Evening gents, now that winters is soon upon us the thoughts have gotten round to trying to make an old (1920) stone converted house habitable… Like so many in Aberdeen when this house was converted little thought was given to insulation. Essentially what was the loft has been converted into rooms. So my daughters bedroom is a ‘box’ in the converted loft with eaves either side. The box walls have been insulated with mineral wool suspended and fixed between the room wall studs. As I’ve been flooring the eaves I’ve added more mineral wool between the floor joists and added flooring then added more mineral wool between the wall studs and covered with plasterboard. While I am in the eaves I have ‘easy’ access to the roof rafters so I am thinking of fitting some kingspan between these then covering with plasterboard. I’m trying to work out whether there is any point in fitting the kingspan or not or perhaps remove all the mineral wool behind the plasterboard and replace with kingspan. Has anyone done anything similar?? Suggestions, abuse welcome as always.

Don’t go mad or it’ll be wet through inside of six months. Houses of that vintage were designed to “breathe”.

Keep in mind that as you’re adding all this insulation and flooring you’re stunting air movement and ventilation and trapping damp and with it potential for rot

Cheers. It is a cold roof design with plenty of air circulating via the soffits and thought if I were to add kingspan between the rafters I would also leave the 50mm air gap which would be refreshed via the soffits. Suppose I’m trying to understand if its worth adding the additional kingspan between the rafters.

Yes cutting and placing Kingspan between rafters is a good idea- having a much higher level of insulation than the mineral wool. Maintain the 50mm gap between insulation and sarking and make sure there is adequate soffit ventilation

I have done it – it does help and have had no condensation issues despite not using a vapour barrier.

There is plenty of air circulation tho as the council insisted when I expanded the rooms out into the eaves that I put in loads of roof ventilators whch destroyed the air tightness of the roof – which reminds me – I must block some of them up to stop the drafts