Existing buildings
Approved Documents L1B & L2B
Because existing buildings account for a substantial proportion of carbon dioxide emissions the revisions to Part L have raised performance standards for building fabric and services for extensions, material alterations and changes of use – tables 08 and 09.
Table 08 Extensions & Renovations – U-values (W/m2K)
| Thermal element |
Newa |
Replacementb |
| Walls |
0.30 |
0.35 |
| Floors |
0.22 |
0.25 |
| Roofs |
|
|
| - Pitched |
|
|
| (rafters) |
0.20 |
0.20 |
| (joist) |
0.16 |
0.16 |
| - Flat |
0.20 |
0.25 |
| Windows |
1.8 |
2.0 |
| Doors |
3.0c/6.0d |
3.0c/6.0d |
aExtensions to non-dwellings which are greater than 100m2 in floor area and more than 25% of the floor area in the existing building come under ADL2A
bIf > 25% of surface area is to be renovated then whole element has to be upgraded to this level
cDwellings
dNon-dwellings
Table 09 Upgrade of retained thermal elements – U-values (W/m2K)
| Thermal element |
Threshold |
Improved |
| Cavity Wall |
0.70 |
0.55 |
| Other wall type |
0.70 |
0.35 |
| Floors |
0.70a/0.35b |
0.25 |
| Roofs |
|
|
| - Pitched |
|
|
| (rafters) |
0.35 |
0.20-0.25 |
| (joist) |
0.35a/0.16b |
0.16 |
| - Flat |
0.35 |
0.25 |
aDwellings
bNon - Dwellings
For buildings other than dwellings, work on extensions and initial fit out may require improvements to be made to existing services. Those ‘consequential improvements’ may cost as much as 10% of the proposed work. Increases in the capacity of heating or cooling plant will require consequential improvements to the thermal elements: there is no cost limit on such improvements, but they should have a payback period not exceeding 15 years.
