Building regulations 2025 - new non-domestic buildings: energy standard improvements - modelling report

4. Objective III

4.1 SBEM results

The 11 building sub-types were modelled using SBEM v6.1 for all specifications.

Table 49 to Table describe the delivered energy results broken down by energy end use, alongside the Building Delivered Energy Rate (BDER) and pass margin compared to the current Section 6 (2022) requirements.

Table 60 to Table 70 outline the Building Delivered Energy Rate and pass margin compared to the current Section 6 (2022) requirements, alongside the building emissions rates calculated using the current Section 6 factors and proposed MHCLG factors (refer to Appendix B for details of the current and proposed CO₂ emissions factors). Note that, where buildings use zero direct emissions heating systems, Section 6 compliance does not require that the BER is less than the TER.

Table 49: Breakdown of Actual Building Delivered Energy (kWh) for Shallow Office; DHN; NV.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	56,000	0	2,180	17,851	5,765	42,468	18.21	0.0%
Low	56,000	0	2,180	17,851	5,765	32,425	22.86	-25.5%
Med.	53,943	0	2,180	15,889	5,765	64,409	6.19	66.0%
High	45,668	0	2,180	14,836	5,765	64,273	1.93	89.4%

Table 50: Breakdown of Actual Building Delivered Energy (kWh) for Deep Office AC; Elec; AC – HP.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	20,743	72,857	179,154	126,714	31,739	89,245	28.50	0.0%
Low	20,743	72,857	179,154	126,714	31,739	108,082	26.93	5.5%
Med.	15,564	72,114	178,289	112,045	31,739	216,164	16.13	43.4%
High	8,055	63,218	171,222	101,549	31,739	216,164	13.30	53.3%

Table 51: Breakdown of Actual Building Delivered Energy (kWh) for Heath centre; DHN; MV.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	49,387	16	14,596	22,416	6,779	67,529	12.86	0.0%
Low	49,451	16	14,596	22,168	6,779	44,922	24.10	-87.4%
Med.	46,720	16	14,596	19,676	6,779	77,362	5.23	59.4%
High	37,489	11	14,596	17,997	6,779	76,540	0.17	98.7%

Table 52: Breakdown of Actual Building Delivered Energy (kWh) for Hotel; Elec; NV – DE.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	86,830	0	2,351	9,266	183,464	0	265.27	2.2%
Low	86,941	0	2,351	8,984	183,464	16,316	249.75	7.9%
Med.	84,906	0	2,351	8,110	183,464	32,632	231.66	14.6%
High	76,699	0	2,351	7,596	183,464	32,632	223.46	17.6%

Table 53: Breakdown of Actual Building Delivered Energy (kWh) for Retail; Elec; AC – HP.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	3,685	41,873	23,031	19,441	2,051	10,636	63.56	0.0%
Low	3,689	41,658	23,031	18,456	2,051	28,146	48.59	23.5%
Med.	2,689	42,485	22,883	16,647	2,051	112,585	-20.66	132.5%
High	1,809	39,642	22,091	15,367	2,051	112,585	-25.30	139.8%

Table 54: Breakdown of Actual Building Delivered Energy (kWh) for Retail; Elec; MV – HP.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	7,613	0	9,892	19,441	2,051	-4,596	27.52	0.0%
Low	7,626	0	9,892	18,456	2,051	-28,146	7.90	71.3%
Med.	6,040	0	9,892	16,647	2,051	-112,585	-62.36	326.6%
High	4,598	0	9,892	15,367	2,051	-112,585	-64.54	334.5%

Table 55: Breakdown of Actual Building Delivered Energy (kWh) for Secondary School; DHN; AC.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	108,896	23,896	135,218	61,301	153,808	222,689	32.50	0.0%
Low	109,799	23,896	135,218	60,284	153,808	171,378	38.89	-19.7%
Med.	100,401	23,802	134,834	53,496	153,808	316,687	18.68	42.5%
High	82,837	19,943	131,076	49,504	153,808	310,709	15.78	51.4%

Table 56: Breakdown of Actual Building Delivered Energy (kWh) for Secondary School; Elec; MV – HP.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	57,664	620	60,315	61,301	91,288	58,432	26.55	0.0%
Low	57,944	620	60,315	60,284	91,288	171,250	12.38	53.4%
Med.	49,099	614	60,315	53,496	91,288	287,845	-4.12	115.5%
High	40,504	519	60,315	49,504	91,288	284,658	-5.31	120.0%

Table 57: Breakdown of Actual Building Delivered Energy (kWh) for Secondary School; Elec; NV – DE.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	232,216	565	90,280	61,301	131,336	291,753	27.95	0.0%
Low	233,028	565	90,280	60,284	131,336	168,873	43.26	-54.8%
Med.	229,303	558	90,280	53,496	131,336	330,195	21.81	22.0%
High	218,263	466	90,280	49,504	131,336	328,573	20.13	28.0%

Table 58: Breakdown of Actual Building Delivered Energy (kWh) for Warehouse Distribution; Elec; AC – HP.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	63,144	24,617	345,908	23,185	38,995	267,548	43.39	0.0%
Low	63,591	23,776	337,772	22,692	38,995	118,477	70.01	-61.3%
Med.	51,302	23,953	335,603	20,220	38,995	395,536	14.17	67.4%
High	42,709	18,157	292,158	18,695	38,995	375,762	6.64	84.7%

Table 59: Breakdown of Actual Building Delivered Energy (kWh) for Warehouse Distribution; Elec; MV – DE.

