Impact of New draft SAPs (Part L) on future Energy Strategy Reports

The new draft Standard Assessment Procedure (SAP10) was published in July and here our Energy Services Director Umer Uzair reviews the impact of this on future Energy Strategy Reports.

Before we discuss the changes within SAPs, I would like to mention the purpose of SAP calculations and what is SAP? SAP is the standard assessment method to estimate the environmental performance of new homes to ensure that the development meets planning policy and building regulations.

The assessment is based upon the standardised assumptions according to BRE’s research for different occupant behaviours and how different types of families and individuals use their living spaces. The calculations take into account the building fabric, location, type of heating and hot water systems, lighting and the type of ventilation system. SAP is generally used to assess the energy and carbon performance of a building based upon the Building Regulations Approved Document Part L in domestic buildings.

One of the major changes in the draft SAP 10 is the change of fuel carbon factors and reduction in electric based carbon factor from 0.519kgCO2/kWh to 0.233kgCO2/kWh. Whilst in comparison the mains natural gas carbon factor hasn’t changed much i.e. the SAP 2012 has 0.216 kgCO2/kWh and the draft SAP 10 states 0.210 kgCO2/kWh. This changed means that now a house which runs on mains electrics has similar carbon emissions to one run on mains gas. However, it mentioned in the draft document that the method to derive the CO2 emission, primary energy and fuel prices factors are unchanged except the fuel prices to electricity which has been reduced due to the electricity wholesale prices.

The other interesting change is the change in default heat pump efficiencies: the additional design flow (heat emitter) temperature options have been provided for heat pumps and condensing boilers have been updated. The lower factor means that developments with heat pumps only has to be a minimum of over 100% efficient (current SAP 2012 has 170% as the default for Air Source Heat Pump) in order for it to be better than the gas based system. This would mean that the energy choices we currently have will be very different to what we can have under future regulations.

Also at present due to the higher carbon factor for an electrics based system, the gas boiler is still a favourable option for many developments. Whilst this change will help bridge the gap between decarbonisation and an electric system, it would however still be costly to run the domestic property on an electric-based system.

Here is the list of proposed changes as per the draft document published by BRE…. ( )

CO2 emission factors, primary energy factors and fuel prices, have been updated using the latest data available. The method to derive them is unchanged from SAP 2012 except for the fuel price attributed to electricity exported to the grid, which has been reduced to the electricity wholesale price.

The assumed heating pattern has been changed to a consistent daily pattern for all days of the week – previously a different pattern was used at the weekend.

Additional design flow (heat emitter) temperature options have been provided for heat pumps and condensing boilers, which affect their efficiencies.

Default heat pump efficiencies have been updated.

Default distribution loss factors associated with heat networks have been increased.

The calculation of lighting energy has been updated to allow recognition of new lighting types with higher efficacy.

The options for entering heat losses from thermal bridges have been revised.

An additional thermal bridge type has been added for junctions in roof-rooms which don’t fit any of the existing

The calculation of hot water consumption has been adjusted to account for shower flow rate.

The treatment of mechanical ventilation system heat recovery and aerodynamic performance has been revised.

The default efficiencies of some solid fuel heating appliances have been updated.

The air flow rates associated with chimneys and flues have been revised.

SAP 2012 used a fixed assumption for the proportion of electrical energy generated by Photovoltaic (PV) systems which is consumed within the dwelling. This has been replaced by a formula which also includes recognition of the presence of battery storage.

The impact of PV diverters2 is now taken into account.

An option to allow the overshading factor used for the PV calculation to be taken from Microgeneration Certification Scheme data has been added.

The assessment of summer internal temperatures has been refined and the blind/curtain use factor has been revised.

The air-conditioning efficiency (‘SEER’) table has been updated. T

The treatment of heat losses from heat interface units (used with heat networks) has been adjusted.

The Energy Strategy Reports (ESR) we produce, also known as Energy Assessments, Sustainability Statements or Energy Statements, prove that climate change mitigation measures are integral to your scheme’s design and evolution, and right for the context of the development.

Each of these mandatory energy assessments must prove how the targets for regulated CO2 emission reduction will be met.

At Syntegra, our energy strategy consultants work closely with you to satisfy the requirements of your development’s local authority, and show to planners that your project will meet planning policy energy and emissions criteria.

The Syntegra Group’s energy strategy consultants focus on specific areas when assessing your development’s energy usage and preparing your energy strategy reports. These include your scheme’s energy demands, energy saving measures and distribution, renewable energy generation, local authority sustainability checklists and Building Regulations Part L Compliance

For any future advice related to domestic or non domestic Energy Strategy Reports/Energy Statements please contact our dedicated Energy Team: or Umer Uzair: