Publication - Research and analysis

Building regulations - new non-domestic buildings - modelling of proposed energy improvements: research report

Research to identify potential improvements in energy and emissions performance for new non-domestic buildings. Produced in support of proposed improvements to energy standards for new buildings within Scottish building regulations in 2021.

Building regulations - new non-domestic buildings - modelling of proposed energy improvements: research report
Task 3: Modelling Options for a New Notional Building Specification

Task 3: Modelling Options for a New Notional Building Specification

1.10 Modelling of national profile to improved standards

140. This section assesses the impact of the improved notional buildings determined in the >1.1revious section. The improved standards are applied to the twelve sample buildings identified in Task 1 to reflect the national build mix and the change in benefits and costs are evaluated.

141. The current (2015) Section 6 notional building U-value specification is different for buildings that are naturally ventilated rather than mechanically ventilated or cooled; these differences are set out in Table 33. Similarly, the notional building air tightness value varies in response to the building floor area and whether the activity type is classified as side-lit, top-lit or no-lit. The proposals for the next revision to Section 6 are seeking to simplify as well as tighten the requirements and so it is proposed that this variation between different servicing strategies, floor areas and activity types should be removed. Therefore, the proposed low, medium and high fabric specifications set out in Table 33 apply across all building types regardless of servicing strategy, floor area and activity type.

1.10.1 SBEM Modelling Results

142. The twelve building sub-types set out in Table 62 were modelled using SBEM v5.6a for both the fossil (gas) and non-fossil (ASHP) for all three levels of specifications set out in Table 33 (low, medium and high). A summary of the cases modelled for each building type is set out below:

  • Gas + PV + Low building fabric and services improvements
  • Gas + PV + Medium building fabric and services improvements
  • Gas + PV + High building fabric and services improvements
  • ASHP + Low building fabric and services improvements
  • ASHP + Medium building fabric and services improvements
  • ASHP + High building fabric and services improvements

143. Key results from the modelling are set out in Table 36 to Table 47. The columns show the BPE and BER calculated using SBEM v5.6a with the proposed carbon emission and primary energy factors shown in Table 14 and Table 15. These are compared to the equivalent results for the 2015 compliant base cases previously presented in section 1.5.5. An adjustment has been applied to the DHW demand in primary schools to reflect the proposed changes to the NCM Activity Database for this building type. BPE is shown first here as this is proposed to be the main target metric.

144. Two of the twelve sample buildings use an electric ASHP as the base case heating scenario. For these two building the results for the three gas-heated options, listed above, have been omitted as not necessary for the analysis.

Table 36: Deep-plan Office, AC, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 69.6 0% 7.5 0%
Gas+PV Low 54.3 22% 6.0 20%
Gas+PV Medium 43.7 37% 4.9 34%
Gas+PV High 39.2 44% 4.1 45%
ASHP Low 58.6 16% 5.4 28%
ASHP Medium 53.9 22% 5.0 34%
ASHP High 52.5 25% 4.8 36%
Table 37: Deep-plan Office, AC, electric ASHP heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 67.7 0% 6.2 0%
Gas+PV Low NA NA NA NA
Gas+PV Medium NA NA NA NA
Gas+PV High NA NA NA NA
ASHP Low 58.6 13% 5.4 14%
ASHP Medium 53.9 20% 5.0 20%
ASHP High 52.5 23% 4.8 23%
Table 38: Hospital, naturally ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 159.4 0% 24.5 0%
Gas+PV Low 124.2 22% 21.7 12%
Gas+PV Medium 112.1 30% 20.4 17%
Gas+PV High 105.7 34% 19.2 22%
ASHP Low 73.5 54% 6.9 72%
ASHP Medium 69.7 56% 6.5 74%
ASHP High 64.5 60% 6.0 76%
Table 39: Hotel, naturally ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 371.0 0% 66.9 0%
Gas+PV Low 357.0 4% 65.0 3%
Gas+PV Medium 348.7 6% 64.4 4%
Gas+PV High 323.8 13% 59.8 11%
ASHP Low 182.3 51% 17.0 75%
ASHP Medium 176.7 52% 16.4 75%
ASHP High 158.1 57% 14.7 78%
Table 40: Hotel, AC, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 357.8 0% 58.2 0%
Gas+PV Low 358.7 0% 58.1 0%
Gas+PV Medium 335.7 6% 55.9 4%
Gas+PV High 316.4 12% 52.4 10%
ASHP Low 230.5 36% 21.2 64%
ASHP Medium 215.9 40% 19.9 66%
ASHP High 200.7 44% 18.4 68%
Table 41: Primary School, naturally ventilated, biomass heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 59.8 0% 2.5 0%
Gas+PV Low 48.5 19% 8.1 -225%
Gas+PV Medium 36.0 40% 6.8 -174%
Gas+PV High 30.2 50% 5.7 -130%
ASHP Low 35.8 40% 3.4 -35%
ASHP Medium 33.8 44% 3.2 -27%
ASHP High 31.0 48% 2.9 -16%
Table 42: Primary School, mechanically ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 39.5 0% 5.8 0%
Gas+PV Low 40.4 -2% 6.1 -5%
Gas+PV Medium 27.4 31% 4.7 19%
Gas+PV High 21.6 45% 3.6 38%
ASHP Low 36.4 8% 3.4 41%
ASHP Medium 34.9 12% 3.3 44%
ASHP High 32.5 18% 3.0 48%
Table 43: Primary School, naturally ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 51.7 0% 8.2 0%
Gas+PV Low 48.5 6% 8.1 1%
Gas+PV Medium 36.1 30% 6.8 16%
Gas+PV High 30.2 42% 5.7 30%
ASHP Low 35.8 31% 3.4 59%
ASHP Medium 33.8 34% 3.2 61%
ASHP High 31.0 40% 2.9 65%
Table 44: Retail Unit, AC, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 187.4 0% 18.3 0%
Gas+PV Low 109.8 41% 11.4 38%
Gas+PV Medium 91.7 51% 9.5 48%
Gas+PV High 88.0 53% 8.9 52%
ASHP Low 111.7 40% 10.2 44%
ASHP Medium 106.0 43% 9.7 47%
ASHP High 104.1 44% 9.5 48%
Table 45: Retail Unit, AC, electric ASHP heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 184.0 0% 16.9 0%
Gas+PV Low NA NA NA NA
Gas+PV Medium NA NA NA NA
Gas+PV High NA NA NA NA
ASHP Low 111.9 39% 10.2 39%
ASHP Medium 106.1 42% 9.7 42%
ASHP High 104.2 43% 9.5 43%
Table 46: Shallow-plan Office, naturally ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 61.0 0% 9.4 0%
Gas+PV Low 49.1 20% 8.1 13%
Gas+PV Medium 37.9 38% 7.1 25%
Gas+PV High 26.8 56% 5.0 47%
ASHP Low 36.2 41% 3.4 64%
ASHP Medium 34.3 44% 3.2 66%
ASHP High 30.1 51% 2.8 70%
Table 47: Distribution Warehouse, naturally ventilated, gas heating base case modelled CO2 emissions rates and primary energy values
Model Name Primary Energy, BPE Primary Energy, Margin CO2, BER CO2, Margin
2015 compliant 135.9 0% 23.5 0%
Gas+PV Low 131.6 3% 23.3 1%
Gas+PV Medium 112.3 17% 20.8 12%
Gas+PV High 98.8 27% 18.2 22%
ASHP Low 94.7 30% 9.0 62%
ASHP Medium 83.2 39% 7.9 67%
ASHP High 73.7 46% 7.0 70%

145. Further results from the modelling of potential 2021 standards are set out in Table 48 to Table 59. The tables show energy consumption by end-use, and energy generation from onsite PV (where applicable) as calculated using the SBEM v5.6a methodology. Again, these results are compared to the equivalent results for the 2015 compliant base cases.

