Part L2A SBEM Calculations

A new revision of Part L (Conservation of Fuel & Power) of the Building Regulations came into force in April 2006. The regulations relating to non-domestic buildings are in two parts:

Part L2A Conservation of Fuel and Power in New Buildings other than Dwellings

Part L2B Conservation of Fuel and Power in Existing Buildings other than Dwellings

At the design stage, the predicted energy performance of the building design is required by the Building Control Body or Approved Inspector at the time to support the submission of the Building Control Application.

At the as-built stage, once the building is completed, a further SBEM calculation confirms that the building meets the required standards for Part L, and a certificate is produced for submission to the Building Inspector.

Compliance with Part L2A can only be demonstrated using the National Calculation Methodology (NCM): Dimension 9 adopts the use of the approved SBEM software.

The NCM compares the total energy consumption of the building and its services, expressed as carbon dioxide emissions of the building, (“Building Emission Rate” or BER), with a target value (“Target Emissions Rate” or TER), derived from calculations for a “notional building”, which is similar in size, shape and class of use for the evaluated building.

The “Target Emissions Rate” requires an improvement factor to be applied to the notional building’s emissions according to the building services strategy to be used, ranging between 23% for naturally ventilated buildings to 28% for mechanically ventilated and air conditioned buildings.

In addition to this overall energy consumption requirement, minimum thresholds are set for Thermal performance of individual fabric elements, Building services plant efficiencies and Envelope air tightness.

Provision is made for credits to encourage the use of Low and Zero Carbon (LZC) technologies, and there is a further requirement to include means to limit solar gains in summer.

All buildings are subject to air tightness testing to demonstrate that the assumptions used in the energy calculations have been achieved in practice.

Building Control also now require verification, post construction, that metering is installed, building services are fully commissioned and a building Log Book has been prepared to provide the building owner with relevant information to enable him to operate his building effectively.

For further information or advice on Part L2 and SBEM Calculations please contact DIMENSION 9 on +44 (0) 845 459 7869 or on