Attic conversion refurbishment

D13exile

Hi

Just bought a house with an attic conversion which I think was done a long time ago judging by the decor. I had a structural engineer check it out to see if it was done properly and he confirmed it was with the correct steel joists etc. However while I was up there yesterday, it was stifling hot which leads me to think that there's poor insulation above the timber ceiling, i.e. just fibreglass that's probably compacted or nothing at all? The ceiling has wood cladding on it that I hate as it sucks the light out of the space. Finally there's two velux windows that may need replacing as the seals appear to be perished?

So my question is, what would it cost to take down the wooden ceiling, reinsulate with kingspan and then slab over? Attic room is 5.2m x 3.7m in area.

Looking at a few grand.

I think if the room is that hot, replacement with kingspan will have to be in the rafter and removal from the joists, so if it is only quilt it should be easy. I would also look at correct ventilation there if your looking at removal of the wood panels