146. There are several features in these results which may not be immediately intuitive; these are explained here:

  • There are many cases where the heating demand of the “2015 compliant” case is lower than one or more of the subsequent options. This is primarily due to the large improvement in lighting efficacy which results in lower internal heat gains and thus an increased heating demand.
  • In some cases (e.g. the office buildings), the DHW demand remains the same across all six of the assessed options. This is in cases where the DHW demand is entirely on the “low” demand system type as described from Paragraph 134 onwards. In these cases, the DHW system uses electric point-of-use heated across all the Gas+PV and ASHP options.
  • In some cases, the lighting energy for the two “Low” options is slightly lower than the “Medium” and “High”. The lighting efficacy is the same across all of these options. However, the G-value of the glazing reduces slightly for the “Medium” and “High” options, so the benefit of daylight-sensing controls is slightly reduced. In most cases this difference is too small to be shown in the rounded values in these tables.
  • The auxiliary energy demand of the “2015 compliant” case is sometimes lower than those of the subsequent six options. This is primarily caused by a switch to centralised DHW which includes a secondary circulation pump.

147. Table 51 and Table 52 show the results for the naturally ventilated and air-conditioned hotels. Comparing these two tables, the heating demand for the naturally ventilated hotel is much higher than that of the air-conditioned hotel. This shows the benefit of the heat recovery which is included in the air-conditioned scenario. The auxiliary demand is lower for the naturally ventilated hotel because it needs no fans for ventilation, so the small auxiliary demand is associated solely with the heating circulation pumps. Examining these two differences together it can be seen that the total energy demand for the ASHP options are lower for the naturally ventilated hotel. This shows that when the heating is very efficient (e.g. through the use of an ASHP) it can be better to accept a higher heat demand by omitting mechanical ventilation with heat recovery because the associated increase in auxiliary energy can be greater than the savings achieved by the heat recovery.

148. Table 59 shows the result for the distribution warehouse; this shows a substantial increase in the auxiliary energy demand for the three ASHP options. The reason for this increase is that the base-case gas heating system for the main warehouse area is a direct gas-fired radiant system. This system type is not compatible with an ASHP so the three ASHP options include a change to a wet heating system. The distribution warehouse is the only sample building where this occurs.

Table 48: Deep-plan Office, AC, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux Lighting DHW Total PV gen. Total minus gen.
2015 compliant 7.2 8.5 16.7 18.5 3.1 54.0 5.4 48.6
Gas+PV Low 9.4 5.6 16.5 11.5 2.6 45.6 7.4 38.2
Gas+PV Medium 8.4 4.2 15.2 11.6 2.6 42.0 11.2 30.8
Gas+PV High 4.2 4.4 15.2 11.6 2.6 38.0 11.2 26.7
ASHP Low 2.5 5.6 16.5 11.5 2.6 38.7 0.0 38.7
ASHP Medium 1.9 4.2 15.2 11.6 2.6 35.6 0.0 35.6
ASHP High 0.9 4.4 15.2 11.6 2.6 34.7 0.0 34.7
Table 49: Deep-plan Office, AC, electric ASHP heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux Lighting DHW Total PV gen. Total minus gen.
2015 compliant 1.6 8.8 16.8 20.1 2.8 50.1 5.4 44.7
Gas+PV Low NA NA NA NA NA NA NA NA
Gas+PV Medium NA NA NA NA NA NA NA NA
Gas+PV High NA NA NA NA NA NA NA NA
ASHP Low 2.5 5.6 16.5 11.5 2.6 38.7 0.0 38.7
ASHP Medium 1.9 4.2 15.2 11.6 2.6 35.6 0.0 35.6
ASHP High 0.9 4.4 15.2 11.6 2.6 34.7 0.0 34.7
Table 50: Hospital, naturally ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 50.8 0.0 3.0 33.3 41.8 129.0 0.0 129.0
Gas+PV Low 55.7 0.0 3.1 14.4 40.9 114.1 7.7 106.4
Gas+PV Medium 54.0 0.0 3.1 14.5 40.9 112.5 14.6 97.9
Gas+PV High 48.3 0.0 3.1 14.5 40.9 106.7 14.6 92.1
ASHP Low 15.1 0.0 3.1 14.4 15.5 48.1 0.0 48.1
ASHP Medium 12.6 0.0 3.1 14.5 15.5 45.7 0.0 45.7
ASHP High 10.3 0.0 3.1 14.5 14.4 42.3 0.0 42.3
Table 51: Hotel, naturally ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 107.9 0.0 3.9 17.7 199.8 329.3 5.5 323.8
Gas+PV Low 106.5 0.0 5.0 12.8 195.6 319.8 7.0 312.9
Gas+PV Medium 108.2 0.0 5.0 12.9 195.6 321.6 14.0 307.7
Gas+PV High 86.1 0.0 5.0 12.9 195.6 299.5 14.0 285.6
ASHP Low 28.8 0.0 5.0 12.8 73.0 119.6 0.0 119.6
ASHP Medium 25.2 0.0 5.0 12.9 73.0 116.1 0.0 116.1
ASHP High 18.4 0.0 5.0 12.9 67.7 103.9 0.0 103.9
Table 52: Hotel, AC, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 38.3 11.7 46.3 17.7 199.8 313.8 16.6 297.2
Gas+PV Low 40.9 7.9 47.4 12.7 195.6 304.4 7.0 297.5
Gas+PV Medium 40.1 4.9 42.3 12.8 195.6 295.7 14.0 281.8
Gas+PV High 23.1 5.5 41.6 12.8 195.6 278.6 14.0 264.7
ASHP Low 11.0 7.9 47.4 12.7 73.0 152.1 0.0 152.1
ASHP Medium 9.3 4.9 42.3 12.8 73.0 142.4 0.0 142.4
ASHP High 4.9 5.5 41.6 12.8 67.7 132.6 0.0 132.6
Table 53: Primary School, naturally ventilated, biomass heating base case modelled energy consumption by end-use and onsite generation. Units - Energy (kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 33.2 0.0 2.0 11.2 12.7 59.1 5.3 53.8
Gas+PV Low 25.9 0.0 2.6 6.6 12.6 47.7 7.3 40.4
Gas+PV Medium 24.3 0.0 2.6 6.7 12.6 46.2 14.6 31.6
Gas+PV High 19.1 0.0 2.6 6.7 12.6 41.0 14.6 26.4
ASHP Low 7.0 0.0 2.6 6.6 7.1 23.3 0.0 23.3
ASHP Medium 5.6 0.0 2.6 6.7 7.1 22.0 0.0 22.0
ASHP High 4.1 0.0 2.6 6.7 6.8 20.2 0.0 20.2
Table 54: Primary School, mechanically ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 9.9 0.0 5.8 10.9 9.8 36.4 5.4 31.0
Gas+PV Low 13.6 0.0 6.3 6.7 12.6 39.2 7.3 31.9
Gas+PV Medium 11.5 0.0 6.3 6.8 12.6 37.2 14.6 22.6
Gas+PV High 6.4 0.0 6.3 6.8 12.6 32.1 14.6 17.5
ASHP Low 3.7 0.0 6.3 6.7 7.1 23.8 0.0 23.8
ASHP Medium 2.7 0.0 6.3 6.8 7.1 22.9 0.0 22.9
ASHP High 1.4 0.0 6.3 6.8 6.8 21.3 0.0 21.3
Table 55: Primary School, naturally ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 22.1 0.0 2.0 12.9 9.8 46.8 4.7 42.1
Gas+PV Low 25.9 0.0 2.6 6.7 12.6 47.8 7.3 40.5
Gas+PV Medium 24.3 0.0 2.6 6.8 12.6 46.2 14.6 31.6
Gas+PV High 19.1 0.0 2.6 6.8 12.6 41.0 14.6 26.4
ASHP Low 7.0 0.0 2.6 6.7 7.1 23.4 0.0 23.4
ASHP Medium 5.6 0.0 2.6 6.8 7.1 22.1 0.0 22.1
ASHP High 4.1 0.0 2.6 6.8 6.8 20.3 0.0 20.3
Table 56: Retail Unit, AC, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 9.0 48.0 23.5 49.8 1.9 132.1 5.4 126.7
Gas+PV Low 12.6 26.1 22.4 20.3 1.6 83.1 7.3 75.9
Gas+PV Medium 9.6 23.7 21.6 21.0 1.6 77.5 14.6 62.9
Gas+PV High 6.9 23.4 21.4 21.0 1.6 74.3 14.6 59.6
ASHP Low 3.4 26.1 22.4 20.3 1.6 73.9 0.0 73.9
ASHP Medium 2.2 23.7 21.6 21.0 1.6 70.1 0.0 70.1
ASHP High 1.5 23.4 21.4 21.0 1.6 68.9 0.0 68.9
Table 57: Retail Unit, AC, electric ASHP heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 2.1 50.1 23.5 50.4 0.9 127.0 5.4 121.6
Gas+PV Low NA NA NA NA NA NA NA NA
Gas+PV Medium NA NA NA NA NA NA NA NA
Gas+PV High NA NA NA NA NA NA NA NA
ASHP Low 3.5 26.1 22.4 20.3 1.6 74.0 0.0 74.0
ASHP Medium 2.3 23.7 21.6 21.0 1.6 70.2 0.0 70.2
ASHP High 1.5 23.4 21.4 21.0 1.6 68.9 0.0 68.9
Table 58: Shallow-plan Office, naturally ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy ( kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 32.1 0.0 1.8 17.6 3.1 54.5 5.4 49.1
Gas+PV Low 33.6 0.0 1.8 10.1 2.7 48.1 7.3 40.8
Gas+PV Medium 33.0 0.0 1.8 10.3 2.7 47.7 14.6 33.1
Gas+PV High 23.1 0.0 1.8 10.3 2.7 37.8 14.6 23.2
ASHP Low 9.1 0.0 1.8 10.1 2.7 23.6 0.0 23.6
ASHP Medium 7.7 0.0 1.8 10.3 2.7 22.4 0.0 22.4
ASHP High 4.9 0.0 1.8 10.3 2.7 19.7 0.0 19.7
Table 59: Distribution Warehouse, naturally ventilated, gas heating base case modelled energy consumption by end-use and onsite generation. Units - Energy (kWh/m²)
Model Name Heating Cooling Aux. Lighting DHW Total PV gen. Total minus gen.
2015 compliant 85.3 0.0 0.3 18.2 17.4 121.1 5.4 115.7
Gas+PV Low 92.1 0.0 0.4 12.0 16.1 120.6 7.3 113.3
Gas+PV Medium 84.7 0.0 0.4 11.9 16.1 113.1 14.6 98.5
Gas+PV High 72.7 0.0 0.4 11.9 16.1 101.1 14.6 86.5
ASHP Low 35.8 0.0 5.2 12.0 8.5 61.4 0.0 61.4
ASHP Medium 28.5 0.0 5.2 11.9 8.5 54.1 0.0 54.1
ASHP High 22.8 0.0 5.2 11.9 8.1 48.0 0.0 48.0

