dreamroof is a sprayfoam product that will insulate your roof walls floors, its very good but if your spraying your loft and you just have the lime render type finish without any felt then the roof cannot breathe causing damp to rot the timbers, for more info on this product try www.expandingfoamkits.co.uk
Lime torching is not very common and was used to bind the underside of tiles to the battens and reduce wind driven water ingress and subsequently airflow.
However it is not the presence of lime that is the problem but the fact the airflow was subsequently limited. Good ventilation is vital to the health of the timbers in the roof so ventilation should be a consideration at all times.
By creating a warmer roof void condensation can be dramatically reduced especially id air flow is maintained.
Dreamroof guarantee their work for ten years and exercise care to ensure a roof remains well ventilated. The Sprayfoam is breathable too. As with any professional organisation it is still the quality and experience of the tradesman that counts!