Reduce Compliance Costs

Carbon Factors & SAP

Building regulations require CO₂ emissions of a new development, the ‘Dwelling Emission Rate’ (DER), to be below the ‘Target Emission Rate’ (TER), the emissions of a notional building of the same size and shape as the development; the target rate is set within the current Standard Assessment Procedure (SAP) in Part L of the Building Regulations.

As non-combustion systems, ground source heat pumps emit no point of use CO₂ emissions, nor any pollution for that matter.

Building regulations and SAP take into account the carbon intensity and emissions of what is powering the heating system, in ground source heat pumps case, electricity.

As a highly efficient form of heating – delivering 3-4kW of heat for every 1kW of electrical energy used to power the pump – ground source heat pumps offer an ultra-low carbon solution.

Just how ‘low-carbon’ a shared ground loop ground source heat pump system is compared to other heating alternatives is dependent on the carbon factors assumed for each energy source.

SAP2012 & SAP10 Comparisons

Currently carbon factors used in Part L are based on those in SAP2012.

Using the current electricity related carbon emissions in SAP2012 for electricity at 519gCO2/kWh, Kensa’s shared ground loop array ground source heat pump system operating at 320% efficiency produces a carbon saving of 36.9% compared to a gas combi boiler.

The proposed next version of SAP (SAP 10) – and already adopted by London – reduces the figure of electricity related carbon emissions to 233gCO2/kWh, similar to those of gas, due to the increasing decarbonisation of the electricity grid with clean, renewable energy sources such as wind and solar PV replacing the burning of coal.

Thanks to ground source heat pumps efficiencies, by more than halving the CO₂ emission factors for electricity in SAP10 the carbon saving for ground source compared to a gas combi boiler would be 70.9%.

Carbon Offset Funds

To achieve London’s zero carbon commitments by 2050, all new developments in London must achieve an on-site carbon reduction of at least 35% beyond the Target Emission Rate (TER). This percentage will increase over time in order to achieve the zero-carbon London ambition and reflect the cost of more efficient construction methods.

The new Draft London Plan goes a step further, stating 10% of the 35% target should be met through energy efficiency measures alone, encouraging a sensible fabric first approach.

As further impetus for ultra-efficient builds, any residual CO₂ emissions are to be offset and paid for by the developer at a suggested rate of £95/tonne, which is utilised by carbon offset funds for further energy efficiency improvements in London boroughs.

The impact of changing carbon factors means the cost to comply with emissions reduction targets increases for developers who traditionally specified gas, in particular gas CHP, whilst it becomes cheaper for those specifying heat pumps.

For developers in London using SAP10 figures and the Draft London Plan’s proposed minimum 10% fabric efficiency measures, the simplest and cheapest way to achieve carbon compliance is to specify a ground source heat pump alongside the minimum energy efficiency measure requirements. By simply coupling the 10% energy efficiency measure improvements with a ground source heat pump, a development’s emissions would be reduced by 74%, leaving just 26% to be offset.