Condensation in loft, mould on silver backed plasterboard

[fluff29]

Hi guys

looking for some more specific advice than the sticky gave.

Just before xmas found condensation forming on the silver backed plasterboard which lines my loft. There was mould spores starting to form as well.

We have slightly combed ceiling (probably about 2 feet). Got hubby to remove the insulation which was gathered at the eaves and hoped that would help.

Checked loft yesterday, condensation not as bad, however the mould spores have multiplied onto most of the silver backing. Is this anything to worry about?

Bought the house this year and this is what changes we have made to the loft:-

- installed a layer of space blanket running in opposite direction from the original fibreglass insulation.
- Floored the loft all the way in the centre of the loft.
- skylight was leaking, so just roofer to tile over.

Is there anything that we are doing wrong before we go down the expensive route of installing vent tiles?

The upvc eaves has a vent running the full length and I can see daylight when in the loft.

We still live the exact same lifestyle as we did in the previous house but never had this problem.

What causes the condensation? is it a lack of air circulating and will tile vents definately solve this?

thanks for any thoughts

fluff

 

[Chukka63]

the vents deff need to be clear.you could add a few vent tiles to aid air circulation.without pics its harder to assess what the exact problems could be.

 

[fluff29]

hi chukka63

Have already cleared the vents, but there is still condensation. will try to get pics tomorrow.

was sealing around all the old pipes which feed into the loft - just incase moisture is getting up the holes.

thanks

fluff

 

[mointainwalker]

Before you laid the extra insulation, did you check and see if there was a vapour barrier present with the original insulation ?

 

[fluff29]

Hi guys

Forgot to get pics again when i was up loft.

Still have heavy snow on the roof. Not alot of condensation at the moment but still lots of hairy mould on foil plasterboard.

Have put draught proof tape around loft door, sealed all holes in cupboards, etc to loft.

Also, spoke to roofer today about obtaining prices for vents.

Just don't want to spend all the money on the vents and this doesn't fix it.

When I was up in the loft tonight, it was cold up there but I could not feel any draughts. Could this be an indicator of no good ventilation?

BTW there is a barrier paper on the old rockwool on the bottom layer of the insulation.

thanks

fluff

 

[fluff29]

how many roof vent tiles would be recommended to ventilate a standard 3 bed detached house?

the house across the road has 3 low vents and 2 vents higher up between offset between the lower 3. these were apparently fitted by the previous owner who was a joiner and didn't do a very good job of cutting the felt inside the loft, therefore not sure if he chose the correct amount of vent.

is this the standard configuation?

we have vents the complete length of the fascia boards so not sure if we need the lower vents or would they not do any harm?

thanks

fluff

 

[mointainwalker]

i'm not honestly certain how effective the kraft paper barrier is anyway, but I would bet 1,000 pnds that it has just been roughly torn/cut to fit in between the rafters which still allows some moist air to penetrate. I have only ever once seen it installed corectly i.e. cut very accurately leaving overlapping paper at the sides which is then stapled at very close intervals to the rafters.

I would say invest 5-6 pnds in a pack or two of thin poly sheet from BNQ, spread it under the insulation, tape it where it joins using wide tape (50 mm)

It would be best under the original insualtion but might be o.k. under the new layer that you have added.

How thick is each of these two layers ?