2.1 The same approved calculation tool must be used to calculate the target primary energy rate, target emission rate and target fabric energy efficiency rate and the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate.

2.2 The dwelling primary energy rate, dwelling emission rate and dwelling energy efficiency rate must be calculated at both of the following points using the same calculation tool.

a. Before work starts, using design values.

b. When work is complete, using figures for the building as constructed, and incorporating both of the following.

i. Any changes that have been made during construction to the list of specifications.

ii. The measured air permeability.

2.3 At both of these points the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate must not exceed the target primary energy rate, target emission rate and target fabric energy efficiency rate, respectively. The specification of the actual dwelling may vary from that of the notional dwelling if the dwelling meets the target primary energy rate, target emission rate, target fabric energy efficiency rate and the guidance in this approved document.

Building control notification

2.4 The building control body must be notified, before the work starts, of all the following.

a. The target primary energy rate and the dwelling primary energy rate (calculated using design values).

b. The target emission rate and the dwelling emission rate (calculated using design values).

c. The target fabric energy efficiency rate and the dwelling fabric energy efficiency rate (calculated using design values).

d. A list of specifications used in the calculations.

Items (a) to (d) above may be reported using the design stage Building Regulations England Part L compliance report (BREL report). For further details of the design stage BREL report, see Appendix B.

2.5 The building control body must be notified, once the work is complete, of all of the following.

a. The as-built target primary energy rate and as-built dwelling primary energy rate.

b. The as-built target emission rate and as-built dwelling emission rate.

c. The as-built target fabric energy efficiency rate and as-built dwelling fabric energy efficiency rate.

d. A list of specifications used in the as-built calculations, and whether the specifications have changed from those used in the design stage calculations.

Building control bodies are authorised to accept notification of (a) to (d) above as reported in the completion stage BREL report together with photographic evidence of compliance. For further details of the post-completion BREL report and photographic evidence, see Appendix B.

Buildings that contain multiple dwellings

2.6 Buildings that contain more than one dwelling must comply with one of the following.

a. Every individual dwelling complies with all of the following conditions.

i. The dwelling primary energy rate must not exceed the individual dwelling’s target primary energy rate.

ii. The dwelling emission rate must not exceed the individual dwelling’s target emission rate.

iii. The dwelling fabric energy efficiency rate must not exceed the individual dwelling’s target fabric energy efficiency rate.

OR

b. All of the following are met.

i. The average dwelling primary energy rate for the whole building, calculated in accordance with paragraph 2.6, must not exceed the average target primary energy rate.

ii. The average dwelling emission rate for the whole building, calculated in accordance with paragraph 2.6, must not exceed the average target emission rate.

iii. The average dwelling fabric energy efficiency rate for the whole building, calculated in accordance with paragraph 2.6, must not exceed the average target fabric energy efficiency rate.

2.7 The average dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate are the floor-area-weighted averages of the individual dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate for all the dwellings in the building. The average dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate should be calculated using the same averaging methodology.

An average dwelling primary energy rate, dwelling emission rate or dwelling fabric energy efficiency rate should not be calculated across separate buildings on a site.

Guidance on how to calculate an average target primary energy rate is given in paragraph 1.5.

Guidance on how to calculate an average target emission rate and average target fabric energy efficiency rate is given in paragraph 1.6.

NOTE: Information and photographic evidence should be provided for each individual dwelling, as described in Section 9 and Appendix B.

Community heating systems and district heat networks

2.9 If thermal energy is supplied from a district heat network, a CO2 emission factor and primary energy factor for the heat delivered to the dwelling by the district heat network should be calculated. These factors should be used in the calculations of the dwelling primary energy rate and dwelling emission rate.

2.10 The same CO2 emission factors and primary energy factors used to calculate the dwelling emission rate and dwelling primary energy rate should be used to check against the minimum performance standards described in Section 6 of this approved document.

2.11 When calculating the dwelling primary energy rate and dwelling emission rate for a dwelling connected to a community heating system or district heat network, the following should all apply.

a. The annual percentage of heat supplied from each heat source should be the same for each newly connected dwelling.

b. The calculation should account for the predicted effect of all dwellings that will be connected to the system in the first 12 months after the dwellings are connected.

c. A submission to the building control body should be made to show that the community heating system or district heat network has the capacity to provide the percentage of heat that is assumed.

2.12 When calculating the dwelling primary energy rate and dwelling emission rate for a dwelling connected to a new district heat network, the calculation should include all heat sources to be used up to 31 December 2027. In this way, any planned transition of the heat network to an alternative means of heat generation will be properly accounted for. When there will be a change in heat source up to 31 December 2027, a submission to the building control body should be made to show both of the following.

a. That planning permission, if required, has been granted for the change.

b. That the heat network will connect to the new source, with confirmation in the form of a signed contract to connect and supply heat.

NOTE: When calculating the dwelling primary energy rate and dwelling emission rate for a dwelling connected to an existing district heat network the calculation should not include the effect of any change in heat sources after the dwellings are connected.

NOTE: An existing district heat network is defined in Appendix A. A new district heat network should be taken as meaning any other district heat network.

NOTE: New dwellings connecting to an existing district heat network should follow the standards in Section 6.

Swimming pool basins

2.13 When calculating the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate for a dwelling with a swimming pool, the thermal performance of the pool basin should not be included in the calculation. Instead, the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate should be calculated as if the area covered by the pool were replaced with the equivalent area of floor with the same U-value as the pool surround.

Party walls

2.14 When calculating the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate, a party wall U-value for the type of construction adopted should be applied as set out in Table 2.1.

general G6
Table 2.1 U-values for party walls

Internal lighting in the dwelling emission rate and dwelling primary energy rate calculations

2.15 The calculations for both the dwelling primary energy rate and dwelling emission rate should account for the efficacy of lamps installed in the fixed lighting locations.

Achieving the target primary energy rate, target emission rate and target fabric energy efficiency rate

2.16 Provided the dwelling satisfies the minimum standards for fabric elements set out in Section 4, the designer can achieve the target primary energy rate and the target emission rate by using any combination of the following.

a. Fabric energy efficiency.

b. Efficient building services.

c. Low and zero carbon technologies integrated in an appropriate mix.

2.17 The designer can achieve the target fabric energy efficiency rate only through fabric energy efficiency.

NOTE: To meet the target fabric energy efficiency rate, the energy efficiency of some elements will need to be significantly better than the minimum standards for fabric elements set out in Section 4.

Section 2: Calculating the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate