Building regulations - proposed changes to energy and environmental standards: stage 2 consultation and BRIA

6 New non-domestic buildings

6.1 Level of challenge for new non-domestic buildings

The February 2023 energy standards introduced a level of challenge for new non-domestic buildings with an aggregate reduction in carbon emissions of 16% over the 2015 standards. This level of challenge is implemented through the Target Delivered Energy Rate (TDER): set based on a specification linked to the choice of main heating fuel type.

Through 2025, the Scottish Government carried out detailed modelling to determine whether an uplift in performance standards for new non-domestic buildings is reasonable and the options available at which the level of challenge could be set for implementation.

The modelling, undertaken by the Scottish Government’s technical consultant, considered four levels of building specification:

• As defined by the 2023 notional building
• Low level of challenge
• Medium level of challenge – Option 1
• High level of challenge – Option 2

Two modelling packages were utilised in the research to allow comparison of results:

• Simplified Building Energy Model v 6.1
• Passivhaus Planning Package (PHPP) version 10.6.

6.1.1. Proposals

Following discussion with the Technical Working Group Option 1 and Option 2 are applied and indicated for consultation alongside an option to retain the current 2023 level of challenge (Option 3).

Table 6 presents the proposed annual abatement in carbon emissions compared to the 2023 standards for Option 1 and Option 2 as calculated in SBEM v6.1 noting that retaining the current 2023 level of challenge results in a 0% annual abatement.

Table 6: New non-domestic buildings – annual carbon emissions abatement compared to the 2023 energy standards – proposed reduction as modelled in SBEM v6.1

New Non-Domestic Buildings	Option 1 – Medium	Option 2 – High
Annual abatement (%)	10%	11.5%
Annual abatement (kT)	6.2 kt CO2e	8.2 kt CO2e

Please refer to the associated published research piece for full details of the target setting specifications used to generate the potential reductions in carbon emissions presented above: ‘Improvements to Energy Standards for New Buildings within Scottish Building Regulations 2025: Modelling Report – Non-Domestic’.

The main elements are presented in table 7.

As reflected in the full non-domestic report, a Low Option was modelled. Given that this results in an increase in energy use and emissions across the modelled building stock, this has not been presented as an option for consultation, however, an option to retain the current February 2023 energy standards is presented.

Table 7: Options for uplift in the level of challenge for new non-domestic buildings.

Fabric	Option 3	Option 1 - Medium	Option 2 - High
External Wall U-value (W/m2K)	0.15	0.15	0.15
Floor U-value (W/m2K)	0.13	0.13	0.12
Roof U-value (W/m2K)	0.11	0.11	0.10
Window and glazed door U-value (W/m2K)	1.2	1.2	0.8
Window and glazed door g-value	0.50	0.50	0.40
Air permeability (m3/(h.m2) @50Pa)	4	4	3
Ventilation and pumps	Option 3	Option 1 - Medium	Option 2 - High
Central ventilation SFP (W/l/s)	1.80	1.80	1.80
Terminal unit SFP (W/l/s)	0.30	0.30	0.30
Ventilation heat recovery (%)	76	80	85
Demand control ventilation	Demand control of ventilation through variable fan speed control based on CO2 sensors	Demand control of ventilation through variable fan speed control based on CO2 sensors	Demand control of ventilation through variable fan speed control based on CO2 sensors
Variable speed pumping	Variable speed pumping with multiple pressure sensors in the system	Variable speed pumping with multiple pressure sensors in the system	Variable speed pumping with multiple pressure sensors in the system
Lighting	Section 6 2028 Option 3	Section 6 2028 Option 2 - Medium	Section 6 – 2028 Option 3 - High
Efficacy (llm/cW)	95	110	125
Occupancy control	Manual-On-Auto-Off	Manual-On-Auto-Off	Manual-On-Auto-Off
Daylight control	All rooms that receive daylight directly (i.e. have an external window)	All rooms that receive daylight directly (i.e. have an external window)	All rooms that receive daylight directly (i.e. have an external window)
Heating and hot water – heat pump	Option 3	Option 1 - Medium	Option 2 - High
System	Air source heat pump	Air source heat pump	Air source heat pump
Heating efficiency (%)	300% Flow temperature at 55oC	363% Flow temperature between 50oC and 55oC	410% Flow temperature at 45oC
Hot water efficiency (%) high demand	270%	325%	325%
Hot water efficiency (%) low demand	100% point of use	100% point of use	100% point of use
Heating and hot water – heat network	Option 3	Option 1 - Medium	Option 2 - High
System	Gas boiler	Heat network	Heat network
Heating efficiency (%)	93%	As actual building (100%)	As actual building (100%)
Hot water efficiency (%) high demand	93%	As actual building (100%)	As actual building (100%)
Hot water efficiency (%) low demand	100% point of use	100% point of use	100% point of use
Heating and hot water – any other solution	Option 3	Option 1 - Medium	Option 2 - High
System	Gas boiler	Direct electric	Direct electric
Heating efficiency (%)	93%	100%	100%
Hot water efficiency (%) high demand	93%	100% point of use	100% point of use
Hot water efficiency (%) low demand	100% point of use	100% point of use	100% point of use
Cooling	Option 3	Option 1 - Medium	Option 2 - High
Seasonal Energy Efficiency Ratio	6.4	5.5	6.0
Onsite generation of power – photovoltaics	Option 3	Option 1 - Medium	Option 2 - High
PV Area	The lesser sum of 15% x GIA Or 30% x foundation area With heat pump modification	30% x foundation area For all heat solutions	60% x foundation area For all heat solutions

