SAP Ratings

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The new Part L1 Conservation of Fuel and Power in new dwellings Building Regulations came into force April 2006. To fall in line with the EU Energy Performance in Buildings Directive the new L1 document requires a major change in the way dwellings are to be assessed for compliance with energy efficiency and carbon emission standards.

Part L1 divides into five separate criteria to be met, noting that some of the criteria are interdependent with each other:

Criterion 1 – Achieving the TER
Criterion 2 – Limits on Design Flexibility
Criterion 3 – Limiting the Effects of Solar Gains in summer
Criterion 4 – Quality of Construction and Commissioning
Criterion 5 – Providing Information (for the building operator)

Criterion one requires the proposed dwelling to be modelled and simulated using an accredited software tool to evaluate the carbon emission from a “notional dwelling”, of the same geometry and function as the actual dwelling. An improvement factor is then applied to establish a target emission rate (TER) against which the actual design Dwelling Emission Rate (DER) must equal or better. To fulfil the requirements of this assessment, HRS utilise Elmhurst software. Assessments are carried out by consultants who are registered as “competent persons”.

SAP Ratings for Domestic Buildings to achieve Building Regulations Part L compliance

It is estimated that energy use within dwellings in the UK currently account for 27% of national carbon dioxide emissions. The 2006 revision of the Part L1A Building Regulations stipulated a 20% improvement factor over 2002 standards for the energy performance of new dwellings. This should be assessed at design stage by comparing the proposed new build with a notional building of the same geometry and form. The parameters for the notional building are that it must meet all the minimum requirement parameters of the 2002 Part L1A.

Total carbon dioxide emissions are calculated using information from architectural drawing, input data for the envelope fabric properties, heating, ventilation and lighting systems within the dwelling. The emissions for the notional building are expressed in kilograms of carbon dioxide per metre squared of useful floor area per year. The 20% improvement factor is then applied to this figure to calculate the Target Emission Rate (TER) for the proposed building. The figure for the actual dwelling as designed (DER) must be equal to, or less than this figure to achieve compliance with Building Regulations. As the dwelling approaches completion some commissioning testing e.g. pressurisation testing will be carried out and figures for the actual as built dwelling must also be incorporated into the calculation. Any alterations to the design during construction must also be reflected in the as built carbon emissions calculations.

The Part L1 Regulations are due to be revised in 2010. It is highly likely that a more stringent improvement factor will be introduced for all new dwellings. There is also a government commitment for all new dwellings to produce zero carbon emissions by 2016. It is therefore essential that serious consideration is given not only for current designs to meet immediate requirements, but strategies in place to fulfil the sustainability agenda of the UK.

Calculations carried out for Building Regulations compliance also form the basis of the calculations for an Energy Performance Certificate. This can only be produced by an accredited consultant on CLG approved software. Unlike the Building Regulations stipulations there is no minimum performance requirement specified by the EPC. The certificate will merely highlight the potential performance of the dwelling as designed and how this compares with others within the national stock.

SAP - Required Information Check Sheet