New Part L2 regulations came into force on May 6th 2006 and apply to non-domestic buildings beginning construction after this date. The regulations requiring designers to demonstrate significant reductions in carbon emissions from building energy use relative to the standards set by the previous (2002) edition of the regulations. This is achieved by performing a detailed analysis of the carbon emissions of two buildings:
The actual building – the building as designed, but subject to standard patterns of occupancy and plant operation, and
The notional building – a version of the building that conforms to standards similar to those applying in the Part L2 (2002) Elemental Method. The notional building is subject to the same occupancy and plant operation patterns as the actual building.
The analysis must demonstrate that the actual building’s carbon emissions improve on those of the notional building by a specified margin – 28% for an air conditioned building. It is this improvement that constitutes the tightening of the regulations in the 2006 edition.
The analysis of carbon emissions must be performed with accredited software applying the National Calculation Methodology (NCM), such as <VE> Compliance or BRE’s iSBEM program.
By contrast with the 2002 regulations, where a choice of three compliance routes was offered, the 2006 regulations stipulate a single compliance procedure. This has much in common with the Carbon Emissions Calculation Method (CECM) of the 2002 regulations, but there are important differences including the following:
The actual building’s performance must not merely match, but significantly improve on that of the notional building.
Assessments must be performed under standard occupancy and plant operating conditions. This means that under the new regulations, some of the data entered by the user to model the building for design work has to be replaced by different data for the purpose of compliance analysis.
Requirements on the control of summertime solar gains apply to the actual, not the notional building, and only to rooms without mechanical cooling. In this respect the 2006 notional building sets a slightly less demanding performance target than the 2002 notional building.
In terms of analysis methodology, the most significant change with respect to the 2002 Carbon Emissions Calculation Method is the requirement for standard occupancy and plant operating conditions. The consequence of this is that, in addition to the actual and notional buildings, the designer will usually need to model and analyse (for design and other non-regulations purposes) a third building:
The real building – this is the building as designed, and with the occupancy and plant operation conditions expected to apply in reality, rather than the standard conditions stipulated for Part L2 compliance.
The real building is the building presented in Apache View, where the special conditions required for Part L2 (2006) do not apply.
The testing of carbon emissions constitutes Criterion 1 of Part L2. The full set of criteria is as follows:
Criterion 1 – Achieving an acceptable building CO2 emission rate (BER).
Criterion 2 – Limits on design flexibility: this sets minimum standards for building fabric and system performance.
Criterion 3 – Limiting the effects of solar gains in summer: this imposes limitations on solar gains and temperatures in those parts of the building that are not provided with comfort cooling systems
Criterion 4 – Quality of construction and commissioning: this lays down requirements that the building must meet after construction. (Not covered by <VE> Compliance.).
Criterion 5 – Providing information: certain information must be provided to the owners of the building. (Not covered by <VE> Compliance.).
Users of the <VE> Compliance software are strongly advised to study the official documents defining the regulations.
