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SAP 10: Changes to SAP Calculations and Energy Efficiency Requirements

Find out what SAP is and what changes have been made to the calculations and energy efficient requirements.

SAP 10: Changes to SAP Calculations and Energy Efficiency Requirements

SAP10 changes to energy efficiency calculations

UK government legislation stipulates that all new build domestic properties must have a Predicted Energy Assessment (PEA) and Energy Performance Certificate (EPC). These certificates are legal documents required as part of the Energy Performance of Buildings Directive.

Both the PEA and EPC are produced using Standard Assessment Procedure (SAP) calculations, which are also used for demonstrating building control compliance.

In 2018 the government announced the latest revision, SAP 10, would launch in 2019-2020, as a result of proposed changes to Approved Document Part L of the Building Regulations.

What is SAP?

SAP is the methodology used by the government to assess and compare the energy and environmental performance of dwellings. Its purpose is to provide the accurate and reliable assessment of dwelling energy performance needed to underpin energy and environmental policy.

SAP was developed by the Building Research Establishment (BRE) in 1992 as a tool to help the government deliver its energy efficiency policies. Ultimately SAP provides a standardised framework for calculating the energy consumption of dwellings. SAP is used extensively as a way of compliance with the Building Regulations.

For new build and, in other cases covered in L1B (material changes of use such as a barn to a dwelling; commercial premises to flats; or highly glazed extensions), SAP calculations are required and undertaken in two stages. Firstly, at the design stage (pre-construction) and also at the built stage.

SAP 10

Design Stage SAP & Predicted EPC

Before the start of building work, an SAP calculation should be carried out to demonstrate that the Dwelling Emission Rate will be no worse than the Target Emission Rate. The design stage SAP compliance document and a Predicted Energy Assessment (PEA) is provided on completion of the SAP calculations, which demonstrates to the building control body that the proposed dwelling should comply with the regulations.

Built Stage SAP & EPC

On completion of building work another SAP calculation, referred to as ‘As Built’ calculations, should be carried out, based on the actual building specifications, i.e. incorporating any specification changes from the design stage. The built stage SAP compliance document and an Energy Performance Certificate demonstrates to the building control body that the dwelling – as built – complies.

Upcoming changes – SAP 10

We received an informative presentation about changes to SAP and Approved Document Parts L1A and L1B of the Building Regulations, given by James Rivers, of Ashby Energy Assessors, with whom we partner when our clients require SAPs, EPCs, air leakage or acoustic tests.

James started by providing an overview of current requirements, from the SAP issued in 2012, and then outlined the main proposed updates to SAP calculations included in SAP 10.

The main changes that impact on building design are as follows:

Changes in fuel and CO2 factors

The CO2 emission factor for electricity will be reduced from 0.519 kgCO2/kWh to 0.233 kgCO2/kWh, making a change from gas to electric heating more feasible. Assessment under SAP 10 means it could be easier to achieve compliance with electric heating.

Thermal bridging recording (y-value)

The default used in the current SAP assessment will increase with the removal of Accredited Construction Details, meaning more construction details will possibly need modelling to enable more accurate values to be made available. This will give designers a better understanding of heat loss in a dwelling.

Hot water demand

The calculation of hot water demand will consider the number of showers and baths present in a dwelling, including flow rates, which will be used to calculate the volume of hot water required, resulting in a more accurate hot water assessment.

Thermal mass parameter

The current indicative options of low, medium and high for the thermal mass parameter will be removed from SAP 10. Therefore, all dwellings will be required to have a calculated thermal mass parameter based on their element areas and kappa values. The thermal mass parameters currently used are now judged to be too arbitrary to reflect a building’s actual performance.

Lighting efficiency

SAP 10 will be updated to reflect the changes in lighting technology and the efficiency of lamps that have moved at such a pace in the last decade. SAP 10 will record the amount and type of lamps in a dwelling. The more LED and compact fluorescent bulbs (the more efficient, more lumens per watt), the better the result obtained.

Please note the above points are not exclusive, and other important factors will be amended and included in the new SAP 10 assessment. However, it’s worth noting that until SAP 10 comes into force (and once Part L is updated), we need to continue to use SAP 2012 for Building Regulations compliance and EPCs.

It was an interesting and thought-provoking session and one the construction industry needs to understand and take on board, to provide improvement to existing and new dwellings that will be more energy and carbon-efficient as we build towards a zero-carbon future.


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