Opt.	Heating (kWh)	Cooling (kWh)	Aux. (kWh)	Light. (kWh)	DHW (kWh)	Useful PV output (kWh)	BDER (kWh/ m²)	Pass Margin (%)
BAU	347,910	0	41,242	23,185	79,214	288,542	38.58	0.0%
Low	349,958	0	41,242	22,692	79,214	118,477	71.20	-84.5%
Med.	339,355	0	41,242	20,220	79,214	309,471	32.42	16.0%
High	336,002	0	41,242	18,695	79,214	310,358	31.32	18.8%

Table 60: Delivered Energy and Emissions Rates for Shallow Office; DHN; NV.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	18.21	0.0%	0.00	1.86
Low	22.86	-25.5%	0.63	1.86
Medium	6.19	66.0%	-1.43	1.75
High	1.93	89.4%	-1.62	1.59

Table 61: Delivered Energy and Emissions Rates for Deep Office AC; Elec; AC – HP.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	28.50	0.0%	2.33	3.09
Low	26.93	5.5%	3.82	3.09
Medium	16.13	43.4%	2.41	2.94
High	13.30	53.3%	2.01	2.69

Table 62: Delivered Energy and Emissions Rates for Health centre; DHN; MV.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	12.86	0.0%	-0.02	2.68
Low	24.10	-87.4%	1.00	2.67
Medium	5.23	59.4%	-1.55	2.52
High	0.17	98.7%	-1.77	2.30

Table 63: Delivered Energy and Emissions Rates for Hotel; Elec; NV – DE.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	265.27	2.2%	0.46	22.81
Low	249.75	7.9%	35.84	22.80
Medium	231.66	14.6%	33.47	22.56
High	223.46	17.6%	32.23	21.86

Table 64: Delivered Energy and Emissions Rates for Retail; Elec; AC – HP.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	63.56	0.0%	2.98	6.20
Low	48.59	23.5%	6.87	6.12
Medium	-20.66	132.5%	-2.04	5.97
High	-25.30	139.8%	-2.67	5.57

Table 65: Delivered Energy and Emissions Rates for Retail; Elec; MV – HP.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	27.52	0.0%	0.65	2.68
Low	7.90	71.3%	1.43	2.62
Medium	-62.36	326.6%	-7.64	2.38
High	-64.54	334.5%	-7.96	2.20

Table 66: Delivered Energy and Emissions Rates for Secondary School; DHN; AC.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	32.50	0.0%	0.25	4.45
Low	38.89	-19.7%	4.18	4.45
Medium	18.68	42.5%	1.48	4.33
High	15.78	51.4%	1.29	4.14

Table 67: Delivered Energy and Emissions Rates for Secondary School; Elec; MV – HP.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	26.55	0.0%	0.54	2.91
Low	12.38	53.4%	2.04	2.90
Medium	-4.12	115.5%	-0.38	2.73
High	-5.31	120.0%	-0.57	2.60

Table 68: Delivered Energy and Emissions Rates for Secondary School; Elec; NV – DE.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	27.95	0.0%	0.16	5.54
Low	43.26	-54.8%	6.59	5.53
Medium	21.81	22.0%	3.61	5.42
High	20.13	28.0%	3.35	5.26

Table 69: Delivered Energy and Emissions Rates for Warehouse Distribution; Elec; AC – HP.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	43.39	0.0%	0.56	8.10
Low	70.01	-61.3%	10.08	7.96
Medium	14.17	67.4%	2.74	7.68
High	6.64	84.7%	1.56	6.71

Table 70: Delivered Energy and Emissions Rates for Warehouse Distribution; Elec; MV – DE.

Option	BDER (kWh/m²)	Delivered Energy Pass Margin (%)	BER (kgCO2/m²)	BER (proposed emission factors) (kgCO2/m²)
Baseline	38.58	0.0%	0.10	8.03
Low	71.20	-84.5%	11.01	8.06
Medium	32.42	16.0%	5.46	7.85
High	31.32	18.8%	5.29	7.77

4.1.1 Commentary on SBEM results

The results show the following key relationships:

For 6 of the 11 modelled building types, the low scenario is not compliant with the current Section 6 (2022) standard, with these buildings requiring a greater area of PV than is included in the low scenario, as is explained in Section 2.3.1. This is the case for following buildings:

• Shallow Office; DHN; NV
• Health centre; DHN; MV
• Secondary School; DHN; AC
• Secondary School; Elec; NV – DE
• Warehouse Distribution; Elec; AC – HP
• Warehouse Distribution; Elec; MV – DE

The low scenario specification is broadly similar to that of the current section 6 notional building, (see Section 3.2). There are a few differences between these two, some which reduce energy use (such as a 5% improvement in ASHP efficiency) and others that make it worse (such as a 25% increase in air-permeability and a 14% reduction in cooling efficiency). In addition to these small differences, there are differences between how the energy use of the notional and actual buildings is calculated. These differences are embedded within the NCM, the most significant of these relate to the calculation of auxiliary energy use for ventilation. Collectively these differences in specification and differences in calculation method result in 6 of the 11 archetypes failing to achieve compliance with the current regulation when the low scenario is adopted, as described above.

In considering this, it is helpful to note that, where the low scenario specification differs from the notional specification, these differences are primarily based on analysis of the EPC database to determine what the average specification is for each individual parameter (see Section 2.2). However, whilst it can be assumed that all the buildings in the EPC database achieved compliance, there may be very few of these which adopted the average (or close to the average) specification for all parameters. It is likely that the majority of buildings significantly differ from the average specification in one or more of the key areas of specification in order to achieve compliance.

The building types listed below achieve a greater pass margin in the low scenario than the baseline BAU scenario, as the area of PV required for these buildings to comply with Section 6 (2022) is less than the area included in the low scenario:

• Deep Office AC; Elec; AC – HP
• Hotel; Elec; NV – DE
• Retail; Elec; AC – HP
• Retail; Elec; MV – HP
• Secondary School; MV – HP

The improvements between the baseline and/or low scenarios are largely driven by the inclusion of a larger PV area, helping to offset a larger proportion of the buildings’ energy. A smaller contribution is made by other energy efficiency improvements.

The reduction in delivered energy between the medium and high scenarios are found to be smaller than between the baseline/low and medium scenarios, as illustrated in Figure 49. The reductions achieved between the medium and high scenarios result from energy efficiency improvements made to the building (other than increased PV area). The smallest improvement between the medium and high scenarios is observed for the Hotel; Elec; NV – DE and Warehouse Distribution; Elec; MV – DE buildings, both of which achieve a 3-percentage point improvement. The largest improvement between the medium and high scenarios is seen for the Heath centre; DHN; MV, which achieves a 39-percentage point improvement.

Two of the archetypes have direct electric combined with natural ventilation as the primary HVAC strategy, a Hotel and Secondary School. In these cases, it might be expected that the auxiliary energy (fans and pumps) would be zero, however this is not the case because, some areas have local extract and the high demand DHW systems in these buildings include a circulation loop with associated pump energy.

Similarly, the naturally ventilated secondary school has a small cooling demand because, although natural ventilation is the dominant HVAC system, the server room has cooling.

Comparing the three Secondary Schools it can be seen that the DHW energy demand is higher for the DHN heated scenario than it is for the direct electric scenario. This difference is due to the additional heat losses in the DHN DHW system associated with the secondary circulation loop and onsite storage tank. In comparison the direct electric DHW system is local instantaneous so has no additional heat losses, (see Table 41 on page 83).

For the naturally ventilated Hotel (Hotel; Elec; NV – DE), the modelled improvements do not impact the domestic hot water energy demand, which dominates the overall energy demand, and therefore limits the scope of improvement possible between the medium and high scenarios.

In a similar vein, the energy demands from the mechanically ventilated Distribution Warehouse (Warehouse Distribution; Elec; MV – DE) are dominated by the space heating demand. This building uses direct electric space heating, which means that there is a more limited scope to reduce the heating delivered energy demand, i.e., through fabric improvements. Conversely, improvements to the lighting and solar control performance of the building between the medium and high scenarios will act to increase the demand for space heating, as both measures reduce incidental gains into the building.

In the mechanically ventilated Health Centre (Heath centre; DHN; MV), although both of its space heating and domestic hot water demands are met by systems that cannot have their efficiencies directly improved (district heating and direct electric, respectively); overall, the building achieves the greatest percentage point improvement between the medium and high scenarios. The building is found to have a more even distribution between the different energy end-uses, especially compared to the previously described cases, allowing improvements in certain end-uses to contribute a greater proportion to the overall improvement. For this building, the modelled fabric improvements result in significant space heating savings, with comparable improvements also made in cooling and lighting energy performance. This contributes to the building achieving the greatest overall percentage point improvement between the medium and high scenarios.

In some buildings, the amount of useful PV generated electricity reduces between the medium and high scenarios, despite the PV area, and total PV electricity generation, remaining the same. This is because the energy efficiency measures reduce the energy consumption of the building, and therefore less of the PV generated electricity is deemed to be “useful”, i.e. able to be used on site following the definition described in the NCM modelling guide.

4.2 PHPP results

4.2.1 Delivered Energy Summary

Table 71 - Table 81 show the delivered energy [kWh/m²/yr] summary generated using PHPP v10.6^[[5]][[6]].

Table 71. Delivered Energy [kWh/m²/yr] - ShOffice AC/ DHN/ NV.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	32.76	0.0%
2 - Low	37.02	-13.0%
3 - Medium	19.67	40.0%
4 - High	12.86	60.8%

Table 72. Delivered Energy [kWh/m²/yr] – DpOffice AC/Elec/HP.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	19.19	0.0%
2 - Low	25.93	-35.1%
3 - Medium	14.26	25.7%
4 - High	9.00	53.1%

Table 73. Delivered Energy [kWh/m²/yr] – HealthCtr DHN/MV.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	15.14	0.0%
2 - Low	24.15	-59.5%
3 - Medium	4.29	71.7%
4 - High	-2.98	119.7%

Table 74. Delivered Energy [kWh/m²/yr] – Hotel NV/DE.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	228.16	0.0%
2 - Low	209.32	8.3%
3 - Medium	192.43	15.7%
4 - High	183.21	19.7%

Table 75. Delivered Energy [kWh/m²/yr] – Retail AC/HP.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	36.07	0.0%
2 - Low	21.84	39.4%
3 - Medium	-51.39	242.5%
4 - High	-54.83	252.0%

Table 76. Delivered Energy [kWh/m²/yr] – Retail MV/HP.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	26.35	0.0%
2 - Low	5.71	78.3%
3 - Medium	-67.44	355.9%
4 - High	-69.43	363.5%

Table 77. Delivered Energy [kWh/m²/yr] – SecSchool AC/DHN.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	13.01	0.0%
2 - Low	18.11	-39.2%
3 - Medium	-4.92	137.8%
4 - High	-9.90	176.1%

Table 78. Delivered Energy [kWh/m²/yr] – SecSchool MV/HP.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	19.77	0.0%
2 - Low	-2.68	113.6%
3 - Medium	-21.61	209.3%
4 - High	-23.38	218.3%

Table 79. Delivered Energy [kWh/m²/yr] – SecSchool NV/DE.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	31.91	0.0%
2 - Low	44.65	-39.9%
3 - Medium	20.82	34.8%
4 - High	14.91	53.3%

Table 80. Delivered Energy [kWh/m²/yr] – Dware AC/HP.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	-1.47	0.0%
2 - Low	11.10	855.5%
3 - Medium	-50.02	-3304.7%
4 - High	-48.48	-3199.4%

Table 81. Delivered Energy [kWh/m²/yr] – Dware MV/DE.

Case	BDER (kWh/m2/yr)	Delivered Energy Pass Margin (%)
1 - BAU	20.31	0.0%
2 - Low	38.41	-89.1%
3 - Medium	-9.97	149.1%
4 - High	-16.30	180.3%

4.2.2 Key PHPP Variations

Figure 50 to Figure 58 present the Energy Balance for Simulations 1-4 (1‑BAU, 2‑Low, 3‑Medium, and 4‑High) for three representative building sub-types: 04 Hotel NV DE, 01 ShOffice NV, and 07 SecSchool AC. These cases were selected to illustrate contrasting performance trends between the PHPP and SBEM models.

• For 04 Hotel NV DE, the Space Heating (SH) demand predicted by PHPP was 46-53% lower than SBEM across all four simulation scenarios (45.99%, 49.14%, 47.92%, 53.14% for Sim 1-4 respectively). Similarly, the Space Cooling (SC) demand was 73-78% lower (74.14%, 73.16%, 73.71%, 78.73% for Sim 1-4 respectively).
• For 01 ShOffice NV, the opposite pattern is observed: PHPP predicts higher Space Heating (SH) demand compared to SBEM - by approximately 58-65% across the four simulations (60.3%, 58.37%, 64.39%, 65.02% higher for Sim 1-4, respectively). Space Cooling (SC) demand in PHPP is slightly lower, by 5-13% (6.05%, 5.17%, 8.64%, 13.36% lower for Sim 1-4, respectively).
• For 07 SecSchool AC, the Space Heating (SH) demand predicted by PHPP is within approximately 12–63% of the SBEM values across the four simulations (12.46%, 30.88%, 28.7%, and 62.69% higher in PHPP for Sim 1–4, respectively).

A discussion and interpretation of these findings is provided in Section 4.2.3. Table 82 to Table 84 present the space cooling (SC) and space heating (SH) results for Simulations 1-4 for the selected cases listed below. The full set of figures for all eleven-building sub‑types are included in Appendix E for reference.

Table 82: Space Heating (SH) & Space Cooling (SC) for 04 Hotel NV DE.

Run	Data	Units	SBEM	PHPP
Sim 1	SH Demand	kWh/m²·yr	81.7	44.13
Sim 1	SC Demand	kWh/m²·yr	36.68	9.49
Sim 2	SH Demand	kWh/m²·yr	81.81	41.61
Sim 2	SC Demand	kWh/m²·yr	36.52	9.8
Sim 3	SH Demand	kWh/m²·yr	79.89	41.61
Sim 3	SC Demand	kWh/m²·yr	36.56	9.61
Sim 4	SH Demand	kWh/m²·yr	72.17	33.82
Sim 4	SC Demand	kWh/m²·yr	32.78	6.97

Table 83: Space Heating (SH) & Space Cooling (SC) for 01 ShOffice NV.

