Adding conservatory roof insulation using standard rockwall or fibreglass can cause more problems than it solves.
This technique includes screwing foil insulation to the underside of the roof then covering with plasterboard and decorated. It should be noted that this does tend to make the conservatory much more usable however there often problems.....
Leaking or condensation from the original roof can form on the underside of the roof, therefore, making the insulation damp. The worrying part is the first the home owner would realise there is a problem is when the water damages the plasterboard. They would then need to be replaced. This can be a messy job!!
Damage or movement to structure
One of the most significant problems with this method is the thermal expansion and contraction which will cause the conservatory frame to move. It should be recognised that this will only be a small amount, however enough to crack the plaster and require frequent repair and decoration.