Grade II listed? No problem
The Museum of Gloucester is a grade II listed building famous for its Romans kitchen playhouse and medieval street. Built in 1860 it was in need of a major refit, which included improving the energy efficiency of the boarded roof. Since raising the roof considerably was not considered an option, the chosen solution was to have a layer of TLX Gold 
used over the boarding, draped over counter battens with the tile battens going directly on top.
The problem: how to decide the best way to insulate a boarded roof given the financial and constructional constraints of the job.
The solution: TLX Gold can be used directly over the boarded roof, draped over 50mm counter battens, to leave an unventilated air gap between the low emissivity breathable under-surface and the boarding, giving a U value of 0.69 W/m2K. If it is possible to raise the roof then a continuous sheet of PIR between the two can reduce it much further âₓ to meet Building Regulations requirements of 0.18 W/m2K if 85mm PIR is used.
There is no condensation risk if a well-sealed ceiling is in place, and a risk analysis calculation can be carried out for other buildups, even including those which have additional insulation between the rafters such as might be necessary for new build designs.
