On 1 October 2010, the requirements of Part L of the Building Regulations changed to further improve the energy efficiency of new homes.  

The big change is that there is a 25% improvement required in the DER/TER calculation as compared to the 2006 Approved Document. The DER/TER calculation shows that the emissions of carbon dioxide due to energy uses in a new home are no greater than a theoretical government home of the same size and shape. The 25% reduction in CO₂ emissions equates to that required by Level 3 of the Code for Sustainable Homes. In England, with the exception of planning conditions and the construction of affordable homes where public money is funding them, compliance with the whole Code is not mandatory and the energy and carbon dioxide emissions sit alongside 33 other criteria.

The DER/TER calculation is based on data and algorithms contained within SAP 2009, which replaces SAP 2005.

With regard to the design, the only way to demonstrate overall compliance is based on the carbon dioxide emission rate.  There are 5 steps, the main one being:

To show that the emissions of carbon dioxide due to specified energy uses in new homes are no greater than a theoretical home of the same size and shape.  This is a fairly complicated calculation, which takes into account a number of factors including the built in thermal insulation, the heating system and its fuel and an assumption as to how airtight the completed home will be. 

The initial calculation showing that the design works from a CO2 emission point of view can then be sent to the building control body along with the Predicted Energy Assessment (PEA) as part of your application for Building Regulation approval.  The time to do the calculation is at the design stage (in fact it's a legal requirement).  Don't wait until you've started work because if the design doesn't stack up you've probably got a fairly major problem.

The calculation is usually done by an On Construction Domestic Energy Assessor (OCDEA), like us, operating under a quality assured scheme.  The benefit of this route is that whoever is checking for compliance with the Building Regulations need not delve any further to verify that the calculations are correct.

As part of the DER/TER calculation the use of Accredited Construction Details now plays a more significant part.  Briefly up to 25% of all heat loss is through junctions between external elements and components.  The detailing outlined in the Accredited Construction Details is of great importance and if you don't understand the implications of not following these details then you are heading for a fall. 

On small sites most new houses will require an Air Pressure Test at the end of the build to confirm that the assumption in the initial calculations are valid for the home(s) as built.  We have a list of businesses that can offer this service, and on our links page you can connect to the web-site of David Hicks (ITS Infra-Red) who is particularly helpful in this matter.

The Future

There are more changes in the pipeline for Part L1 A.  By 2016 the government's proposal is for all new homes to be zero carbon in terms of emissions from space, water heating and appliances although (at the time of writing) the exact definition has not yet been published. The next Part L1 A revision on the route to achieving this is proposed for 2013, when in addition to a 44% reduction in the CO₂ emissions, (as compared to the 2006 requirement) a Fabric Energy Efficiency Standard is likely to be introduced. This will specify the maximum energy use in terms of kWh/m²/year and the current proposal is that there will be two different figures depending upon the built form.

Please note a number of local authorities are putting conditions in planning consents requiring that new homes must meet a particular Code level.

Please read the planning conditions carefully. 

January 2011