The Department for Business Energy & Industrial Strategy has published a new guiden documement which seeks to provide best practice guidance for the installation of room in roof insulation.
The guidelines, which have been much requested, address the issues of how installations should be carried out in accordance to the PAS 2030 and PAS 2035 standards.
There are sections on ventilation, vapour permiable membranes, termal bridging, etc and much has been written specifically with the various roles of PAS 2035 in mind (retrofit assessor or surveyor, retrofit designer, or retrofit installer).
This is a must read document for anyone involved in Room-in-Roof Insulation, and can be downloaded from the government website https://www.gov.uk/government/publications/room-in-roof-insulation-riri-best-practice