Run	Data	Units	SBEM	PHPP
Sim 1	SH Demand	kWh/m²·yr	23.33	37.4
Sim 1	SC Demand	kWh/m²·yr	26.86	25.24
Sim 2	SH Demand	kWh/m²·yr	23.33	36.95
Sim 2	SC Demand	kWh/m²·yr	26.86	25.48
Sim 3	SH Demand	kWh/m²·yr	22.48	36.95
Sim 3	SC Demand	kWh/m²·yr	26.98	24.65
Sim 4	SH Demand	kWh/m²·yr	19.03	31.4
Sim 4	SC Demand	kWh/m²·yr	25.36	21.97

Table 84: Space Heating (SH) & Space Cooling (SC) for 07 SecSchool AC.

Run	Data	Units	SBEM	PHPP
Sim 1	SH Demand	kWh/m²·yr	9.75	8.54
Sim 1	SC Demand	kWh/m²·yr	15.26	3.01
Sim 2	SH Demand	kWh/m²·yr	9.75	6.74
Sim 2	SC Demand	kWh/m²·yr	15.26	3.25
Sim 3	SH Demand	kWh/m²·yr	8.6	6.13
Sim 3	SC Demand	kWh/m²·yr	15.21	3.15
Sim 4	SH Demand	kWh/m²·yr	6.24	2.33
Sim 4	SC Demand	kWh/m²·yr	13.9	2.53

4.2.3 Commentary on PHPP results

As can be seen in 4.2.1, the PHPP and SBEM comparison are consistent with those reported in section 2.4.3 for the BAU models. This indicates that PHPP and SBEM agree on the direction and magnitude of changes to energy consumption arising from changes in specification. As such, if used as a compliance tool to assess compliance against a notional building specification target, it is possible that PHPP may offer a similar outcome to SBEM. However, the issues raised around the use of PHPP for compliance in section 2.4.4 do still apply as there are specific areas of building energy consumption, such as heating, cooling and auxiliary systems, that still appear to be significantly different to SBEM.

It is important to note that much of the functionality of PHPP has been removed to align with the SBEM modelling inputs (i.e. to make PHPP and SBEM model the exact same building). PHPP would offer significantly different results if the additional data and calculations were utilised. For example, modelling of actual DHW pipework losses and HVAC duct heat losses and predicted system efficiencies would yield very different and arguably more accurate results. In addition, the PHPP certifiable default figure for internal gains was significant below the NCM gains rates for all models.

The results indicate that the building physics of the PHPP model does align closely enough with SBEM to predict a similar level of impact for individual and grouped specification changes. Therefore, it is likely that this would also be the case for the PHPP model that has been populated in line with PHPP conventions. This means that a potentially more accurate model, which is used to assess compliance with PH targets for energy consumption and space heating/cooling demand, could offer a robust comparison against a notional performance standard. For example, SBEM and PHPP may disagree on the total energy consumption of a building; however, this study suggests that they may agree on the percentage improvement that differences to a notional specification would yield. In the case of auxiliary energy, where we understand that PHPP predicts lower energy consumption rates than SBEM, both the notional and actual auxiliary energy consumption rates would be low, resulting in a similar percentage improvement or shortfall to that reported in SBEM.

Further work may be able to better identify why PHPP and SBEM differ more significantly for specific energy consumption rates. If methods to reduce this difference were developed, then this could further strengthen the case for using PHPP as a compliance model as well as a model for assessing performance against absolute targets. This work may be challenging due to the wide range of building typologies that Section 6 is required to regulate. It is also important to consider PHPP’s validity and accuracy for building typologies which are less commonly assessed (i.e. distribution warehouses and hotels). Less common typologies have fewer project examples to validate that PHPP performance aligns with empirical energy usage. Furthermore, more unique non-domestic buildings may have more significant differences to the NCM activity database assumptions. In these scenarios, the PHPP approach of modelling the actual building equipment use and occupancy profiles may begin to drive differences with SBEM simply due to the standardised approach of the NCM differing to the reality. In this situation PHPP would be more robust for the assessment of absolute targets but could be less robust for the comparison against a notional performance target.

In summary, it is evident that PHPP and SBEM generally agree on the impact of specification changes for non-domestic buildings, when an aligned modelling approach is applied. Further evidence would be required to demonstrate that the use of full PHPP conventions would agree to the same extent across a broad range of building types. PHPP offers a more detailed and likely more accurate methodology for assessing performance against absolute targets but may not be appropriate for use as a compliance model against a set notional performance standard for all possible non-domestic buildings; however, for some more commonly occurring and well validated building typologies there could be some opportunity to use PHPP in place of SBEM.

Scottish government would need to consider carefully the approach to using PHPP as a compliance model for Section 6. The analysis has shown that, for certain typologies, the BAU specification can comply with absolute target of 15kWh/m²/yr for space heating and cooling, although it should be noted that this would only be the case if the NCM gains assumptions were applied. Therefore, the Scottish Government may need to consider if there is a risk that absolute targets for all building typologies might result in lower standards of specification on specific building typologies, this is discussed further in Section 3.3.2. For many of the building typologies assess, absolute targets would significantly improve standards beyond those modelled as best practice in this study.

4.3 Cost modelling

The SBEM modelling results were used to assess the benefits at a national level. The 11 sample buildings and annual build numbers used for the baseline were also used in the counterfactual scenarios, and these were assumed to be unchanged over the analysis period.

