Hi, I have a flat roof structure attached to my house which was a small Police station office many years ago. The structure joins to my neighbour who has an identical layout. The police station was split in half when the houses were sold. It is currently my home office. It is a brick cavity wall with a concrete (I assume block and beam) roof and wet plastered ceiling. There is no insulation at all and is very cold and chills the whole side of the house. I was wondering if anyone has any ideas for insulating this room. I have considered: 1. A cold roof with kingspan but worried about interstitial condensation complications with ventilation, vapour barrier. 2. Hot roof not really sure how to do this, just dot and dab the insulation on the existing ceiling? 3. Inverted roof. Insulation looks expensive but very easy. Will need to get neighbour involved. Any pointers would be greatly appreciated as the doesn't seem much info on a concrete flat roof. Thanks in advance.