149. The majority of the sample buildings modelled include a wet heating system in the base case. The exception to this is the distribution warehouse which uses a radiant gas-fired heating system in the main storage area although a wet system is used in the adjoining office areas. A gas-fired radiant heating system is not compatible with an ASHP so the three ASHP options shown in Table 59 are based on this heating system being converted to a wet radiant heating system; this can be seen in Table 59 as the auxiliary energy (primarily the LTHW pump) increases for the ASHP options.

150. When comparing the results shown in Table 48 to Table 59 it is important to remember that the base case compliant buildings vary in terms of lighting efficacy, PV area and, where applicable, cooling and ASHP efficiency (see Table 12). One example of where this can be seen is in comparing the results for the naturally ventilated primary school heating with biomass and the variation heated with gas (Table 53 and Table 55). In comparing these two results it can be seen that the base case heating, lighting and PV output all vary. This, combined with the effects of changing the heating fuels, has a knock-on effect on the calculated savings achieved by the six improvement options.

151. The results show that the CO2 emissions increase in the case of the biomass-heated primary school. This is due to the very low emission factor for biomass compared to the higher emission rate for gas and electricity, see Table 14 and Table 15. The primary energy factors for these fuels is similar so the primary energy results do show a saving for all six options considered.

152. To aid comparison of the many results shown in Table 36 to Table 59 two summary tables have been produced; Table 60 and Table 61 show the calculated improvement margins on the base case models for primary energy and CO2 respectively. These results are shown graphically in Figure 21 and Figure 22.

Table 60: Summary of Primary Energy improvement margins
Building
Sub-type
Deep Office; Gas; AC Deep Office; Elec; AC Hospital; Gas; NV Hotel; Gas; NV Hotel; Gas; AC Primary School; Biomass; NV Primary School; Gas; MV Primary School; Gas; NV Retail; Gas; AC Retail; Elec; AC Shallow Office; Gas; NV Warehouse Distribution; Gas; NV Minimum Maximum
Gas+PV Low 22% NA 22% 4% 0% 19% -2% 6% 41% NA 20% 3% -2% 41%
Gas+PV Medium 37% NA 30% 6% 6% 40% 31% 30% 51% NA 38% 17% 6% 51%
Gas+PV High 44% NA 34% 13% 12% 50% 45% 42% 53% NA 56% 27% 12% 56%
ASHP Low 16% 13% 54% 51% 36% 40% 8% 31% 40% 39% 41% 30% 8% 51%
ASHP Medium 22% 20% 56% 52% 40% 44% 12% 34% 43% 42% 44% 39% 12% 52%
ASHP High 25% 23% 60% 57% 44% 48% 18% 40% 44% 43% 51% 46% 18% 57%
Table 61: Summary of CO2 improvement margins
Building
Sub-type
Deep Office; Gas; AC Deep Office; Elec; AC Hospital; Gas; NV Hotel; Gas; NV Hotel; Gas; AC Primary School; Biomass; NV Primary School; Gas; MV Primary School; Gas; NV Retail; Gas; AC Retail; Elec; AC Shallow Office; Gas; NV Warehouse Distribution; Gas; NV Minimum
[excl. biomass primary school]
Maximum
Gas+PV Low 20% NA 12% 3% 0% -225% -5% 1% 38% NA 13% 1% -5% 38%
Gas+PV Medium 34% NA 17% 4% 4% -174% 19% 16% 48% NA 25% 12% 4% 48%
Gas+PV High 45% NA 22% 11% 10% -130% 38% 30% 52% NA 47% 22% 10% 52%
ASHP Low 28% 14% 72% 75% 64% -35% 41% 59% 44% 39% 64% 62% 14% 75%
ASHP Medium 34% 20% 74% 75% 66% -27% 44% 61% 47% 42% 66% 67% 20% 75%
ASHP High 36% 23% 76% 78% 68% -16% 48% 65% 48% 43% 70% 70% 23% 78%
Figure 21: Summary of primary energy improvement margins
Graph summarising the primary energy improvement margins across the 12 modelled building examples, as listed in Table 60.
Figure 22: Summary of CO2 improvement margins
Graph summarising the carbon dioxide emissions improvement margins across the 12 modelled building examples, as listed in Table 61.

153. The analysis identified the following key findings:

  • Savings in both primary energy and CO2 improve from “Low” to “Medium” and from “Medium” to “High” in all cases.
  • Primary energy savings over the base case are achieved in every case except the “Gas+PV Low” option for the mechanically ventilated primary school (this is due to an increase in DHW energy associated with the centralized system (see Section 1.9).
  • CO2 savings over the base case are achieved in all cases except the same “Gas+PV Low” option for the mechanically ventilated primary school (see above) and all the options for the biomass-heated primary school (see Paragraph 151).

154. There is no clear correlation between the Gas+PV and ASHP results. For example, it is not possible to say that one of the Gas+PV options is approximately equal to one of the ASHP options in all cases.

155. In most cases the ASHP options achieve greater percentage savings than the equivalent Gas+PV options. This means that if one of the Gas+PV options is adopted for the new standard then a building using an ASHP is generally going to be able to comply. However, this is not the case for the primary energy of the deep-plan office with gas heating. In this instance the greater primary energy savings are achieved by the Gas+PV option because these options include PV and, in this case, the PV is more effective than the ASHP.

156. The reason for this is that there is only a weak link between the factors which influence the savings achieved by an ASHP and PV. As is explained in Paragraphs 126 and 133, the ability of an ASHP on the notional building to achieve energy and carbon savings is driven by the building’s demand for space heating and DHW; these in turn are influenced by the built-form and the NCM activities (which define DHW loads, heating set points and occupancy hours etc.). The ability of the notional building’s PV array to achieving savings is influenced by the size of the array which is defined in terms of either the roof area or the GIA (see Table 33) and this is a function of the build-form alone. These relationships are illustrated in Figure 23:

Figure 23: Illustration of interdependencies influencing ASHP and PV energy and CO2 savings
Venn diagram illustrating the interrelationship between savings due to use of an air source heat pump or photovoltaics.