The February 2023 standards introduced a step change in the performance of new non-domestic buildings with the research associated with the current review indicating that improvements in most measures that result in lower energy buildings would not be cost effective to introduce at this time.

However, the slight modifications in services efficiencies do reflect more closely the development in technology over the past few years.

Consultation Question 15

Do you have any comments on the cooling efficiency proposals across the Medium and High options noting that these represent a relaxation in the level of challenge for this element?

Yes

No

Please provide a summary of the reason(s) for your view.

Consultation Question 16

What level of uplift to the current energy standards for new non-domestic buildings do you consider should be introduced as an outcome of this review?

Option 1: ‘Medium’ standard (10% emissions reduction)

Option 2: ‘High’ standard (11.5% emissions reduction)

Option 3: Retain current standard (0% emissions reduction)

Other (please specify)

Please provide a summary of the reason(s) for your view.

For new buildings connecting to a communal heating system

Consultation proposals maintain the current option of three building specifications based on the heat source: heat pumps, heat networks and any other solution, the latter being assessed against the direct electric heating specification.

It is proposed, where buildings on a development are supplied from a communal heating system (as defined in the Heat Networks (Scotland) Act 2021), also located within the development, that the use and benefit of high efficiency generation on site should be recognised.

This would be achieved by enabling buildings supplied from such a communal heating system to be modelled against the heat pump notional building, with the net efficiency of communal heat supply determined by a suitably qualified party and input into the calculation.

Such an option will support the use of high-efficiency communal heating systems which give an overall delivered energy outcome for the development broadly similar to the use of individual heat pumps.

Consultation Question 17

Do you support an approach to enable recognition of higher efficiency generation within a development regardless of whether it takes place within individual buildings or is communal?

Yes

No

Please provide a summary of the reason(s) for your view.

6.2 Method of target setting for new non-domestic buildings

Standard 6.1 aims to limit the delivered energy needed at a new building to meet energy demand through the setting of an overall performance target calculated by an approved methodology.

Designers should demonstrate that the calculated Building Delivered Energy Rate (BDER) for the actual building does not exceed the Target Delivered Energy Rate (TDER). The TDER is calculated by a ‘notional building’ generated automatically by applying the National Calculation Methodology (NCM) for Scotland. The notional building has several items that are the same as the actual building (target fluctuating elements) and items that are fixed i.e. are not the same as the actual building (target fixing elements).

When a given building specification is fully defined and is modelled in the approved methodology a single BDER and a single TDER will be reported.

Note that given the proposal in section 2 of this consultation the following section should also be read noting the intent to introduce a space heating demand target alongside retaining the delivered energy demand target.

Target fixed elements

If a given building specification is modified there are a number of building specification elements that do not result in the TDER fluctuating. For example, the TDER for a given building specification does not consider the actual building fabric U-values as these are ‘fixed’ by the notional building i.e. at 0.15 W/m²K for walls. When everything else within a given building specification remains the same the infinite choice of fabric U-values should always result in a single TDER as the BDER fluctuates. This principle is the same for all elements of the notional building with a stated value in Table 6.1 of the current non-domestic building standards technical handbook and stated figures or action in the NCM.

