I'm using 50mm Kingspan boards which although expensive are widely regarded as the best product for the job as they trap internal heat and reflect external heat during Summer....allegedly. The boards are very light and easy to cut but careful measuring is required to get a snug fit between both rafters and studwork.
Heres' a few pictures to show the work I have just started..... Talk amongst yourselves a little....This could take a while....
|The insulation boards going in under the eaves and the roof .|
|A 30mm gap is left between the tile laths and the Kingspan boards. This is to allow air to flow around the underside of the roof and prevent dry rot forming in the roof timbers.|