What U Value does 150mm IKO enertherm ALU PIR board achieve for warm roof insulation between rafters? Having 150mm in between rafters achieves approximately 0.24w/m2K. Please see BBA for further guidance here. What is the laid weight of IKO slates? Does IKO Easyseal (2 layer system) have to be laid in 1 go or can I leave a day in between layers?