Replacing rockwool/fibreglass insulation with kingspan

[martcol]

Hi,

My attic is fully boarded - tongue and groove over 4x2 joists. The previous owner has laid 10" rockwool/fibreglass over the boards, making the roof space unuseable.

I thought to remove the fibreglass, replace with Kingspan or similar and board over the top, creating a useable space, but having equivalent insulation, for the EPC when I come to sell.

Does this seem sensible? If so, How do I know how thick the Kingspan sheets should be? Is (say) 50mm Kingspan, foil on both sides, equivalent to 10" rockwool? I can't seem to find the info anywhere?

Cheers.

 

[Cumbrianroofer30yrsexp]

I have "coolag" now known as celotex aka kingspan(i think ) in my loft 40 mm(its that size because it was free),between the joists and the spars,i dont even have any gaps for airflow but then again it was fitted back in the day Works good for me

 

[martcol]

I have "coolag" now known as celotex aka kingspan(i think ) in my loft 40 mm(its that size because it was free),between the joists and the spars,i dont even have any gaps for airflow but then again it was fitted back in the day Works good for me

Thanks. I was looking at 50mm sheets. It does seem quite difficult to find equivalent thicknesses, though.

 

[freddiemercurystwin]

More like 100+.

50mm is better than nothing but nowhere near equivelent to 10" Rockwool.

 

[mointainwalker]

100 mm of Rockwool has an R value of 2.5
100 mm of Kingspan has an R value of 4

so you would need 160 mm of KS to replace the Rockwool to achieve the same insulation value.

The foil is irrelevant.

I don't know if it makes any difference for the EPC. My experience is ( when renting my house and needing an EPC) that if they can't see it, they simply assume what was legal minimum when the house was built.

This is very much a box ticking exercise with no investigation.