The consultations set out clear worst case U-values which roofs on all new homes will need to meet.
These are 0.13 W/m2K in Wales and 0.16 W/m2K in England. It is highly recommended, however, that installers look to go above and beyond these minimum requirements. Roofs can act as a key source of heat loss on a property, and by insulating them correctly from the outset, it is possible to achieve significant energy and cost savings year-on-year. This is even more important with performance targets for existing homes also set to tighten over the coming years. By getting the envelope right from the start, you can allow customers to avoid costly insulation refurbishment work further down the line and ensure you are properly prepared for the future changes.
We would suggest adopting a U-value of 0.11 W/m2K which is the value proposed in the notional dwelling for both Welsh consultation options. By using Polyisocyanurate (PIR) insulation, which has a low thermal conductivity and is therefore a more effective insulant than hybrid alternatives which use materials such as mineral fibre, it is possible to keep the construction slim whilst hitting this target.
Building Innovation can work with you to develop a fully calculated tapered or flat roof scheme which meets both your requirements, and those of the Building Regulations/Standards.