From the picture you can see the insulated board behind the plasterboard. At the top of the plasterboard I was lowering the centre of the ceiling as the picture shows a piece of insulation in place as a guide. Now I am putting more plasterboard up to the level of the blue plasterboard to have the ceiling that bit higher. The reason to change the ceiling height is so I can install the lighting I want. By the time I am finished I will have all my lighting on LED lights but also being run from solar energy, but that's another story.