4.3.1 Transitional Period

The national profile modelling assumes a transitional period as new standards are introduced (i.e. not all buildings built in 2026 will be to 2026 standards). The assumptions made were agreed with Scottish Government and are set out in Table 85.

Table 85: Transitional period assumptions for 2026 standards.

Proportions of new non-domestic buildings built to relevant standard in each year	2028	2029	2030	2031	2032 onwards
2021 standard	80%	60%	40%	20%	0%
2026 standard	20%	40%	60%	80%	100%

Source: Agreed with Scottish Government.

4.4 National Impacts (benefits)

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 4.1 were applied to the national build profile, taking into account the assumptions on build/fuel mix and build rates set out in Section 2.1.

A 25-year analysis period was used. The three counterfactual cases (“Low”, “Medium” and “High”) were compared to the 2021 compliant base case. The carbon emission factors applied for gas and electricity are those published by DESNZ to support the HM Treasury Green Book supplementary appraisal guidance on valuing energy use and greenhouse gas (GHG) emissions (DESNZ, 2023). The factors for electricity are projected to decrease over time and are summarised in Table 86. The factor for gas is 0.184 kgCO₂e/kWh. The Green Book does not include a carbon emission factor or cost for heat networks, the value proposed this analysis is based on the assumption of heat networks having a carbon factor of 0.034 kgCO₂/kWh.

Table 86: Carbon emission factors used in benefit analysis – electricity (kgCO₂e/kWh).

Year	Consumption	Generation
2026	0.187	0.174
2027	0.166	0.154
2028	0.143	0.133
2029	0.118	0.110
2030	0.091	0.085
2031	0.070	0.065
2032	0.054	0.050
2033	0.041	0.038
2034	0.032	0.029
2035	0.024	0.023
2036	0.019	0.017
2037	0.014	0.013
2038	0.011	0.010
2039	0.008	0.008
2040	0.006	0.006
2041	0.006	0.006
2042	0.004	0.004
2043	0.003	0.003
2044	0.002	0.002
2045	0.001	0.001
2046	0.001	0.001
2047	0.001	0.001
2048	0.002	0.001
2049	0.001	0.001
2050	0.001	0.001

Source DESNZ, 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) (DESNZ, 2023).

The results by year are presented in Table 86. 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 88. This shows that the “Low”, “Medium” and “High” cases are estimated to achieve a -0.7%, 10.1% and 11.4% reduction in carbon emissions compared to the base case respectively.

Table 87: Annual carbon emissions for base case and counterfactual cases (ktCO2e/yr).

Year	Baseline: 1-BAU	2-Low	3-Medium	4-High
2026	9.4	9.4	9.4	9.4
2027	17.7	17.7	17.7	17.7
2028	24.9	24.9	24.5	24.4
2029	30.8	30.9	29.7	29.6
2030	35.4	35.5	33.5	33.3
2031	39.0	39.1	36.3	35.9
2032	41.7	41.9	38.2	37.8
2033	43.8	44.1	39.7	39.3
2034	45.5	45.8	41.0	40.4
2035	46.7	47.1	41.8	41.3
2036	47.7	48.1	42.6	42.0
2037	48.5	48.9	43.2	42.5
2038	49.1	49.5	43.6	42.9
2039	49.6	50.0	43.9	43.2
2040	49.9	50.3	44.2	43.5
2041	50.3	50.7	44.5	43.7
2042	50.5	51.0	44.7	43.9
2043	50.8	51.2	44.8	44.0
2044	50.9	51.3	44.9	44.1
2045	51.0	51.4	45.0	44.2
2046	51.1	51.6	45.1	44.3
2047	51.3	51.7	45.2	44.4
2048	51.4	51.8	45.4	44.5
2049	51.5	52.0	45.5	44.6
2050	51.7	52.1	45.6	44.7
Total	1,090.3	1,098.0	980.0	965.7

Table 88: Total carbon emissions for counterfactual cases.

Scenario	Total carbon saving (ktCO2e/yr)	% reduction compared to base case
2- Low	-7.7	-0.7%
3- Medium	110.3	10.1%
4- High	124.6	11.4%

4.5 National impacts (costs)

The capital costs (in 2025 prices) of each building type for the 2021, low, medium and high cases, are shown in Table 89 to

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	2,785,734	34,734	503,743	429,336	5,717,458	9,471,006	0%
Option 1 - low	2,785,734	34,734	503,743	190,122	5,717,458	9,231,791	-3%
Option 2 - medium	2,796,257	34,734	561,619	678,676	5,717,458	9,788,744	3%
Option 3 - high	2,950,700	35,292	751,036	678,676	5,717,458	10,133,161	7%

Table 89: Capital costs (£) by case and fuel type – Shallow Office, NV, DHN.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	784,630	63,036	163,620	68,147	4,320,567	5,400,000	0%
Option 1 - low	784,630	63,036	163,620	52,032	4,320,567	5,383,885	0%
Option 2 - medium	788,950	63,036	185,220	104,064	4,320,567	5,461,837	1%
Option 3 - high	802,630	63,036	260,820	104,064	4,320,567	5,551,117	3%