157. The only factor linking ASHP savings to PV savings is the built form. However, it is different elements of the built form which influence the savings of the two technologies. The space heating demand is influence by the surface to volume ratio of the building whilst the area of PV is influenced by the roof/GIA ratio. In some cases, there is a weak link between these two parameters, for example a large low-rise building such as a warehouse will have a high roof/GIA ratio and a high surface/volume ratio. However, Figure 24 shows that it is possible to alter one of these ratios without changing the other and so they are fundamentally independent variables.

158. For this reason, it is not possible to select an area of PV which will equalize the savings achieved (or the ease of compliance) by the Gas+PV and ASHP options.

Figure 24: Illustration of how surface/volume ratio and roof/ GIA ratio are independent
Graphic illustrating how surface to volume ratio and roof area to gross internal area are independent factors, driven by built form.

159. The results show that some of the “Gas+PV Low” options may result in an increase in primary energy and CO2 relative to the current 2015 standard; this is particularly likely for buildings with large floor areas with a high DHW demand such as education buildings. For this reason, this option is not recommended.

1.10.2 Fuel Mix

160. The SBEM modelling results were used to assess the benefits at a national level. The 12 sample buildings and annual build numbers used for the baseline were assumed in the counterfactual scenarios, and these were assumed to be unchanged over the analysis period.

161. Two alternative fuel mix scenarios, agreed with the Scottish Government, were considered. In both cases, these were modelled separately for the low, medium and high cases, and a full transition to the new standards is assumed to be achieved by 2025, as explained below. The fuel mix scenarios are:

  • A core ‘with fossil fuels’ case.
  • A ‘without fossil fuels’ case.

162. Table 62 sets out the fuels assumed for the twelve sample buildings selected in Task 1 under each fuel mix scenario. The table shows:

  • The baseline fuels which are adopted in the current compliant solution (see Task 1).
  • The ‘with fossil fuels’ case based on the “Low”, “Medium” and “High” notional buildings which continue to allow for higher carbon fuels. In general, the same heating system is adopted as for the baseline. The exception to this is the biomass boiler used for one of the baseline primary schools. Given the introduction of a primary energy metric, there is significantly less benefit of adopting biomass compared to gas heating. For the purpose of this analysis, it is assumed that the primary school will now adopt gas heating. In cases where the notional building uses gas it will also include PV; where the building uses ASHP then PV will not be included[18].
  • The ‘without fossil fuels’ case assumes that in the future the gas notional building is excluded and so the most viable route to compliance is likely to include low carbon heating. For the purpose of this analysis, it is assumed that all of the buildings will be heated with an ASHP.
Table 62: Twelve building sub-types selected for to reflect national build profile – fuel mix assumptions
Building Sub-types - baseline Floor Area (m²) Floor Area (%) Heating and DHW fuels
Baseline For ‘with fossil fuels’ case For ‘without fossil fuels’ case
Deep Office AC; Gas; AC 52,289 8% Gas boiler Gas boiler ASHP
Deep Office AC; Elec; AC 56,345 8% ASHP ASHP ASHP
Hospital; Gas; NV 51,382 8% Gas boiler Gas boiler ASHP
Hotel; Gas; NV 22,548 3% Gas boiler Gas boiler ASHP
Hotel; Gas; AC 29,285 4% Gas boiler Gas boiler ASHP
Primary School; Biomass; NV 39,732 6% Biomass boiler Gas boiler ASHP
Primary School; Gas; MV 80,818 12% Gas boiler Gas boiler ASHP
Primary School; Gas; NV 151,577 23% Gas boiler Gas boiler ASHP
Retail; Gas; AC 56,069 8% Gas boiler Gas boiler ASHP
Retail; Elec; AC 39,465 6% ASHP ASHP ASHP
Shallow Office NV; Gas; NV 49,111 7% Gas boiler Gas boiler ASHP
Warehouse Distribution; Gas; NV 43,494 6% Radiant gas heater Radiant gas heater ASHP
Total: 672,115 100%

1.10.3 Transitional Period

163. The national profile modelling assumes a transitional period as new standards are introduced (i.e. not all buildings built in 2021 will be to 2021 standards). The assumptions made were agreed with Scottish Government and are set out in Table 63.

Table 63: Transitional period assumptions for 2021 standards
Proportions of new non-domestic buildings built to relevant standard in each year 2021 2022 2023 2024 2025 onwards
2015 standard 80% 60% 40% 20% 0%
2021 standard 20% 40% 60% 80% 100%

Source: Agreed with Scottish Government.

1.11 National impacts (benefits) with fossil fuels

164. To form an initial estimate of the carbon benefit of the different potential future standards, prior to undertaking a full CBA, the energy results summarised in Section 1.10.1 were applied to the national build profile, taking into account the assumptions on build/fuel mix and build rates set out in Sections 1.10.2 and 1.10.3. Initially the core ‘with fossil fuels’ scenario was assessed.

165. A 25-year analysis period was used. The three counterfactual cases (“Low”, “Medium” and “High”) were compared to the 2015 compliant base case. The carbon emission factors applied for gas and electricity are those published by BEIS to support the HM Treasury Green Book supplementary appraisal guidance on valuing energy use and greenhouse gas (GHG) emissions (BEIS, 2019). The factors for electricity are projected to decrease over time and are summarised in Table 64. The factor for gas is 0.184kgCO2e/kWh. The Green Book does not include a carbon emission factor for biomass so the value proposed for Section 6 is used in this analysis (0.029kgCO2e/kWh), this only affects one of the schools (weighted to 6% of the national build floor area) so this is not expected to have a large impact on the results.

Table 64: Carbon emission factors used in benefit analysis – electricity ( kgCO2e/kWh)
Year 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
Consumption 0.278 0.264 0.250 0.236 0.220 0.203 0.186 0.167 0.148 0.127 0.113 0.101 0.090
Year (cont.) 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045
Consumption 0.080 0.071 0.064 0.057 0.051 0.045 0.040 0.039 0.038 0.036 0.035 0.034

Notes For non-domestic buildings it has been assumed that all PV output is used onsite with negligible export; therefore the PV output is assumed to offset electricity demand using the same CO2 factor.

Source BEIS, Green Book supplementary guidance: valuation of energy use and greenhouse gas emissions for appraisal – data tables 1 (electricity – long-run marginal commercial consumption-based figures and generation-based figures) and 2a (natural gas) (BEIS, 2019).

166. It should be noted that the carbon emission factors are different from those used in SBEM. They are lower for gas, and for electricity they are initially significantly higher but are projected to decrease over time becoming lower from 2030 onwards and continuing to decrease until 2050. A different calculation of carbon savings from the counterfactual cases across the build mix using the proposed carbon emission factors (for a single year) is given in Section 1.14.

167. The results by year are presented in Table 65. Total emissions increase over time as the total cumulative floor area included in the analysis increases, though emission factors for electricity decrease. The estimated total carbon savings for the counterfactual cases across the analysis period are summarised in Table 66. This shows that the “Low”, “Medium” and “High” cases are estimated to achieve a 7%, 14% and 21% reduction in carbon emissions compared to the base case respectively.

Table 65: Annual carbon emissions for base case and counterfactual cases – ‘with fossil fuels’ scenario ( ktCO2e/yr)
Year 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
Base 13 25 38 49 61 72 83 93 103 112 121 130 138
Low 12 24 36 46 56 66 76 85 94 102 111 119 127
Medium 12 23 34 43 52 61 69 77 85 93 101 108 116
High 12 23 33 42 50 58 65 73 80 87 94 101 107
Year (cont.) 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 ALL
Base 146 154 162 169 177 184 191 199 206 213 220 227 3,286
Low 135 143 150 158 165 172 179 187 194 201 208 215 3,061
Medium 123 130 137 144 151 158 165 172 178 185 192 199 2,811
High 114 120 127 133 139 145 151 157 163 169 175 181 2,599
Table 66: Total carbon emissions for counterfactual cases – ‘with fossil fuels’ scenario
Total carbon saving (ktCO2e/yr) % reduction compared to base case
Low 225 7%
Medium 475 14%
High 688 21%

1.12 National impacts (benefits) without fossil fuels

168. The ‘without fossil fuels’ scenario was also assessed, using the same process and assumptions as for the ‘with fossil fuels’ scenario, set out in sections 1.10 and 1.11. The results by year are presented in Table 67. The estimated total carbon savings for the counterfactual cases across the analysis period are summarised in Table 68.

169. This shows that under the ‘without fossil fuels’ scenario, the “Low”, “Medium” and “High” cases are estimated to achieve a 39%, 42% and 44% reduction in carbon emissions compared to the base case respectively. As would be expected, this is significantly higher than the estimated reductions under the ‘with fossil fuels’ scenarios, where most new buildings are assumed to be gas-heated over the analysis period.

Table 67: Annual carbon emissions for base case and counterfactual cases – ‘without fossil fuels’ scenario (ktCO 2e/yr)
Year 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
Base 13 25 38 49 61 72 83 93 103 112 121 130 138
Low 12 23 33 41 48 55 61 66 71 75 79 82 85
Medium 12 23 32 40 47 53 59 64 68 72 75 78 81
High 12 22 32 39 46 51 57 61 66 69 72 75 78
Year (cont.) 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 ALL
Base 146 154 162 169 177 184 191 199 206 213 220 227 3,286
Low 87 90 92 93 95 97 98 99 100 101 103 104 1,888
Medium 84 86 88 89 91 92 94 95 96 97 98 99 1,813
High 80 82 84 85 87 88 89 90 92 93 94 94 1,738
Table 68: Total carbon emissions for counterfactual cases – ‘without fossil fuels’ scenario
Total carbon saving (ktCO2e) % reduction compared to base case
Low 1,398 43%
Medium 1,474 44%
High 1,548 47%

1.13 National impacts (costs)

170. The capital costs (in 2020 prices) of each building type for the 2015, low, medium and high cases, and for both gas heating and ASHP, are shown in Table 69 to Table 80. Two of the twelve sample buildings use an electric ASHP as the base case heating scenario. For these two building the results for the three gas-heated options, listed above, have been omitted as not necessary for the analysis.

Table 69: Capital costs by case and fuel type – Deep-plan Office, AC, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £3,041,890 £701,147 £738,100 £101,517 £34,742,346 £39,325,000 0%
Gas+PV low £2,982,600 £705,587 £1,004,300 £146,636 £34,742,346 £39,581,469 1%
Gas+PV medium £3,085,060 £735,553 £1,004,300 £233,051 £34,742,346 £39,800,310 1%
Gas+PV high £3,248,350 £761,524 £1,004,300 £233,051 £34,742,346 £39,989,571 2%
ASHP low £2,982,600 £1,046,560 £1,004,300 £0 £34,742,346 £39,775,806 1%
ASHP medium £3,085,060 £867,622 £1,004,300 £0 £34,742,346 £39,699,328 1%
ASHP high £3,248,350 £1,145,217 £1,004,300 £0 £34,742,346 £40,140,214 2%
Table 70: Capital costs by case and fuel type – Deep-plan Office, AC, electric heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £3,041,890 £1,046,560 £738,100 £0 £34,686,000 £39,512,550 0%
Gas+PV low NA NA NA NA NA NA NA
Gas+PV medium NA NA NA NA NA NA NA
Gas+PV high NA NA NA NA NA NA NA
ASHP low £2,982,600 £1,046,560 £1,004,300 £0 £34,686,000 £39,719,460 1%
ASHP medium £3,085,060 £1,097,365 £1,004,300 £0 £34,686,000 £39,872,726 1%
ASHP high £3,248,350 £1,145,217 £1,004,300 £0 £34,686,000 £40,083,868 1%
Table 71: Capital costs by case and fuel type – Hospital, NV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £3,820,649 £573,175 £814,730 £0 £50,817,674 £56,026,227 0%
Gas+PV low £3,866,373 £580,395 £1,149,569 £162,237 £50,817,674 £56,576,247 1%
Gas+PV medium £3,970,791 £580,395 £1,149,569 £315,124 £50,817,674 £56,833,553 1%
Gas+PV high £4,133,877 £580,395 £1,149,569 £315,124 £50,817,674 £56,996,639 2%
ASHP low £3,866,373 £1,155,300 £1,149,569 £0 £50,817,674 £56,988,916 2%
ASHP medium £3,970,791 £1,189,187 £1,149,569 £0 £50,817,674 £57,127,222 2%
ASHP high £4,133,877 £1,224,769 £1,149,569 £0 £50,817,674 £57,325,889 2%
Table 72: Capital costs by case and fuel type – Hotel, NV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £613,885 £47,440 £80,057 £9,118 £2,079,397 £2,829,897 0%
Gas+PV low £620,209 £48,140 £101,390 £13,170 £2,079,397 £2,862,305 1%
Gas+PV medium £638,190 £48,140 £101,390 £26,340 £2,079,397 £2,893,456 2%
Gas+PV high £668,626 £48,140 £101,390 £26,340 £2,079,397 £2,923,892 3%
ASHP low £620,209 £104,620 £101,390 £0 £2,079,397 £2,905,616 3%
ASHP medium £638,190 £107,906 £101,390 £0 £2,079,397 £2,926,882 3%
ASHP high £668,626 £111,355 £101,390 £0 £2,079,397 £2,960,767 4%
Table 73: Capital costs by case and fuel type – Hotel, AC, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £625,534 £58,881 £80,057 £31,322 £2,236,238 £3,032,033 0%
Gas+PV low £620,209 £60,852 £101,390 £13,170 £2,236,238 £3,031,859 0%
Gas+PV medium £638,190 £62,759 £101,390 £26,340 £2,236,238 £3,064,916 1%
Gas+PV high £668,626 £64,411 £101,390 £26,340 £2,236,238 £3,097,005 2%
ASHP low £620,209 £117,332 £101,390 £0 £2,236,238 £3,075,169 1%
ASHP medium £638,190 £122,525 £101,390 £0 £2,236,238 £3,098,342 2%
ASHP high £668,626 £127,627 £101,390 £0 £2,236,238 £3,133,880 3%
Table 74: Capital costs by case and fuel type – Primary School, NV, biomass heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £1,618,866 £250,283 £143,533 £19,741 £3,219,472 £5,251,896 0%
Gas+PV low £1,634,129 £103,236 £195,299 £28,515 £3,219,472 £5,180,651 -1%
Gas+PV medium £1,671,717 £103,236 £195,299 £57,030 £3,219,472 £5,246,754 0%
Gas+PV high £1,734,691 £103,236 £195,299 £57,030 £3,219,472 £5,309,728 1%
ASHP low £1,634,129 £215,867 £195,299 £0 £3,219,472 £5,264,768 0%
ASHP medium £1,671,717 £222,462 £195,299 £0 £3,219,472 £5,308,950 1%
ASHP high £1,734,691 £229,386 £195,299 £0 £3,219,472 £5,378,848 2%
Table 75: Capital costs by case and fuel type – Primary School, MV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £1,645,659 £101,831 £143,533 £19,741 £3,997,619 £5,908,383 0%
Gas+PV low £1,634,129 £103,236 £195,299 £28,515 £3,997,619 £5,958,798 1%
Gas+PV medium £1,671,717 £103,236 £195,299 £57,030 £3,997,619 £6,024,901 2%
Gas+PV high £1,734,691 £103,236 £195,299 £57,030 £3,997,619 £6,087,875 3%
ASHP low £1,634,129 £215,867 £195,299 £0 £3,997,619 £6,042,915 2%
ASHP medium £1,671,717 £222,462 £195,299 £0 £3,997,619 £6,087,097 3%
ASHP high £1,734,691 £229,386 £195,299 £0 £3,997,619 £6,156,995 4%
Table 76: Capital costs by case and fuel type – Primary School, NV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £1,618,866 £101,831 £138,827 £18,271 £3,592,930 £5,470,725 0%
Gas+PV low £1,634,129 £103,236 £195,299 £28,515 £3,592,930 £5,554,109 2%
Gas+PV medium £1,671,717 £103,236 £195,299 £57,030 £3,592,930 £5,620,212 3%
Gas+PV high £1,734,691 £103,236 £195,299 £57,030 £3,592,930 £5,683,186 4%
ASHP low £1,634,129 £215,867 £195,299 £0 £3,592,930 £5,638,225 3%
ASHP medium £1,671,717 £222,462 £195,299 £0 £3,592,930 £5,682,408 4%
ASHP high £1,734,691 £229,386 £195,299 £0 £3,592,930 £5,752,306 5%
Table 77: Capital costs by case and fuel type – Retail, AC, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £1,079,070 £80,365 £121,250 £10,487 £3,083,828 £4,375,000 0%
Gas+PV low £1,072,945 £80,770 £173,250 £15,148 £3,083,828 £4,425,941 1%
Gas+PV medium £1,091,398 £85,120 £173,250 £30,297 £3,083,828 £4,463,892 2%
Gas+PV high £1,115,739 £88,890 £173,250 £30,297 £3,083,828 £4,492,003 3%
ASHP low £1,072,945 £110,767 £173,250 £0 £3,083,828 £4,440,790 1%
ASHP medium £1,091,398 £117,018 £173,250 £0 £3,083,828 £4,465,494 2%
ASHP high £1,115,739 £122,784 £173,250 £0 £3,083,828 £4,495,601 3%
Table 78: Capital costs by case and fuel type – Retail, AC, electric heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £1,079,070 £110,767 £121,250 £0 £3,063,913 £4,375,000 0%
Gas+PV low NA NA NA NA NA NA NA
Gas+PV medium NA NA NA NA NA NA NA
Gas+PV high NA NA NA NA NA NA NA
ASHP low £1,072,945 £110,767 £173,250 £0 £3,063,913 £4,420,875 1%
ASHP medium £1,091,398 £117,018 £173,250 £0 £3,063,913 £4,445,579 2%
ASHP high £1,115,739 £122,784 £173,250 £0 £3,063,913 £4,475,686 2%
Table 79: Capital costs by case and fuel type – Shallow Plan Office, NV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 £764,536 £90,200 £131,760 £18,122 £4,017,382 £5,022,000 0%
Gas+PV low £769,990 £91,080 £179,280 £26,176 £4,017,382 £5,083,908 1%
Gas+PV medium £797,465 £91,080 £179,280 £52,353 £4,017,382 £5,137,559 2%
Gas+PV high £841,433 £91,080 £179,280 £52,353 £4,017,382 £5,181,527 3%
ASHP low £769,990 £159,456 £179,280 £0 £4,017,382 £5,126,108 2%
ASHP medium £797,465 £163,586 £179,280 £0 £4,017,382 £5,157,713 3%
ASHP high £841,433 £167,923 £179,280 £0 £4,017,382 £5,206,017 4%
Table 80: Capital costs by case and fuel type – Warehouse Distribution, NV, gas heating base case
Cost category Percentage uplift on 2015
Fabric Heating and cooling Lighting and ventilation Photovoltaics Balance of construction cost Total
BS2015 case £2,222,175 £114,188 £272,914 £41,631 £5,655,598 £8,306,505 0%
Gas+PV low £2,301,416 £114,746 £322,535 £60,134 £5,655,598 £8,454,427 2%
Gas+PV medium £2,434,775 £115,583 £322,535 £120,267 £5,655,598 £8,648,757 4%
Gas+PV high £2,549,856 £116,308 £322,535 £120,267 £5,655,598 £8,764,563 5%
ASHP low £2,301,416 £340,268 £322,535 £0 £5,655,598 £8,619,816 4%
ASHP medium £2,434,775 £349,037 £322,535 £0 £5,655,598 £8,761,944 5%
ASHP high £2,549,856 £358,091 £322,535 £0 £5,655,598 £8,886,079 7%

171. These capital cost estimates are based on a ‘central belt’ price level. In other areas of Scotland prices may be different reflecting the availability and costs of materials and labour. Drawing on Currie & Brown’s experience in delivering projects across Scotland[19] the following indexed adjustments on the base central belt costs (index of 100) are considered reasonable to reflect the additional costs of working in more remote parts of the country. The impact on the build cost of the primary school with gas for the different cases is shown in Table 81 for the highest cost location the Western Isles.

  • Central Belt (Glasgow, Edinburgh etc) – 100
  • Borders / Dumfries & Galloway - 103
  • Grampian (Aberdeen) - 103
  • Highland - 110
  • Orkney & Shetland - 125
  • Western Isles – 130
Table 81: Potential variation in build costs for non-domestic buildings built in the Western Isles – Primary School, NV, gas heating base case
Central cost Cost for projects in Western Isles Variation in overall cost from 2015 base
BS2015 case £5,470,725 £7,111,943 £0
Gas+PV low £5,542,579 £7,205,353 £93,410
Gas+PV medium £5,608,682 £7,291,287 £179,344
Gas+PV high £5,671,656 £7,373,153 £261,210
ASHP low £5,626,696 £7,314,704 £202,762
ASHP medium £5,670,878 £7,372,142 £260,199
ASHP high £5,740,776 £7,463,009 £351,066

172. The capital, maintenance and renewal, energy (variable cost) and lifetime costs of each case and fuel type are shown in Table 82. These costs are the net present value costs over a 60-year period for a building constructed in 2021 (in 2021 prices). Information is presented for each building type against the relevant 2015 base case specification and fuel type. Lifetime energy costs are derived from energy price projections published by BEIS, renewal and maintenance costs are derived on an elemental basis in line with the assumptions in Appendix A: Cost Breakdown. Renewal and maintenance costs reflect only those elements that are linked to the variations in specification and exclude other common elements such as decoration and other services (e.g. fan coils, lifts, etc.).

Table 82: Lifetime costs by building, case and heating type (£ present value per building)
Building type and case Change in capital cost Change in energy cost Change in renewals cost Change in maintenance cost Change in lifetime cost
Deep Office AC; Gas
Gas low case £256,469 -£296,677 £325,814 £0 £285,605
Gas medium case £475,310 -£500,088 £391,932 £0 £367,154
Gas high case £664,571 -£526,398 £446,084 £0 £584,258
ASHP low case £450,806 -£285,833 £610,590 £0 £775,563
ASHP medium case £604,072 -£500,100 £667,187 £0 £771,158
ASHP high case £815,214 -£528,801 £743,581 £0 £1,029,994
Deep Office AC; Elec
Gas low case NA NA NA NA NA
Gas medium case NA NA NA NA NA
Gas high case NA NA NA NA NA
ASHP low case £206,910 -£427,625 £304,700 £0 £83,985
ASHP medium case £360,176 -£652,344 £361,296 £0 £69,127
ASHP high case £571,318 -£682,446 £437,690 £0 £326,563
Hospital; Gas; NV
Gas low case £550,020 -£894,876 £451,688 £0 £106,833
Gas medium case £807,326 -£1,153,387 £519,851 £0 £173,790
Gas high case £970,411 -£1,201,031 £552,553 £0 £321,934
ASHP low case £962,689 -£621,413 £965,248 £0 £1,306,524
ASHP medium case £1,100,995 -£954,872 £1,013,533 £0 £1,159,655
ASHP high case £1,299,662 -£1,074,093 £1,082,403 £0 £1,307,971
Hotel; Gas; NV
Gas low case £32,408 -£17,849 £26,928 £0 £41,488
Gas medium case £63,559 -£36,678 £35,189 £0 £62,070
Gas high case £93,995 -£51,557 £42,890 £0 £85,328
ASHP low case £75,719 £71,939 £78,477 £0 £226,135
ASHP medium case £96,985 £41,468 £85,398 £0 £223,851
ASHP high case £130,870 £6,442 £96,606 £0 £233,919
Hotel; Gas; AC
Gas low case -£173 £5,429 £19,532 £0 £24,788
Gas medium case £32,884 -£38,303 £28,938 £0 £23,519
Gas high case £64,972 -£50,053 £37,632 £0 £52,551
ASHP low case £43,137 £88,146 £71,082 £0 £202,365
ASHP medium case £66,310 £39,948 £79,148 £0 £185,406
ASHP high case £101,848 £11,448 £91,348 £0 £204,643
Primary School; Biomass; NV
Gas low case -£71,245 -£59,594 -£105,004 -£773 -£236,617
Gas medium case -£5,142 -£107,221 -£88,231 -£773 -£201,368
Gas high case £57,832 -£114,785 -£73,069 -£773 -£130,796
ASHP low case £12,872 -£41,857 -£3,115 -£773 -£32,873
ASHP medium case £57,054 -£95,604 £10,229 -£773 -£29,095
ASHP high case £126,952 -£107,705 £32,430 -£773 £50,903
Building type and case Change in capital cost Change in energy cost Change in renewals cost Change in maintenance cost Change in lifetime cost
Primary School; Gas; MV
Gas low case £50,415 £5,244 £63,979 £0 £119,638
Gas medium case £116,518 -£43,150 £80,751 £0 £154,120
Gas high case £179,492 -£50,579 £95,914 £0 £224,826
ASHP low case £134,532 £20,110 £165,868 £0 £320,510
ASHP medium case £178,714 -£31,489 £179,211 £0 £326,437
ASHP high case £248,612 -£41,965 £201,412 £0 £408,059
Primary School; Gas; NV
Gas low case £83,384 -£11,766 £70,828 £0 £142,446
Gas medium case £149,487 -£59,391 £87,601 £0 £177,696
Gas high case £212,461 -£66,954 £102,763 £0 £248,270
ASHP low case £167,500 £5,968 £172,717 £0 £346,185
ASHP medium case £211,683 -£47,774 £186,061 £0 £349,970
ASHP high case £281,581 -£59,871 £208,262 £0 £429,971
Retail; Gas; AC
Gas low case £50,941 -£173,500 £61,640 £0 -£60,919
Gas medium case £88,892 -£208,990 £70,787 £0 -£49,310
Gas high case £117,003 -£212,727 £77,214 £0 -£18,510
ASHP low case £65,790 -£171,935 £85,722 £0 -£20,423
ASHP medium case £90,494 -£209,007 £91,419 £0 -£27,095
ASHP high case £120,601 -£213,168 £99,874 £0 £7,307
Retail; Elec; AC
Gas low case NA NA NA NA NA
Gas medium case NA NA NA NA NA
Gas high case NA NA NA NA NA
ASHP low case £45,875 -£182,238 £59,521 £0 -£76,842
ASHP medium case £70,579 -£219,439 £65,217 £0 -£83,643
ASHP high case £100,686 -£223,684 £73,672 £0 -£49,326
Shallow Office NV; Gas
Gas low case £61,908 -£40,920 £58,797 £0 £79,785
Gas medium case £115,559 -£82,459 £73,688 £0 £106,788
Gas high case £159,527 -£95,616 £85,939 £0 £149,850
ASHP low case £104,108 -£33,728 £117,175 £0 £187,554
ASHP medium case £135,713 -£82,562 £126,964 £0 £180,115
ASHP high case £184,017 -£98,172 £143,623 £0 £229,469
Distribution; Gas; NV
Gas low case £147,922 -£47,887 £106,318 £0 £206,352
Gas medium case £342,251 -£168,598 £192,647 £0 £366,300
Gas high case £458,058 -£205,438 £245,276 £0 £497,896
ASHP low case £313,311 £226,266 £312,796 £4,651 £857,023
ASHP medium case £455,438 £32,681 £385,822 £4,651 £878,591
ASHP high case £579,574 -£47,764 £446,916 £4,651 £983,376

