make or model. They will often adjust up to 20mins. But block the movement of warm moist air through the ceiling as your first move.

 

[Staglemon]

The insulation is actually higher than the horizontal timbers. Any ideas how I could get over that before laying battens?

I have more time than money so then plasterboard hoods sound like the way to for for that. Should I just seal them with a simple heat proof sealant or is there a special type?

Thanks so far.

 

[JohnD]

If it was me, I would nail the joints (might use wood battens inside) and seal any cracks or gaps with multifinish plaster (it does not need much in the way of strength)

For cross-battening my own loft, I used 70mmx35mm timbers, which also spreads the weight over several roof timbers and gives more rigidity when they are all screwed together, and prevents sags when I walk about up there. I also laid the second layer of insulation between the battens, at right-angles to the insulation between the loft timbers. This reduces risk of gaps or thin patches.

You could consider drilling 20mm ventilation holes in the flooring above any sources of warm moist air, but it will probably not be necessary.

 

[geraldthehamster]

I recommend you put hoods over the downlights. You can get fire-resistant smoke-hoods, which allow you to put insulation over the hoods as they create a space as well as preventing smoke or steam rising into the loft.

Also, is there a vapour barrier on the warm side of the insulation (e.g. a plastic sheet under it, on top of the ceiling)? If not, your warm moist air is rising through the ceiling and condensing in the insulation.

Cheers
Richard