Part L of the building regulations sets Target Emissions Rate (TER) based on CO2 emissions for all types of buildings. The target uses a “notional” building design and sets “improvement factors” for the developer to demonstrate that their designs are within the targets. The latest 2010 edition uses the 2006 level with an improvement factor of around 25%. By definition the TER remains the same for a given building. The Dwelling Emissions Rate or Building Emissions Rate, for non-domestic situations, is dependent on the factors listed in section 14.3.
The DER & BER are building specific – therefore two “identical” buildings can have different emissions rates. An example of this would be two “identical” houses, one facing north the other facing south – the solar heat gains through the windows would alter the heating demand of the house. Another more significant difference would be if one of the houses were heated using mains gas and the other used heating oil as the fuel, this would alter the energy costs and carbon emissions. There are thousands of connotations for the differences; therefore it is impossible to give an energy demand figure for say a “typical” apartment, bungalow, workshop, hotel, school etc. Each building needs to be modelled individually using SAP or SBEM.
As with most regulatory systems, the devil is in the detail and with Part L (2010) at first glance the amendments do not seem too complicated. However, it should be borne in mind that the methodologies for the SAP and SBEM have also been amended to coincide with the changes to the regulations and it is the changes to the data and algorithms where designers will notice a further tightening of the requirements. To ensure that buildings are within the Part L targets, the construction details need to be more accurate, the building services equipment needs to be more efficient, the controls need to be more effective and commissioned more thoroughly. When all of these improvements are realised, it will be more common for renewable technologies to be required to make up the shortfall in the designs to achieve the 2010 Target Emissions Rates especially for buildings that are not using mains gas as the main heating fuel.