| 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. |
| thickness |  0.023 38mm batten |
0.021 No batten |
0.023 No batten |
| 40mm | 0.27 | 0.29 | 0.30 |
| 50mm | 0.24 | 0.25 | 0.27 |
| 60mm | 0.22 | 0.23 | 0.24 |
| 70mm | 0.20 | 0.20 | 0.22 |
