Kingspan or fiberglass for drywall/single brick

[andrewgray123]

Hi guys, I'm new here, I'm currently undertaking a shed conversion, into a dining room...
I've got a single skim wall shed, this has the dpc as expected at the bottom, I've visqueened the full shed, battoned it all out with 3x2 and plumbed/leveled my battons.
My next step would be... Install 75mm kingspan (3inch) then plasterboard (probably foil backed for an extra moisture barrier, meaning it's watertight, insulated, and ready for plaster However at £30 a sheet it's going to cost a fortune. I'll be looking at over £300 in kingspan or celotex.
I've got a load of fiberglass loft insulation at work which will cost nothing.
How well does fiberglass hold up against kingspan? And how would it work in a drywall situation? Obviously it's designed for a loft. But how does it work in walls? And what is its insulation value like in comparison to kingspan.
Any help would be greatly appreciated.
Kind regards
Andy

 

[noseall]

However at £30 a sheet it's going to cost a fortune. I'll be looking at over £300 in kingspan or celotex.

...and the bad news is 75mm will not be enough to satisfy b'regs/latest thermal standards.

 

[andrewgray123]

As this is an outhouse and an existing structure, it is a DIY project it will be done by myself and won't be going through b/regs... If I am doing it with the 75mm insulation. What difference would there be between kingspan and the fiberglass? Is it really worth the extra cash
Thanks

Ansy

 

[tomfe]

If you are converting an existing space into a heated habitable room you still need building regs regardless.
Fiber glass is about 1/2 as efficient as a ridard pu board but £300 is a lot of heating so maybe 4 years payback.

Maybe do it right the first time and then you know you it's all legit and when you sell it wont come back at you?

 

[flameport]

Obviously it's designed for a loft. But how does it work in walls?

Rather poorly, since it will tend to sag and end up in a heap at the bottom of the cavity.

I've visqueened the full shed, battoned it all out with 3x2 and plumbed/leveled my battons.

Vapour barrier goes on after the insulation, it's purpose is to prevent moisture entering the insulation and causing condensation on the cold side.
If you put in on the walls and then insulate, moisture will enter the insulation, condense when it reaches the cold vapour barrier and result in the insulation being a wet and mouldy mess after a few months.