Net Zero Carbon Supplementary Planning Document

3. Policy NZC1

Achieving Net Zero Carbon Development

• Operational means only the carbon emitted during the in-use phase of the building;
• Regulated means only the share of those operational carbon emissions that are from an energy use that is regulated by Building Regulations, for example heating and hot water systems, or fixed lighting circuits.

Table 1: Summary of Policy NZC1 requirements by building type.

Meeting the requirements in proposals for 1 or more new dwellings

3.5 The required minimum on-site reduction is a 63% reduction in regulated carbon emissions compared to a baseline of Part L of the Building Regulations 2021.

3.6 For the avoidance of doubt, this is the Part L 2021 notional building baseline specification, which has a gas boiler. See Table 1.1 of Part L for dwellings² for a summary, or Table R1 Appendix R in SAP 10.2³ for the full baseline specification.

3.7 This required minimum 63% on-site carbon reduction on Part L 2021 is approximately equivalent to a 75% reduction on Part L 2013. This target reflects the Future Homes Standard⁴ (FHS).

3.8 Therefore, it is anticipated that most new residential developments will be able to meet the on-site minimum requirement of Policy NZC1 by meeting the notional building specification of the Future Homes Standard.

3.9 Compared to the Part L 2021 notional dwelling, the Future Homes Standard notional dwelling has the following improvements:

• Improving thermal insulation and resistance (U values) of floors, roofs, walls, doors and glazing (See Guidance for Policy NZC2(A) Section 4, Table 3)
   
• Including a heat pump as the primary heat source instead of a gas boiler (See Guidance for Policy NZC2B Section 5, Tables 7-8)

3.11 We note that it has already been proven feasible to deliver homes that perform at this standard in Warwick District – see GallowsHill case study. Commenced in 2020, this social housing project achieves a 77% improvement on Part L 2013 (which means it would meet or outperform the minimum on-site standard required by Policy NZC1). This was achieved through fabric improvements, air-source heat pumps, and solar panels.

3.12 Proposals are unlikely to be able to meet the required on-site improvement without a heat pump or similarly efficient and low carbon heat source.

– Proposals with gas boilers will not be considered acceptable. Nor will 'hydrogen-ready' gas boilers because there is not yet a credible, guaranteed time- bound source for the conversion of the gas grid to hydrogen, and at present the production of hydrogen either uses fossil fuel or uses several units of electricity to produce the equivalent unit of hydrogen energy.

– Proposals with direct electric heatingare unlikely to be able to achieve the required minimum on-site improvements unless significant further improvements are made to the fabric U-values and airtightness, and/or an extensive solar PV array.

Meeting the requirements in non-domestic developments

3.13 The required minimum on-site reduction is a 35% reduction in regulated carbon emissions compared to the baseline compliant development under Part L 2013, including the notional systems as determined by the final proposed building specification⁵.

3.14 It should be noted that Part L 2021 is now a minimum requirement and itself delivers a ~27% carbon improvement on Part L 2013. The minimum policy requirement of a 35% carbon reduction is therefore a small improvement on Part L 2021.

3.15 However, as all development during the DPD's lifespan will have to do calculations against more recent Part L baselines (2021 or later) for building control purposes, the Council will also accept proposals that demonstrate an on-site >35% reduction against a Part L 2021 baseline⁶. This will be afforded weight in favour, as the Council recognises that the 2021 baseline is already lower-carbon than the 2013 baseline.

3.16 The 35% reduction is expected to be achieved through a passively-led specification that improves on that of the Part L notional building.

3.17 According to the energy hierarchy, applicants should firstly pursue the requirement for energy efficiency specification to achieve a 19% (or greater) improvement on the 2013 building regulations by energy efficiency measures alone (as established separately in Policy NZC2(A)).

3.18 Selection of more efficient products is one way to achieve part of the required Part L regulated carbon reductions. For example, for a heat pump, the notional Coefficient of Performance (COP) performance values in Part L 2021⁷ are 2.86 seasonal generator efficiency for hot water and 2.64 seasonal system coefficient of performance for space heating (or in Part L 20138, these were 2.565 for hot water and 2.43 for space heating). Modern heat pump systems can significantly improve on these performance values through good design, system selection and commissioning For example, industry articles ^9,10,11 in 2023 reference 'average' efficiencies of 300% for air-source heat pumps (this would be a COP of 3), 350% for ground-source (a COP of 3.5) and 450% for water-source (a COP of 4.5). These articles also cite efficiencies of up to 500% or even 600% for the most advanced products on the market.

