Loft Condensation

[robj20]

Last year I replaced all the standard loft insulation with PIR boards and boarded the central section.
Today I've just been in the loft and there is a lot of condensation both on the underside of the roof membrane and on the underside of the PIR board that touches the plasterboard.

I'm not sure what to do any pointers?

Wonder if something like this would do the job

https://amzn.eu/d/8i8hGCo

 

[Reuben klang]

Last year I replaced all the standard loft insulation with PIR boards and boarded the central section.
Today I've just been in the loft and there is a lot of condensation both on the underside of the roof membrane and on the underside of the PIR board that touches the plasterboard.

I'm not sure what to do any pointers?

Wonder if something like this would do the job

https://amzn.eu/d/8i8hGCo

You haven’t blocked off any vents have you?

 

[Destination]

Did you board right to the eves or leave an airgap?

 

[Relentless81]

Make sure sure there is an air gap around the eaves
Make sure the hatch is properly sealed when closed
Make sure any current air bricks etc aren't blocked

If none of the above, look at lap vents for a quick easy DIY job but that won't solve how the moisture is getting there in the first place

 

[robj20]

You haven’t blocked off any vents have you?

There are no vents it's a 3 year old roof so breathable membrane. Though it has me wondering now as only the front side of the roof shows condensation and that has a different membrane than the back side.

Did you board right to the eves or leave an airgap?

No though I did put insulation fairly close to the edges, I have been up and chopped a few back to a larger gap.

I could look at sealing the loft hatch up better.

I have done some makeshift vents as well pushed some bits of down insulation between to open the membrane up to give better ventilation.

 

[BUDFORCE]

I had to replace my shower extractor van which is in the loft and foolishly just left the vent open, I thought it wouldn't do toouch harm.

Then it got really cold last week. Went into my loft, literally raining inside.

I've had to stick a dehumidifier up there, but to be fair that aside I don't think it's completely unusual for a lift to get a bit damp particularly when it gets cold.

 

[Mercenary Keyboard Warrior]

Pretty sure I posted about this being a risk in the other thread about energy costs
Moisture will work its way through the plasterboard, PIR will block the airflow unless you have a vent gap

Normal fibreglass insulation and chipboard etc will allow a little moisture to pass through

 

[koolpc]

Ventilation. Plenty of it needed in the loft. Plus, stop warm air getting in there too.

 

[BUDFORCE]

Ventilation. Plenty of it needed in the loft. Plus, stop warm air getting in there too.

Yea very true, we go up there quite a bit as I put in a proper telescopic folding loft ladder, use it for storage and I keep my guns up there, but yes every time I open up the hatch I can't help but think a load of warm moist air is getting up there to condense and cause damp

 

[happy_2008]

Last year I replaced all the standard loft insulation with PIR boards and boarded the central section.
Today I've just been in the loft and there is a lot of condensation both on the underside of the roof membrane and on the underside of the PIR board that touches the plasterboard.

I'm not sure what to do any pointers?

Wonder if something like this would do the job

https://amzn.eu/d/8i8hGCo

i bought 28 of these and they helped to get rid of the condensation.

 

[Slam62]

We had this and paid a roofer to put 6 proper vents in.

 

[koolpc]

We had this and paid a roofer to put 6 proper vents in.

This...100%

 

[ANDARIAL]

Though it has me wondering now as only the front side of the roof shows condensation and that has a different membrane than the back side.

could be,maybe one side is non breathable.We had this a few years back supplier sent half of one type and half of another make.Was like a river up there at times

 

[robj20]

could be,maybe one side is non breathable.We had this a few years back supplier sent half of one type and half of another make.Was like a river up there at times

This is what I'm thinking seeing as only one side has the issue.

Though more ventilation anyway is a good thing.

 

[Derek W]

Last year I replaced all the standard loft insulation with PIR boards and boarded the central section.
Today I've just been in the loft and there is a lot of condensation both on the underside of the roof membrane and on the underside of the PIR board that touches the plasterboard.

I'm not sure what to do any pointers?

Wonder if something like this would do the job

https://amzn.eu/d/8i8hGCo

Rip out what you've done and replace it with the fibre insulation. Although folk are mentioning get better ventilation in the attic space it doesn't deal with the issue of the warm air from the house rising through the ceiling and hitting the cold foil of the insulation. Once it reaches its dew point it'll condensate and eventually it'll knacker your plasterboard. The mineral wool insulation allows free movement of air and whatever heat that comes up through the roof so doesn't get a chance to condensate.

 

[DXP55]

A few years ago I replaced my loft hatch door with a made to measure steel one - It came insulated with the itchy stuff and me being a cleaver clogs put a sheet of that bubble foil stuff on top as I had it spare -Next time I opened loft hatch I got soaked as the foil created loads of condensation which half filled the loft door. so off it came.
I have also put double air brick in both front and back gables as well as a few of those polystyrene wedges in roof felt -Glad to say it's dry as anything.