Table 90 : Capital costs (£) by case and fuel type – Deep Office AC; Elec; AC – HP.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	2,644,651	2,115,406	1,377,417	143,213	35,719,314	42,000,000	0%
Option 1 - low	2,644,651	2,115,406	1,377,417	173,440	35,719,314	42,030,227	0%
Option 2 - medium	2,668,651	2,233,597	1,520,837	346,880	35,719,314	42,489,279	1%
Option 3 - high	2,734,151	2,749,821	1,964,258	346,880	35,719,314	43,514,424	4%

Table 91 : Capital costs (£) by case and fuel type – Health Centre; MV; DHN.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	1,078,040	55,789	222,421	114,743	7,506,507	8,977,500	0%
Option 1 - low	1,078,040	55,789	222,421	72,086	7,506,507	8,934,843	0%
Option 2 - medium	1,082,030	55,789	245,936	169,152	7,506,507	9,059,415	1%
Option 3 - high	1,098,251	55,789	319,326	169,152	7,506,507	9,149,026	2%

Table 92: Capital costs (£) by case and fuel type – Hotel, NV – DE.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	495,713	20,676	80,503	0	2,591,358	3,188,250	0%
Option 1 - low	495,713	20,676	80,503	26,182	2,591,358	3,214,432	1%
Option 2 - medium	497,838	20,676	91,131	52,364	2,591,358	3,253,367	2%
Option 3 - high	505,349	20,676	128,327	52,364	2,591,358	3,298,074	3%

Table 93: Capital costs (£) by case and fuel type – Retail, Elec, AC – HP.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	1,037,563	223,905	134,028	17,067	1,464,494	2,877,057	0%
Option 1 - low	1,037,563	223,905	134,028	45,167	1,464,494	2,905,157	1%
Option 2 - medium	1,040,063	236,217	148,495	180,667	1,464,494	3,069,935	7%
Option 3 - high	1,054,063	288,392	194,212	180,667	1,464,494	3,181,828	11%

Table 94 : Capital costs (£) by case and fuel type – Retail, Elec, MV – HP.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	1,048,063	96,039	134,028	7,376	1,464,494	2,750,000	0%
Option 1 - low	1,048,063	96,039	134,028	45,167	1,464,494	2,787,791	1%
Option 2 - medium	1,050,563	98,598	148,495	180,667	1,464,494	2,942,817	7%
Option 3 - high	1,064,663	110,310	194,212	180,667	1,464,494	3,014,346	10%

Table 95: Capital costs (£) by case and fuel type – Secondary School, DHN, AC.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	3,760,296	876,947	1,255,227	383,962	18,927,055	25,203,487	0%
Option 1 - low	3,760,296	876,947	1,255,227	289,517	18,927,055	25,109,042	0%
Option 2 - medium	3,776,321	876,947	1,367,766	632,911	18,927,055	25,581,001	1%
Option 3 - high	3,839,383	878,498	1,680,619	632,911	18,927,055	25,958,467	3%

Table 96 : Capital costs (£) by case and fuel type – Secondary School, Elec, MV – HP.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	3,760,296	536,377	1,255,227	93,766	18,927,055	24,572,721	0%
Option 1 - low	3,760,296	536,377	1,255,227	289,517	18,927,055	24,768,473	1%
Option 2 - medium	3,776,321	550,295	1,367,766	632,911	18,927,055	25,254,349	3%
Option 3 - high	3,839,383	613,983	1,680,619	632,911	18,927,055	25,693,952	5%

Table 97: Capital costs (£) by case and fuel type – Secondary School, Elec, NV – DE.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	3,849,634	132,250	606,951	521,761	18,927,055	24,037,650	0%
Option 1 - low	3,849,634	132,250	606,951	289,517	18,927,055	23,805,407	-1%
Option 2 - medium	3,865,659	132,250	687,076	632,911	18,927,055	24,244,952	1%
Option 3 - high	3,943,015	132,250	967,515	632,911	18,927,055	24,602,747	2%

Table 98: Table 98: Capital costs (£) by case and fuel type – Warehouse Distribution, Elec, AC – HP.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	2,785,734	34,734	503,743	429,336	5,717,458	9,471,006	0%
Option 1 - low	2,785,734	34,734	503,743	190,122	5,717,458	9,231,791	-3%
Option 2 - medium	2,796,257	34,734	561,619	678,676	5,717,458	9,788,744	3%
Option 3 - high	2,950,700	35,292	751,036	678,676	5,717,458	10,133,161	7%

Table 99 : Capital costs (£) by case and fuel type – Warehouse Distribution, Elec, MV – DE.

Category	Fabric	Heating and cooling	Lighting and ventilation	Photo-voltaics	Balance of construction cost	Total	Uplift on 2021
BS2021	2,788,984	110,732	503,743	578,695	5,717,458	9,699,612	0%
Option 1 - low	2,788,984	110,732	503,743	190,122	5,717,458	9,311,039	-4%
Option 2 - medium	2,799,507	110,732	561,619	678,676	5,717,458	9,867,992	2%
Option 3 - high	2,954,470	110,732	751,036	678,676	5,717,458	10,212,372	5%

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^[8] 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 secondary school for the different cases is shown in Table 100 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 100: Potential variation in build costs for non-domestic buildings built in the Western Isles – Secondary School, Elec, MV – HP.