1.14 Comparison with Sullivan Report recommendations

173. The overall reduction in carbon emissions across the build mix for the six counterfactual cases has been compared to the Sullivan Report recommendations. For non-domestic buildings, the Sullivan Report recommends at least 75% on 2007 standards. This equates to an aggregate emissions reduction of at least 37% on 2015 standards across a notional annual build mix.

174. For this comparison, carbon emission savings were estimated using a single analysis year and proposed SBEM carbon emission factors. The same build rates and fuel mix were used as for the analyses with and without fossil fuels above (see Table 62), and it is assumed that 100% of buildings are built to 2021 standards in the year assessed.

175. The six counterfactual cases were again compared to the 2015 compliant base case:

  • Gas+PV Low
  • Gas+PV Medium
  • Gas+PV High
  • ASHP Low
  • ASHP Medium
  • ASHP High

176. The estimated total carbon emissions and savings for the year are summarised in Table 83. The percentage reductions are higher than in the benefit analysis for the core scenario presented in Sections 1.11 and 1.12 above mainly due to differences in the carbon emission factors used for the different analyses. The figures show that the three ASHP options considered exceed the recommendations of the Sullivan Report (i.e. a commitment to achieve a 37% improvement on 2015 standards) whilst none of the Gas+PV options achieve this standard.

Table 83: Total carbon emissions and savings for base, low, medium and high cases – Sullivan Report comparison (based on a single year and proposed SBEM carbon emission factors)
Scenario Total carbon emissions for the year
(ktCO2e/yr)
Total carbon saving for the year (ktCO2e/yr) % reduction compared to base case
2015 compliant 10.20 0.00 0%
Gas+PV Low 9.39 0.81 8%
Gas+PV Medium 8.53 1.67 16%
Gas+PV High 7.66 2.54 25%
ASHP Low 4.40 5.80 57%
ASHP Medium 4.12 6.08 60%
ASHP High 3.85 6.35 62%
Sullivan Report Commitment 6.43 3.77 37%

1.15 Sensitivity analysis

177. Analysis of the EPC database extract provided by Scottish Government showed that gas-heating, ASHP-heating and biomass-heating account for over 93% of non-domestic floor area in Scotland. However, sensitivity analysis was undertaken to investigate the ability of buildings to comply with potential 2021 standards where other fuel/heating types are specified. The heating types chosen for assessment were in part based upon analysis of the EPC database and upon investigating cases where in discussion with the client it was thought that particular questions might arise which require further consideration from a policy perspective.

Table 84: Mapping of dominant heating fuel types
Heating Fuel Floor Area (%) Notes
Natural Gas 62.4% Included in core analysis
Grid Supplied Electricity 23.0%
Biomass 8.0%
District Heating 3.3% Included in sensitivity analysis
LPG 1.8%
Oil 1.2%
Waste Heat 0.3% Deemed negligible
Other 0.1%
Biogas 0.0%
Dual Fuel Appliances (Mineral + Wood) 0.0%

178. Table 84 shows that the most common other heating types used are district heating, LPG and oil. Analysis of the EPC database shows that naturally ventilated education buildings are the dominant sub-type for buildings heated with each of these three sources. Based on this analysis, the sensitivity analysis considers the impact of using each of these three fuels on the sample naturally ventilated primary school building used in the core analysis.

179. As shown in Table 85, the CO2 and primary energy factors for both LPG and oil are higher than that of gas. However, there is a greater percentage increase for primary energy which would be expected to result in a primary energy target being more challenging than an equivalent carbon target.

Table 85: Proposed primary energy and CO2 factors for selected fuels
Fuel type kgCO2/kWh kWh/kWh
Gas 0.210 1.126
LPG 0.241 1.141
Oil 0.319 1.180

180. For gas CHP district heating, a carbon target would also be more challenging than the primary energy target due to reductions in carbon emission factors for electricity. Whilst the primary energy factors for electricity have reduced, there is a significantly greater percentage reduction for carbon emission factors. With electricity emission factors reducing over time, the carbon savings associated with gas CHP electricity generation are significantly reduced making gas CHP less attractive than previously and making it harder for gas CHP heat networks to comply. In terms of both primary energy and carbon emissions, district heating also requires additional measures to comply compared to an individually-heated gas case because of the distribution losses associated with the heat network.

181. The following sensitivity cases were modelled. In each case the same individual built forms were used as in the core modelling, and compliance is assessed the potential 2021 standards in terms of primary energy. Carbon emissions were also compared to aid in the assessment of a potential secondary carbon metric.

  • DHN+PV Low
  • DHN+PV Medium
  • DHN+PV High
  • LPG+PV Low
  • LPG+PV Medium
  • LPG+PV High
  • Oil+PV Low
  • Oil+PV Medium
  • Oil+PV High

182. For each of the new fuels the following inputs have been used:

  • DHN: CO2 emissions factor = 0.41kgCO2/kWh primary energy emission factor = 1.57 kWh/kWh [20].
  • LPG: Same boiler efficiency as is used for the core gas L/M/H options.
  • Oil: Same boiler efficiency as is used for the core gas L/M/H options.

183. The results of the sensitivity tests are compared with those of the core modelling in Table 86. In addition, Figure 25 shows the primary energy results whilst Figure 26 shows those for CO2.

