Attic insulation

herlihyd

Hi guys looking to put kingspan insulation in between the rafters of my attic conversion, I have alot of condensation on the felt, it is breathable felt, I've had roofers, insulation guys up all telling me different things, use spray foam, dont use spray foam, use rock roll, stay away from rock wool etc two thing in common is they all say theres plenty of air but not enough ventilation, I'm wondering did anyone in the cork city area employ anyone to fit the kingspan in their attics.kind regards

GreeBo

If its ventilation you need, why are you adding insulation?

yellow hen

We have fibre glass in between the rafters of our attic conversion and it's gappy and extremely cold. Plus it's a bit messy in the space where we now have to put our regular boxes etc for attic storage. We were wondering if we should consider foam insulation. Is there any particular reason not to get foam insulation (other than cost)?

MicktheMan

herlihyd wrote: »

Hi guys looking to put kingspan insulation in between the rafters of my attic conversion, I have alot of condensation on the felt, it is breathable felt, I've had roofers, insulation guys up all telling me different things, use spray foam, dont use spray foam, use rock roll, stay away from rock wool etc two thing in common is they all say theres plenty of air but not enough ventilation, I'm wondering did anyone in the cork city area employ anyone to fit the kingspan in their attics.kind regards

What are you doing for air tightness?

MicktheMan

yellow hen wrote: »

We have fibre glass in between the rafters of our attic conversion and it's gappy and extremely cold. Plus it's a bit messy in the space where we now have to put our regular boxes etc for attic storage. We were wondering if we should consider foam insulation. Is there any particular reason not to get foam insulation (other than cost)?

If your attic conversion is not airtight, adding or changing your insulation will do nothing to reduce heat loss.

listermint

What I would do is make sure the existing roofing felt is in good nick. Then I would pack the rafter voids with Steico flex. It's a breathable insulation which allows moisture to escape. Then I would cover the rafters in a vapour barrier. You need ventilation for the space also so can do that via traditional wall vent or some mhrv or other.

Steico is super easy to work with environmental friendly.

There are Irish suppliers too , look them up I probably can't link with forum rules. But I've purchased this stuff and I find it excellent.

BryanF

Op what is causing the condensation? A lack of continuous vapour barrier on the warm side of the insulation.

Why is the condensation on the felt not dissipating? A lack of ventilation in the gap between the insulation and felt or above the breathable felt (is the roof double battened?)