Nigel Potter looks at what the toughened-up Part L, which is set to be implemented early next year, has in store for designers and contractors

Two years ago, the government pledged to toughen up the regulations relating to the conservation of fuel and power by 2005. It will fail to do this. Even though the start date for the revised version of Part L of the Building Regulations, 1 January 2006, misses this pledge by just one day, in reality Part L is unlikely to be enforced until April next year. The approved documents are not set to be published until this autumn and the industry is usually given six months between this date and enforcement.

The reason that the government has given the start date as 1 January is all to do with the European Union’s Energy Performance of Buildings Directive (see page 17). This directive requires EU member states to have a methodology in place by 4 January 2006 for calculating the energy performance of buildings. This must be based on every element that might affect it, whether it be fabric heat loss, daylight calculations, internal lighting efficiency, airtightness of the envelope, or heating and ventilation system type and efficiency.

The energy calculation procedures of Part L, which are contained in the documents SAP 2005 for dwellings and SBEM for non-domestic buildings (see page 15), are the means by which the UK government intends to meet this requirement. SAP is the government’s recommended system for the energy rating of dwellings, and the Simplified Building Energy Method is the method used to work out the energy performance of non-dwellings. The underlying object of these procedures is to reduce the overall energy consumption as measured by the total annual CO2 emissions (kg/m2 of gross floor area). For non-domestic buildings, the proposal is to reduce the energy consumption by 20% for air-conditioned and mechanically ventilated buildings and 15% for naturally ventilated buildings. There is also a proposal for non-domestic buildings to contribute 10% of their energy from renewable sources. In most non-domestic buildings the energy used needs to be 28% lower than the requirements of the 2002 edition of the Building Regulations. If the 28% reduction is not met, building elements, systems or airtightness will need to be changed. Targets laid out for new non-domestic buildings also include a maximum U-value target of 0.35 W/m2K for walls and 0.25 W/m2K for roofs (see “Part L targets”).

Achieving the requirement of providing 10% of energy from renewable sources will be challenging, particularly if a reasonable payback is required. Designers will need to address and cost options such as solar heating (evacuated tube) systems, solar photovoltaic cells, heat pumps, combined heat and power systems, wind generators, light pipes, phase change storage, and so on.

It will require a much more multidisciplinary approach to design than currently exists

The energy performance of the proposed building needs to be demonstrated before construction. Then, before the building is handed over, all of the parameters as installed and tested need to be input to the National Calculation Methodology. The building must attain the required carbon emission target, according to this method, before Building Control will be satisfied.

All of the above will require a different culture within the industry, as there will need to be an integration of the building services elements with the architect’s basic building design. Buildings should be designed, for example, on the basis that 28°C is not exceeded (in office spaces) for more than 20 hours a year. This requires a much more multidisciplinary approach to building design than currently exists.

The government is serious about climate change and our need to save energy. Mandatory building log books and energy metering will increase energy efficiency in building. There will also be another revision of the Building Regulations in five years’ time, as well as second tier documentation, which can be altered at any time without changing the regulations themselves. Everyone in construction will have to take note.

An enabling act

The latest revision to Part L will be much more far-reaching that its predecessor, thanks to a key piece of legislation introduced last autumn. The Sustainable and Secure Buildings Act allows Building Regulations to be used to improve the energy performance of existing buildings and to address the operational performance of buildings.

The Part L proposal to force householders to improve the energy efficiency of their homes if they spend more than £8000 on improvements is a consequence of the act. It means that the government can begin to tackle the energy performance of the 24 million existing homes as well as the 180,000 new dwellings built every year. The ODPM has yet to decide whether it will carry through this proposal to the approved documents. Although some in government regard it as a vital tool to reduce CO2 in existing housing stock, others fear that the extra cost – up to 10% of the improvement bill – will deter people from making any changes to their homes at all.

The Sustainable and Secure Buildings Act also allows Building Regulations to extend the requirement for regular reporting of the energy performance of buildings. This is essential to comply with the Energy Performance of Buildings Directive (see page 17). For example, the EPBD requires that inspections take place of air conditioning systems with a rated output of more than 12 kW of cooling.

Another power that the government has as a result of the act is to include embodied energy in future reviews of Part L. This means that the energy used to manufacture steel radiators, for example, could have to be included in carbon emission calculations for buildings.

The act also allows other elements of sustainability to be introduced into the Building Regulations, such as standards on water use, waste and use of materials.

part l targets

New buildings other than dwellings
Maximum U-values in draft approved documents (W/m2 K): n Walls 0.35

  • Roofs 0.25
  • Windows and rooflights 2.2
  • Doors 2.2n
  • Roof ventilators 6.0
  • Floors 0.25
  • Maximum area of 20% for rooflights
  • Maximum permitted airtightness of 10 m3/h/m2
  • 80% minimum seasonal efficiency of boilers
  • Not less than 45 luminaire-lumens/circuit-watt minimum lighting efficiencies
  • Maximum specific fan power for mechanical ventilation systems between 0.8 W/litre/s, for fan coils, and 2.5 W/litre/s, for central HVAC with heat recovery

New dwellings
Maximum U-values in consultation document for dwellings (W/m2 K):

  • Wall 0.35
  • Floor 0.25
  • Roof 0.25
  • Windows, doors and rooflights 2.2
  • Maximum permitted airtightness in naturally ventilated dwelling of 10 m3/h/m2
  • Maximum permitted airtightness in dwelling with balanced whole-house ventilation of 5 m3/h/m2
  • Maximum area of 20% of the roof for rooflights