Target fluctuating elements

If a given building specification is modified there a number of building specification elements that allow the TDER to fluctuate. For example, the TDER for a given building specification will be modified based on the orientation, conditioning strategy and zone activities defined in the actual building. This principle is the same for all elements of the notional building where the specification item is defined as the ‘same as the actual building’ or similar phrase within Table 6.1 of the current non-domestic building standards technical handbook and stated figures or action in the NCM.

Passivhaus

The Passivhaus system does not use a notional building approach, instead a single ‘absolute’ target must be met for total energy use and space heating demand. Where this single target is set, it is in effect ‘fixing’ all elements of the notional building on a single building specification that results in those targets being met. There are no notional building aspects that are defined as the same as the actual building. This means that any modification to the actual building specification does not modify the ‘absolute’ targets that need to be met.

6.2.1. Proposals

The Scottish Government proposes to limit the number of elements that allow the TDER to fluctuate within a target setting building to a number of clearly defined principles. These are:

• Building location;
• Building type (as defined in Table 1 of the SBEM technical manual);
• Activity type (as defined in Table 2 of the SBEM technical manual);
• Building orientation; and
• Building heat source

Building location

It is proposed that the target setting building location is set as the actual building dwelling location. For a given building specification this will produce a range of TDERs, the range being determined by the number of climate data files within the compliance methodology.

Scottish building regulations currently apply limited climate data set within the non-domestic calculation methodologies. Responses within the stage one consultation were in favour of a move to adopt regional climate data to enable a more informed approach to building design and reporting on performance which better reflects the impact of location on the building. Given this response we have implemented the use of available climate data within the consultation version of the non-domestic tool.

The final version of the tools will implement the 14 weather files available from CIBSE 2025 (or a more appropriate updated set). Given the proposal to allow the TDER to fluctuate based on the building location this will result in a range of TDERs determined by these 14 locations.

Building type

It is proposed that the target setting building type, as defined within Table 1 of the SBEM technical manual, is set as the actual building type. For a given building specification this will produce a range of TDERs, the range being determined by the 22 available building types.

Activity type

It is proposed that the target setting activity type, as defined within Table 2 of the SBEM technical manual, is set as the actual activity type. For a given building specification this will produce a range of TDERs, the range being determined by the mix of available activity types.

Building orientation

It is proposed that the target setting building orientation is set as the actual building orientation. For a given building specification this will produce a range of TDERs, the range being determined by the 360 degrees that are available for building placement.

Building heat source

It is proposed that the target setting building heat source is set as the actual building heat source. For a given building specification this will produce a range of TDERs, the range being determined by the three available heat options: heat pumps, heat networks and any other solution (direct electric).

It is proposed that all other building specification items will be ‘fixed’ within a target setting building.

Consultation Question 18

Do you agree with the proposal to allow the building target rates to fluctuate based only on the location, building type, activity types, heat source and orientation of the new building?

Yes

No

Please provide a summary of the reason(s) for your view.

When the TDER is only allowed to fluctuate depending on the limited items proposed and the remaining specification items fixed, a specific range of TDERs could be more easily defined around the five items indicated above.

The Scottish Government proposes to replace the presentation of notional buildings within the Technical Handbooks with a set of target range tables. These tables will present a range in which the actual given building delivered energy value should sit. It will be through the use of the approved methodologies that the building specification single target and actual figures will be defined as is the case in the current method.

Given the remaining high number of activity and building types able to be defined for non-domestic buildings we will consider the responses to this consultation and undertake additional research into 2026 and 2027 to understand how such a target table range could be presented in a useful manner for building designers. For illustration, it is proposed that the Technical Handbooks will include a similar table to that shown in Table 8. The target ranges would be determined by the level of challenge indicated in section 6.1 of this consultation.