3.19 In general, it should be feasible to achieve most if not all of the required 35% improvement on 2013 TER primarily through a combination of fabric measures (e.g., insulation), other building services efficiencies (e.g., lighting and fittings), and use of modern heat systems with greater efficiencies (such as heat pumps).

3.20 As per the energy hierarchy, after initial priority is given to fabric and system measures to reduce energy demand, further progress in achieving or going beyond the 35% reduction can be made through maximising the installation of onsite renewable systems such as photovoltaic panels.

3.21 Table 2 summarises various carbon and energy saving measures and their potential contribution to the policy requirements of the NZC DPD.

Table 2: Carbon- and energy-saving measures categorised by their contribution to different parts of the policy requirements by development type

3.22 Applicants must submit within their Energy Statement (see also Pro Forma in Annex):

• The Target Emission Rate (TER) that represents the baseline (i.e., the emission rate of the notional building for Part L 2021 for dwellings, or either Part L 2013 or 2021 non-domestic development).
• The Dwelling Emission Rate (DER) or Building Emission Rate (BER) (as applicable to the proposal type) with all proposed improvements
• The % reduction on the TER that is achieved by this DER or BER (as applicable to the proposal type).
• The proposed building specification for all elements (U-values, airtightness, glazing ratio, heat recovery if applicable, lighting, ventilation, heating fuel, heating system, hot water system, cooling system if applicable, renewable energy, any other energy-using system efficiencies) laid out alongside that of Part L 2021 (or 2013 as applicable to your baseline), to demonstrate how your proposed improvement in carbon emissions has been achieved.
• Commentary on energy efficiency measures including passive measures such as solar gain and resulting energy efficiency improvements to fulfil the requirements of Policy NZC2(A) (see guidance in Section 4 of this SPD, pp. 20–31) including:
  • For non-residential applications, this should include confirmation of which of the proposed building element improvements are counted towards ‘improvement from energy efficiency measures’ as per the definition in guidance for Policy NZC2(A) and what % of TER reduction these deliver.
• For residential dwellings, the % improvement on Target Fabric Energy Efficiency.
• Commentary on proposed zero or low carbon energy sources their suitability and effectiveness for the development proposed and carbon emission reductions they impart to the design to comply with Policy NZC2(B) (Section 5, pp. 32-49) and achieve on site net zero regulated carbon.
• A calculation of the proposed development’s total annual residual emissions, showing your workings as the DER or BER multiplied by the amount of floor space created in each building typology.

A calculation of the required offsetting amount (tonnes of CO2, and £amount) as per the contribution calculation detailed in guidance for Policy NZC2(C) in Section 6, pp. 50–53.

3.23 The same carbon factors must be used for both the baseline and the proposed emissions rate (DER or BER) to ensure that the two indicators are comparable.

3.24 The carbon factors used should be those of the latest available version of Standard Assessment Procedure (SAP) or Simplified Building Energy Model (SBEM) (as applicable to building type) to ensure that these factors are as close as possible to the contemporary grid carbon factor (recognising that the electricity grid has been, and is expected to continue decarbonising).

3.25 All proposed building elements in the planning application energy statement (U-values, system efficiencies etc) should reflect the same specification that is separately submitted to and confirmed by Building Control.

3.26 For larger proposals (10+ homes) that consist of a small number of repeated home types, the calculation does not need to be repeated individually for every home but can instead present a sample of 20% of all homes including at least one of each home type¹², present within the development. The total development carbon emissions can then be calculated by multiplying these sample results up to reflect the full development area, with a weighted figure that represents the GIA created in each typology and orientation.

3.27 The calculations should be made and submitted at the following times:

• For Outline Planning applications: Applicants should identify the expected building specification in their Energy Statement and Pro- Forma.
• For Full Planning applications and Reserved Matters:Applicants' calculations in their Energy Statement and Pro-Forma must reflect the specified building design.
• For Section 73 applications: Applicant's calculations in their Energy Statement and Pro-Forma must reflect any changes to the specified building design.
• For discharge of conditions: Applicants must re-calculate and submit these figures on completion of the building, before occupation, using the actual as- built specification. Again, this must reflect any as-built information given to Building Control.