Scenario	Central cost	Cost for projects in Western Isles	Variation in overall cost from base specification in Western Isles
Base	9,471,006	£12,312,308	£0
Low	9,082,433	£11,807,163	-£505,145
Medium	9,639,386	£12,531,202	£218,894
High	9,983,766	£12,978,896	£666,588

The capital, maintenance and renewal, energy (variable cost) and lifetime costs of each case and fuel type are shown in Table 101. These costs are the net present value costs over a 60-year period for a building constructed in 2026 (in 2025 prices). Information is presented for each building type against the relevant 2021 base case specification and fuel type. Lifetime energy costs are derived from energy price projections published by DESNZ, renewal and maintenance costs are derived on an elemental basis in line with the assumptions in Appendix D. Renewal and maintenance costs reflect only those elements that are linked to the variations in specification and exclude common elements that are consistent between each option, for example district heat network connections (for relevant buildings) or hot water generation and distribution.

Table 101: Lifetime costs by building, case and heating type (£ present value per building) - Deep Office AC; HP.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	£27,994	-£287,036	£8,557	£0	-£250,485
Option 2 - med	£460,712	-£2,439,205	£314,308	£49,573	-£1,614,612
Option 3 - high	£1,437,663	-£3,239,014	£1,298,517	£141,430	-£361,404

Table 102. Lifetime costs by building, case and heating type (£ present value per building) - Shallow office, NV, DHN.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£14,925	£259,688	-£4,562	£0	£240,201
Option 2 - med	£57,611	-£679,196	£27,728	£0	-£593,857
Option 3 - high	£141,437	-£809,907	£92,035	£0	-£576,434

Table 103. Lifetime costs by building, case and heating type (£ present value per building) - Hotel; NV, DE.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	£24,248	-£1,883,117	£7,412	£0	-£1,851,456
Option 2 - med	£60,476	-£4,246,358	£23,464	£0	-£4,162,418
Option 3 - high	£102,473	-£5,776,755	£55,136	£0	-£5,619,146

Table 104. Lifetime costs by building, case and heating type (£ present value per building) - Healthcare, MV, DHN.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£39,506	£814,999	-£12,076	£0	£763,417
Option 2 - med	£76,323	-£1,218,594	£33,900	£15,389	-£1,092,981
Option 3 - high	£160,655	-£1,417,435	£97,600	£30,778	-£1,128,402

Table 105. Lifetime costs by building, case and heating type (£ present value per building) - Retail; AC, HP.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	£26,024	-£938,834	£7,955	£0	-£904,855
Option 2 - med	£179,401	-£5,193,266	£72,748	£13,250	-£4,927,868
Option 3 - high	£286,101	-£5,627,514	£178,057	£29,755	-£5,133,600

Table 106. Lifetime costs by building, case and heating type (£ present value per building) - Retail; MV, HP.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	£34,999	-£1,617,417	£10,699	£0	-£1,571,720
Option 2 - med	£178,954	-£7,407,352	£62,502	£17,639	-£7,148,257
Option 3 - high	£246,655	-£7,678,792	£113,730	£35,278	-£7,283,129

Table 107. Lifetime costs by building, case and heating type (£ present value per building) - Distribution, AC, HP.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£221,545	£2,708,437	-£67,722	£0	£2,419,171
Option 2 - med	£295,313	-£3,912,552	£116,724	£14,640	-£3,485,875
Option 3 - high	£622,152	-£5,750,923	£375,663	£30,832	-£4,722,275

Table 108. Lifetime costs by building, case and heating type (£ present value per building) - Distribution, MV, DE.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£359,871	£2,535,310	-£110,005	£0	£2,065,434
Option 2 - med	£156,987	-£830,493	£74,441	£7,573	-£591,493
Option 3 - high	£483,790	-£908,605	£333,435	£15,145	-£76,235

Table 109. Lifetime costs by building, case and heating type (£ present value per building) - Secondary School, AC, DHN.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£87,469	£401,401	-£26,738	£0	£287,194
Option 2 - med	£352,197	-£1,193,791	£156,331	£31,344	-£653,921
Option 3 - high	£707,866	-£1,370,442	£423,623	£64,188	-£174,764

Table 110. Lifetime costs by building, case and heating type (£ present value per building) - Secondary School, MV, HP.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	£181,292	-£1,922,555	£55,417	£0	-£1,685,846
Option 2 - med	£634,405	-£5,641,413	£249,494	£70,305	-£4,687,210
Option 3 - high	£1,050,110	-£5,947,437	£566,168	£140,610	-£4,190,549

Table 111. Lifetime costs by building, case and heating type (£ present value per building) - Secondary School NV, DE.

Building type and case	Change in capital cost	Change in energy cost	Change in renewals cost	Change in maintenance cost	Change in lifetime cost
Option 1 - low	-£215,089	£929,076	-£65,748	£0	£648,239
Option 2 - med	£193,259	-£552,228	£96,606	£0	-£262,362
Option 3 - high	£529,923	-£702,579	£353,499	£0	£180,843