Table 8: Illustration of target range table to be presented in updated non-domestic technical handbooks

Heat solution	Heat pump TDER (kWh/m2/yr)	Heat network TDER (kWh/m2/yr)	All other solutions TDER (kWh/m2/yr)	Heat pump TSHR (kWh/m2/yr)	Heat network TSHR (kWh/m2/yr)	All Other Solutions TSHR (kWh/m2/yr)
Archetype
Retail and Financial/ Professional services	X-X	X-X	X-X	X-X	X-X	X-X
Restaurant and Cafes/ Drinking Establishments and Hot Food Takeaways	X-X	X-X	X-X	X-X	X-X	X-X
Offices and Workshop businesses	X-X	X-X	X-X	X-X	X-X	X-X
General Industrial and Special Industrial Groups	X-X	X-X	X-X	X-X	X-X	X-X
Storage or Distribution	X-X	X-X	X-X	X-X	X-X	X-X
……	X-X	X-X	X-X	X-X	X-X	X-X

To add further clarity using two examples:

• For ‘Office and Workshop businesses’ that have a heat pump as its heat source the TDER for that particular building will sit within a range dependent on the level of challenge that is chosen and defined by the fluctuation in TDER dependent on where the actual building is located, the mix of activity types, and the orientation in which it is fixed.
• For ‘Office and Workshop businesses’ the target space heating rate for that building will sit within a range dependent on the level of challenge chosen and where the actual building is located, the mix of activity types and the orientation in which it is fixed. Note that the target space heating rate should not be affected by the choice in heat solution in the actual building.

Consultation Question 19

Do you agree with the proposal to present the target rates for new non-domestic buildings within a target range table, replacing the notional building specification currently shown in Table 6.1 in the Technical Handbooks?

Yes

No

Please provide a summary of the reason(s) for your view.

6.3 Fabric performance for new non-domestic buildings

The guidance to standard 6.2 ‘Building insulation envelope’ sets out robust maximum recommended thermal (‘backstop’) values for elements of the building insulation envelope. This defines the general level of expectation in limiting heat loss. That level is set, alongside the requirements of standard 6.1, to enable a degree of flexibility in the delivery of cost-effective levels of fabric performance that are viable for projects across Scotland.

The guidance also emphasises the importance of addressing air infiltration in new buildings to reduce heat loss and energy demand. Whilst it remains difficult to achieve a specified air infiltration rate to any degree of accuracy, the February 2023 energy standards introduced the requirement for air pressure tests to be performed on most new buildings as set out in CIBSE TM23: ‘Testing buildings for air leakage’, to verify that the infiltration rate declared at the design stage is achieved on completion.

The Passivhaus system sets a single total energy use and a single space heating demand target without being explicit on the fabric U-values that must be met. Additionally, one of the key principles of Passivhaus is to achieve a particular airtightness level set at equal or less than 0.6 ACH @ 50 Pa.

6.3.1. Proposals

Given the extent of change within building standards with the implementation of the February 2023 standards and the effect other measures within Section 6 and proposals within this consultation have on the need to improve fabric U-values we propose to retain the maximum U-values as indicated in table 6.3 of the current non-domestic building standards technical handbook and as copied in table 9 below. This position reflects the reporting on the cost/benefit of further improvements to fabric performance within the Non-Domestic Research Paper and also the need to maintain a reasonable degree of flexibility between the consultation proposal for the non-domestic level of challenge set in section 6.2 of this consultation and the maximum performance of individual elements.

Table 9: Proposed maximum area weighted U-values for fabric elements for new non-domestic buildings

Type of element	Area weighted average U-value (W/m2K) for all elements of the same type
Wall	0.21
Floor	0.18
Roof	0.16
Windows and roof windows	1.6
Rooflights	2.2
Pedestrian doors	1.4

Given the theme of this review, responses to the stage one consultation and the Non-Domestic Research Paper we propose to set a provision in guidance for an ‘upper limit’ for fabric infiltration. For any new building that has declared a design infiltration of 5 or poorer, we propose that a design statement should be provided alongside the application for building warrant. This should set out the approach taken in the fabric specification and the specific considerations that have led to less of an emphasis on limiting fabric infiltration. We would anticipate that this would be integrated with the reporting on compliance for energy and environmental standards indicated in section 9 of this consultation.

Consultation Question 20

Do you agree with the proposal to set a provision in guidance for an ‘upper limit’ to the declared design air infiltration rate?

Yes

No

Please provide a summary of the reason(s) for your view.

6.4 Standard 6.1 approved compliance methodologies for new non-domestic buildings

Standard 6.1 ‘Energy demand’ requires that “the energy performance is calculated in accordance with a methodology of calculation approved under regulation 7(a) of the Energy Performance of Buildings (Scotland) Regulations 2008”. The current approved methodology for non-domestic buildings is identified in guidance published in support of standard 6.1: Simplified Building Energy Model (SBEM) version 6 of the methodology is to be used for compliance with the current standards.