Table 86: Comparison of core modelling and sensitivity test results
Model Name Primary Energy CO2 Model category
BPE Margin on 2015 BER Margin on 2015
2015 compliant 57.5 0% 9.28 0% Core modelling
Gas+PV Low 56.5 2% 9.44 -2%
Gas+PV Medium 44.0 23% 8.16 12%
Gas+PV High 38.2 34% 7.07 24%
ASHP Low 41.5 28% 3.90 58%
ASHP Medium 39.5 31% 3.70 60%
ASHP High 36.5 37% 3.41 63%
CHP-DHN+PV Low 70.2 -22% 16.17 -74% Sensitivity test
CHP-DHN+PV Medium 57.2 1% 14.63 -58%
CHP-DHN+PV High 49.5 14% 12.65 -36%
LPG+PV Low 57.1 1% 10.65 -15%
LPG+PV Medium 44.6 22% 9.33 -1%
LPG+PV High 38.7 33% 8.08 13%
Oil+PV Low 58.6 -2% 13.72 -48%
Oil+PV Medium 46.0 20% 12.28 -32%
Oil+PV High 39.9 31% 10.62 -14%

184. The sensitivity analysis shows that in all cases, the alternative heat sources (CHP-fired district heating, LPG and oil boilers) would not comply with a similarly specified gas or ASHP notional building. For example, in no cases could a “Low” specification for one of the other heating fuels comply with a notional building based on either a “Low” gas or ASHP specification.

185. From this analysis it can be deduced that if the selected 2021 standard was to be:

  • “Gas+PV Low” or “Gas+PV Medium” then, with a higher degree of energy efficiency and PV generation:
  • LPG could still achieve compliance for both primary energy and CO2.
  • Oil could still achieve compliance for primary energy only.
  • ASHP Low” then, with a higher degree of energy efficiency and PV generation:
  • LPG could still achieve compliance for primary energy only.
  • Oil could still achieve compliance for primary energy only.

It also particularly highlights the challenges facing the future adoption of gas CHP.

186. It should be noted that most of the sensitivity options exceed the CO2 emissions of the 2015 compliant solution. This implies that even if the only changes to the regulations were to be to change the emissions factors and the heating fuel of the notional building then the use of CHP, LPG and Oil would be constrained.

Figure 25: Comparison of primary energy results for core modelling and sensitivity tests
Graph illustrating outcomes for CHP, LPG and Oil solutions (modelled as part of sensitivity analysis) against the 2015 baseline and gas and ASHP solutions for primary energy totals. This shows generally the same relationship for low, medium and high improvement options as for the gas modelled building, but with slightly higher primary energy totals.
Figure 26: Comparison of CO2 results for core modelling and sensitivity tests
Graph illustrating outcomes for CHP, LPG and Oil solutions (modelled as part of sensitivity analysis) against the 2015 baseline and gas and ASHP solutions. This shows generally the same relationship for low, medium and high improvement options as for the gas modelled building, but with higher emissions.

187. The building could be further improved beyond the levels of energy efficiency and PV generation considered in the core modelling. The area of PV considered is limited to the lesser of either 6.5% or 13% of GIA (depending on the Low, Medium or High option is adopted) and 50% of the roof area. In the case of the primary school the lesser value is the percentage of the GIA in both cases. Therefore it is reasonable to postulate that in a specific example this could be increased to 50% of the roof area; the effect of increasing PV in this way is shown in Table 87, Figure 27 and Figure 28.

Table 87: Comparison of core modelling and sensitivity test results assuming PV area is 50% of roof when DHN, LPG or Oil is used
Model Name Primary Energy CO2 Model category
BPE Margin on 2015 BER Margin on 2015
2015 compliant 57.5 0% 9.28 0% Core modelling
Gas+PV Low 56.5 2% 9.44 -2%
Gas+PV Medium 44.0 23% 8.16 12%
Gas+PV High 38.2 34% 7.07 24%
ASHP Low 41.5 28% 3.90 58%
ASHP Medium 39.5 31% 3.70 60%
ASHP High 36.5 37% 3.41 63%
CHP-DHN+50%PV Low 35.5 38% 13.12 -41% Sensitivity test
CHP-DHN+50%PV Medium 33.3 42% 12.52 -35%
CHP-DHN+50%PV High 25.6 55% 10.55 -14%
LPG+50%PV Low 22.3 61% 7.60 18%
LPG+50%PV Medium 20.6 64% 7.23 22%
LPG+50%PV High 14.7 74% 5.98 36%
Oil+50%PV Low 23.9 58% 10.67 -15%
Oil+50%PV Medium 22.1 62% 10.17 -10%
Oil+50%PV High 16.0 72% 8.52 8%
Figure 27: Comparison of primary energy results for core modelling and sensitivity tests showing effect of PV area = 50% of roof
Graph illustrating outcomes for CHP, LPG and Oil solutions (modelled as part of sensitivity analysis) against the 2015 baseline and gas and ASHP solutions for emission totals. This shows generally the same relationship for low, medium and high improvement options as for the gas modelled building, but with slightly higher primary energy totals and the benefit of increasing PV to 50% of roof area.
Figure 28: Comparison of CO2 results for core modelling and sensitivity tests showing effect of PV area = 50% of roof
Graph illustrating outcomes for CHP, LPG and Oil solutions (modelled as part of sensitivity analysis) against the 2015 baseline and gas and ASHP solutions for emissions totals. This shows generally the same relationship for low, medium and high improvement options as for the gas modelled building, but with slightly higher emissions totals and the benefit of increasing PV to 50% of roof area.

188. This further analysis shows that with increased PV area (where the building form allows) the range of routes to compliance using these alternative heat sources is increased:

  • LPG can achieve compliance for both primary energy and CO2 if the standard is based on any of the three Gas+PV options.
  • Oil can achieve compliance for both primary energy and CO2 if the standard is based on the Gas+PV Low option.
  • Gas CHP can achieve compliance with or primary energy only if the standard is based on any of the three Gas+PV.
  • All three heat sources can achieve compliance for primary energy only if the standard is based on any of the three Gas+PV or ASHP options.

189. It is important to note that this analysis has been undertaken on one building type. The primary school was chosen as it is the dominant building sub-type heated with each of these three sources and hence a reasonable case for sensitivity analysis. It is expected generally that all building types will find it harder to comply for LPG, oil and gas CHP district heating compared to a gas or ASHP notional building, but level of challenge will differ to some degree.

1.16 Review of the need for a carbon metric

190. The Scottish Government has indicated the intention to retain the carbon dioxide equivalent emissions target as an additional secondary metric. The Scottish Government is looking to drive down greenhouse gas emissions and will need to continue to record progress against national carbon targets.

191. Primary energy and carbon dioxide emissions targets can have different impacts depending on the fuel type. For example, as a result of grid decarbonisation, carbon emission factors for electricity are now significantly lower than gas whilst primary energy factors for electricity remain higher than gas. If the notional building was based on an ASHP, including a carbon target would result in a greater challenge for gas-heated buildings than a primary energy target alone.

192. The proposed preferred approach is to set a notional building differentiated by fuel type (gas / ASHP). As a result, the addition of a carbon metric would not be expected to have the impact of making it more difficult for gas-heated buildings to comply.

193. A potential benefit of setting a carbon target would be to introduce more differentiation between gas and higher carbon fossil fuels such as oil and LPG. As shown in the sensitivity analysis described in section 1.15, a carbon target is much more onerous than a primary energy target. Given the policy intention of phasing out fossil fuels in 2024, it could make sense to introduce a greater disincentive for higher carbon fossil fuels in 2021 which reflects their carbon impact.

194. As shown in section 1.15, it would be very challenging for buildings with gas CHP district heating to comply with a carbon target. This needs to be considered against policy aims to, for example, continue to connect to existing gas CHP-based heat networks which may change to low carbon heating sources in the future. If necessary, the target could be relaxed for district heating (e.g. introduce technology factors as per proposals for Part L 2020 in England or through a separate specific notional building targets for heat networks) or implement a solution outside of Building Standards. Differentiation between new and existing heat networks may also be useful - new heat networks could potentially be treated differently as they may be encouraged to adopt lower carbon fuels, whereas gas CHP-based networks could be more likely to be existing networks being expanded for new buildings to connect. In practice it may be challenging to define a water-tight distinction between a new district heat network and a large increase in size/capacity of an existing network. The approach for domestic buildings should be considered at the same time, as similar findings would be expected there, and it may be appropriate to have a common approach.

195. Whilst the implications of a secondary carbon metric have not been considered in detail for all possible fuel types or heating systems, the ones considered particularly relevant for new non-domestic buildings in Scotland have been discussed above. Further sensitivity analysis covering a wider range of fuel/building types or specifications could also be undertaken, and other views could be sought.


Contact

Email: buildingstandards@gov.scot