| Optimising internal living space |
| L1B states that: “Practical considerations with respect to an increase in structural thickness (particularly in terraced dwellings) may necessitate a lower performance target.” |
| The table below sets out U-values that can be achieved using RafterFit with different thicknesses of rigid board beneath rafters. |
| RafterFit with PIR | RafterFit with Phenolic Foam | |||
| U-value | breather membrane | 1F felt | breather membrane | 1F felt |
| 0.20 | 50mm | 60mm | 60mm | 70mm |
| 0.25 | 40mm | 40mm | 40mm | 50mm |
