Guide to the New Part L Building Regulations
After a long period of consultation within the building industry, the final version of the Part L (Conservation of Fuel and Power) document (2005) was released on 16th March 2006 as the instrument for improving the energy performance in all new buildings from 6th April 2006. Headlining these changes has been the aim to improve the energy performance of all new buildings, and alterations or extensions to existing buildings.
The new document has been revised into the following four sections:
- Part L1A work in new dwellings
- Part L1B work in existing dwellings
- Part L2A work in new buildings other than dwellings
- Part L2B work in existing buildings other than dwellings.
The focus of the new regulations for walls has moved away from prescribed 'U' values for each element of the building fabric and now requires a carbon emissions evaluation for the building as a whole. This will involve a substantial improvement in the required 'U' values for each building element, which is likely to move within an acceptable range dependent on the type of building and other related energy use solutions.
Here we concentrate on the new Part L1B regulations as they apply to alterations or extensions to existing dwellings for outer wall construction. Information on Part L1A for work in new dwellings and Part L1B for the renovation of existing dwellings will be published at a later date.
Why Changes in Part L Building Regulations?
This is the Government’s response to Global Warming. The new measures will save One Million tonnes of carbon per year 2010 equivalent to emissions from more than One Million semi-detached homes.
New regulations represent an average of 20% increased energy standards for new buildings. The new regulations taken together with changes to strengthen Building Regulations in 2002 will improve standards by 40%, cutting fuel bills by up to 40% for new homes built from 2006.
If you obtained planning permission before 1st April 2006, you have one year in which to commence your project. If you did not obtain planning permission before 1st April 2006, you will need to comply with the new regulations.
In order to help you comply with these regulations we, at Elliotts typically stock a range of
Celcon &
Thermalite light weight blocks,
Knauf, Rockwool &
Ecotherm insulation and
British Gypsum &
Lafarge plaster and plasterboards. For more information please contact our Insulation & Drylining Depot on 023 8062 3960.
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Partial Filled Cavity
- Brick outer leaf
- 50mm clear cavity
- 85mm Crown Dritherm cavity slab or
40mm Xtratherm Thin R XT/cw
- 100mm Celcon Plus standard block
- 12.5mm Plasterboard on dabs
- 0.29 W/mk
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Wall Construction using Celcon Solutions
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Fully Filled Cavity
- Brick outer leaf
- 50mm clear cavity
- 100mm Rocksilk Dritherm cavity slab or
100mm Crown Dritherm cavity slab
- 100mm Celcon Plus standard block
- 12.5mm Plasterboard on dabs with lightweight plaster
- 0.30 W/mk
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Partial Filled Cavity
- Brick outer leaf
- 50mm clear cavity
- 85mm Crown Dritherm cavity slab or
40mm Xtratherm Thin R XT/cw
- 100mm Thermalite Shield block
- 12.5mm Plasterboard on dabs
- 0.29 W/mk
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Wall Construction using Thermalite Solutions
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Fully Filled Cavity
- Brick outer leaf
- 50mm clear cavity
- 100mm Rocksilk Dritherm cavity slab or
100mm Crown Dritherm cavity slab
- 100mm Thermalite Shield block
- 12.5mm Plasterboard on dabs with lightweight plaster
- 0.30 W/mk
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Approved Document L1B - Work in Existing Dwellings
As part of AD L1B work in existing dwellings, element values are used to determine compliance as SAP is not appropriate
Standards for thermal elements (W/m2K)
| Element |
Extensions |
Renovations |
| Wall |
0.30 |
0.35* |
| Floor |
0.22 |
0.25* |
| Roof |
0.16 ceiling |
0.16 ceiling |
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0.20 on pitch |
0.20 on pitch |
| Windows, roof lights, glazed doors |
1.80 or |
2.0 or |
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BFRC band D 1.2 centre pane |
BFRC band D 1.2 centre pane |
| Other doors |
3.0 |
3.0 |
*Where practicable the values for renovations are generally less stringent than those for extensions because physical details
of parts of the existing work (eg. floor levels) could make new-build U-values unrealistic, even impossible to achieve.