The Scottish Government has procured the development of an updated compliance tool for non-domestic buildings based on the UK Government’s version 7.

The key outcome sought from a calculation methodology should be that it is robust and representative of the performance of the building, presenting an accurate illustration of the effect that any combination of building elements will deliver. That representation should approximate the outcome expected in the real world.

Through 2025 the Scottish Government procured research to review the outputs of building energy models against several standardised building specifications. This research is published here:

The building energy models reviewed were:

• Simplified Building Energy Model v 6.1
• Passivhaus Planning Package (PHPP) version 10.6.

Table 10 indicates a summary of the delivered energy outputs from the building energy models across seven building archetypes. The specification applied across the archetypes are defined as the Business as Usual models which represent what is currently being developed in Scotland.

Table 10: Summary of delivered energy outputs from a selection of methodologies

Delivered Energy (kWh/m2/yr)	SBEM v6.1	PHPP v10.6
Deep plan office (air conditioning and heat pump)	28.50	32.76
Health centre (district heating and mechanical ventilation)	12.86	15.14
Hotel (natural ventilation and direct electric)	265.27	228.16
Secondary school (air-conditioning and district heating)	32.50	13.01
Retail (mechanical ventilation and heat pump)	27.52	26.35
Shallow-plan office (air conditioning and district heating)	18.21	32.76
Distribution warehouse (mechanical ventilation and direct electric)	38.58	20.31

The Non-Domestic Research has found that SBEM and PHPP agree on the direction and magnitude of changes to energy consumption arising from changes in specification. However, there is a wide range in the difference in output between SBEM v6.1 and PHPP v10.6 across the indicated building types. The results also indicate that the building physics of the PHPP model does align with SBEM and these predict a similar level of impact for individual and grouped specification changes. However, there are some areas of building energy consumption such as heating, cooling and auxiliary systems that are significantly different to SBEM. Even though the two building models may disagree on the total energy consumption of a building there are suggestions that they may agree on the percentage improvement that differences to the target setting specification would yield.

Development of Scottish consultation compliance tool

Building on the 2025 research the Scottish Government procured the development of a Scottish version of the UK Government’s SBEM v7.

The Scottish Government version 7 applies updates to the UKG version to capture changes that were implemented within the February 2023 standards that differed from approaches applied in the rest of the UK, including:

• The benefit of electricity generated onsite that is applied within the standard 6.1 compliance calculation will only be that proportion that is used onsite
• Focus on Delivered Energy as the main compliance metric with changes to the methodology for buildings connected to heat networks

The development work also applies aspects that are proposed elsewhere within this stage two consultation, however, this work is still live and the version of the tool at the link below does not capture all proposed changes. The current consultation version of the Scottish SBEM v7 tool has been tested for usability prior to launch.

Consultation Question 21

Do you have any views on the development and usability of the consultation version of the Scottish SBEM v7?

Yes

No

Please provide a summary of the reason(s) for your view.

Future development of the Scottish compliance tool

A final version of the Scottish non-domestic compliance tool will build on the consultation version and will apply confirmed actions once the responses to this consultation have been analysed.

Consideration of additional compliance methodologies

The Passivhaus standard is supported by PHPP as a design and calculation tool with the tool being used within certified Passivhaus projects from inception. PHPP is based on the same building physics principles as SBEM and with slight modifications to the reporting could produce the equivalent proposed metrics.

6.4.1. Proposals

As part of confirming the Scottish equivalent to the Passivhaus standard we propose to recognise a modified version of PHPP as an approved methodology indicated in guidance to Standard 6.1 ‘Energy demand’ for new non-domestic buildings. We will work with the Passivhaus Trust and Passive House Institute to modify the existing PHPP tool to align it with the requirements of a Building Regulations compliance tool and capture the intent of additional changes as part of this review as indicated in proposals to other questions. This work will also compare outputs from PHPP and the proposed Scottish version of SBEM v7 to capture potential updates to both methodologies, so outputs are aligned where possible.

The final modified PHPP regulatory compliance tool will be presented for testing once complete.

Consultation Question 22

Do you agree with the proposal to recognise a modified version of PHPP as an additional tool that implements the approved methodology for standard 6.1 ‘Energy demand’ for new non-domestic buildings?

Yes

No

Please provide a summary of the reason(s) for your view.