-:- Approved Document L2B -:-
Conservation of Fuel and Power in
Existing Buildings other than Dwellings
For building work on existing buildings that are not dwellings Part L2B of the Building Regulations should be used. An exception to this is where an extension is attached to an existing building, and the extension is greater than 25% of the existing buildings floor area and also over 100m2. In these situations the extension should be considered as a separate building and assessed using Part L2A. Regardless of what Part is sued to assess any extension there are times when the inclusion of an extension can force an improvement to the existing building energy efficiency, known as consequential improvements. This will only occur in the following circumstances:
- 1. The existing building has a floor area greater than 1000m2 before the extension is built.
- 2. The existing building has poor levels of thermal insulation.
- 3. The existing building has single glazed windows.
- 4. The heating, cooling and hot water systems within the existing building are 15 years old.
- 5. The lighting system within the existing building was installed before 1992.
The thrust of consequential improvements is to improve the energy performance of the worst performing buildings that are currently in use. As a result building work to most modern buildings would not trigger any improvements to the existing building. Should improvements be required then the value of the improvements should be equal to 10% of the build cost of the extension.
The introduction of new heating or cooling systems into existing buildings can trigger consequential improvements to the existing buildings walls, floors and roof (Thermal Elements). Again this would only be applicable if the existing building was greater than 1000m2 and the existing thermal elements were poorly insulated. Any improvements required would be limited to the areas served by the new heating of cooling systems.
Renovation and repair of thermal elements is now included within the building regulations and when carrying out renovation work to poorly insulted thermal elements then insulation should be introduced. This work would include re-roofing a slate roof, re-felting a flat roof, replacing a timber floor with a concrete floor and rendering a wall.
All the improvement work to existing building should be economically feasible and this is shown by the improvement work having a 15 year payback period. Any work that can be shown to achieve a payback of greater than 15 years would not have to be completed.
Gladwood (BCS) Ltd can produce the Carbon Dioxide Emission calculations using IES Virtual Environment or iSBEM software on extensions if they area required. We can produce schedules and simple payback calculations to limit the improvement works required to existing buildings and produce L2B compliance reports that explain the building work that is being undertaken and identify how the regulations are being complied with.