3.28 The as-built recalculation should capture and confirmany changes in building element specification or build quality that often arise in the construction process. It should be informed by:

• The measured air-permeability, tested in accordance with the procedures set out in CIBSE TM23 guidance, and reported as statutory compliance in Section 7 Part L. The air-tightness building control reports are to be included.
• The as-built Building Regulations England Part L (BREL) report produced for building control, containing photographs as specified in Appendix B of Approved Document Part L 2021.
• An infrared thermographic survey, if the building is completed within the central heating season (October to March).
• Any findings generated by the building control surveyorduring site inspections.
  
   

Measures towards enhancement of building quality and energy performance

3.29 In addition to the statutory checks required within Approved Document Part L 2021, it is recommended that applicants follow an accredited quality assurance process to ensure "as built" performance is as close to design predictions as possible. Passivhaus certification is one process which can assure build quality, alongside the Assured Performance Process from the Good Homes Alliance.

3.30 Evaluating building performance following occupancy is highly recommended to assess the effectiveness of design choices, and potentially address any commissioning or building design short comings. Applicants should consider using "BS40101 Building performance evaluation of occupied and operational buildings 2022" to guide the process of evaluating the performance of buildings in operation.

3.31 Developers will also be required, by way of a condition, to produce a home user guide for occupiers.

3.32 Where evidence can be provided within the application and/or discharge of conditions to show that any of the aforementioned quality assurance processes have been followed, this will be looked upon favourably as a measure towards enhanced credibility of the building's proposed performance.

3.3 Policy NZC1 also establishes that a certified Passivhaus building will also be considered to have complied with Policy NZC1 provided that it does not use on-site fossil fuels of any sort-

• To take this route to compliance with Policy NZC1, the applicant must submit Passive House Planning Package (PHPP) calculations to demonstrate compliance with NZC1.
• Applications would also then be required to submit the finished Passivhaus certification to the Council for discharge of conditions prior to occupation.
• Where a proposal includes one or more buildings that are Passivhaus certified, but also other new buildings that are not certified, the buildings that are not certified will still be subject to the standard route to compliance with Policy NZC1 and the subsequent energy hierarchy policies (NZC2A, B,C).

3.34 Passivhaus certification requires the achievement of certain stringent energy efficiency targets, including¹³:

• 15kWh/m2/year limit on space heating demand.
• 15kWh/m2/year limit on space cooling demand.
• 0.6 limit on air changes per hour (to help deliver the space heating and cooling limits noted above).
• 60kWh/m2/year limit on total energy use intensity (termed ‘primary energy renewable’).
• 135kWh/m2/year limit on total primary energy demand.

3.35 The above cited targets are for Passivhaus ‘Classic’. Optional enhanced Passivhaus certifications are also available (Plus and Premium) which require even tighter targets on total energy use intensity, and additional targets for renewable energy generation in kWh per square metre of building footprint.

3.36 The Passivhaus certification system requires that the above targets must use the calculation method ‘Passivhaus Planning Package’ (PHPP) which is a highly accurate method to predict a building’s energy use. The certification process also involves verifying certain performance parameters after completion of the building. As a result, Passivhaus buildings avoid the ‘performance gap’ and it is deemed that this certification represents such a significant improvement in actual on-site energy performance (compared to a building using the conventional building regulations energy calculations – see Figure 2.

3.37 Although Passivhaus Classic certification does not require the inclusion of any renewable energy on site and therefore would not be 'net zero carbon', the increased quality and effort involved in achieving this certification is regarded as sufficient to address the requirements of policy NZC1 and no further renewable energy or offsetting will be required for such development.

3.38 Proposals that further achieve Passivhaus Plus or Premium will be afforded significant weight in their favour as this represents not only the achievement of actual in-use energy performance to exemplary levels, but also the delivery of renewable energy to meet or exceed the home's energy demand (thus achieving true net zero operational carbon, or even becoming carbon negative in operation; see Figure 2).

3.39 Please note that even in a Passivhaus certified scheme, direct electric heating should still be avoided especially in dwellings, due to the probability of excessive energy bills and risk of fuel poverty. Although Passivhaus certification does not directly prohibit the use of direct electric heat, the Passivhaus Trust emphasises¹⁴ that the use of direct electric heat will make it difficult to achieve the Passivhaus required limit on primary energy demand.