Building regulations - energy and environmental standards: consultation on proposed changes

2 Consultation proposals

2.1 Defining a Scottish equivalent to the Passivhaus standard

2.1.1. Background

As noted in section 1.1.2, Ministers have committed to give effect to Alex Rowley MSP’s Proposed Domestic Building Environmental Standards (Scotland) Bill, to “introduce new minimum environmental design standards for all new build housing to meet a Scottish equivalent to the Passivhaus standard, in order to improve energy efficiency and thermal performance”.

We intend to consult initially on a range of principles that would define how we set relevant standards in the future. These principles will reflect the current intent of our standards and discuss the provisions inherent in the approach taken by the Passivhaus standard. Elements of which can potentially be incorporated into the building standards system where deliverable at scale and beneficial in driving improved targets or to processes which assure the outcomes sought.

The outcome of this stage 1 consultation will inform both amendment to regulations later this year and the structure and content of a further consultation, on the detail of proposals, in summer 2025.

2.1.2. Current building standards on energy and environmental performance

The current building standards for energy and relevant environmental topics are set out within sections 3, 6 and 7 of the Building Standards Technical Handbooks. These can be summarised, briefly, as follows:

• Almost all new buildings are subject to an overall energy performance target under standard 6.1. This uses ‘delivered energy’ as its compliance metric and sets targets based upon comparison of the specification and performance of the actual building with that of a ‘notional building’ specification, defining a ‘relative’ performance target, one which varies with the built form proposed.
• The current UK calculation methodologies are used to demonstrate compliance. SAP for new dwellings and SBEM for new non-domestic buildings. Performance is calculated using a range of set parameters and the use of national climate data.
• Minimum elemental performance standards or expected provisions for building fabric and fixed building services are set out under standards 6.2 to 6.6, 6.10 and 6.11. The last of these, introduced in April 2024, moves new buildings away from fossil fuel and other polluting heating systems.
• Requirements for commissioning of installed systems and the provision of written information to building users are set out under standards 6.7 and 6.8
• The production of an energy rating (energy performance certificate) is sought on completion of almost all new buildings under standard 6.9.
• The requirement to provide a means of heating to dwellings is set under standard 3.13.
• Requirements for ventilation in buildings are set under standard 3.14.
• Provisions to limit peak summer overheating are set for dwellings and similar non-domestic residential buildings under standard 3.28.
• Standard 7.1 requires a statement of sustainability is provided for new buildings, which includes reporting on several energy-related topics.

2.1.3. The Passivhaus standard

The Passivhaus standard is a well-established voluntary standard. The standard is focused on delivering buildings with very low energy demand and high levels of occupant comfort through an informed approach to the optimisation of building form, orientation and design and effective quality assurance (QA) processes. There is increasing recognition and application of the standard, which contributes positively to overall energy and net zero objectives.

The standard sets absolute targets for space heating/cooling demand, total energy consumption (‘Primary Energy Renewable’) and fabric airtightness. There are also limits on minimum internal surface temperatures and periods of summer overheating.

Targets are commonly achieved by a combination of very high standards of fabric insulation, including high performance glazing and close to thermal bridge free design. Effective ventilation is provided by a mechanical system with efficient heat recovery. The standard can be considered relatively prescriptive in the solutions implemented, solutions which themselves are sensible actions which contribute to the performance and comfort outcomes the standard seeks.

Designers can choose to become formally certified in the principles of the standard and the application of its supporting design and modelling tool, the Passive House Planning Package (PHPP), used to demonstrate performance targets are achieved. The design and construction of Passivhaus buildings is subject to QA via a third-party certification process, overseen by a Passivhaus certifier.

Information on Passivhaus is available on the website of the Passivhaus Trust, the UK Passive House Organisation.

2.1.4. Commentary on application of the Passivhaus standard.

The Passivhaus standard seeks to deliver buildings with very low energy demand and a good internal environment through a combination of good design, optimisation of form and orientation, an informed approach to specification of building elements and outcomes and a robust QA and certification regime. This is supported by a calculation tool which is engineered to present outcomes in a manner that relate closely to likely real world use.

Prescriptive targets are included, including absolute values set for particular metrics such as space heating demand and energy use intensity. The need for the design of buildings to consider form and orientation to optimise performance is strongly emphasised by the use of absolute performance targets, particularly for space heating.

Several sub-outcomes are delivered by a particular approach to specification of elements including use of high efficiency mechanical ventilation and heat recovery (MVHR), maximum infiltration levels for building envelope and minimum surface temperature of elements to improve thermal comfort. Plus the expectation that those involved in the design and construction process are appropriately trained in the delivery of very low energy buildings and can report progress in a manner that demonstrates effectiveness of process to the registered Passivhaus certifier who provides oversight. This includes a detailed approach to recording of evidence of good practice in design, specification, construction and commissioning.

In summary, Passivhaus seeks very high and assured levels of energy efficiency and a healthy and comfortable indoor environment all year round. It encourages a design-led approach to optimise built form to limit energy demand and meet the standard. It requires:

• Calculation and reporting of outcomes through the use of PHPP.
• Space heating demand of not more than 15 kWh/m²/yr or a heating load of not more than 10 W/m². And a similar limit on cooling demand, where present.
• Envelope airtightness of not more than 0.6 air changes per hour.
• Primary Energy Renewable demand (all energy use, including the storage and distribution losses of the building) of not more than 60 kWh/m²/yr (this includes appliances). The limit value applies for typical residential, educational and office/administrative buildings.

Passivhaus also sets general minimum criteria:

• Designing out additional heat loss at junctions
• Not more than 10% of year with indoor temperatures above 25 ºC.
• Not more that 20% of year with humidity above a specified limit (12 g/kg).
• The whole building ventilation rate shall be at least 20 m³/h/person (maximum design occupancy) and 0.3 air changes per hour. Minimum system heat recovery efficiency must exceed 75%. Winter humidity levels are estimated during design and low humidity avoided through strategies such as demand controlled ventilation.
• Limits on noise from ventilation system - 25/30 dB(A).
• Limits on minimum temperature of internal surfaces (not less than 17 ºC).

There is therefore a significant amount of good practice which can be drawn from the established Passivhaus approach and applied within the Scottish building standards system.

In the context of this first stage consultation, we are seeking to understand the extent to which the components of the Passivhaus approach are desirable and deliverable at a national level within regulations and where such provisions would need to be embedded in legislation rather than in supporting guidance.

2.2 Identifying the components of an equivalent standard

2.2.1. Context – application as national minimum standards.

This statement, to deliver ‘a Scottish equivalent to the Passivhaus standard’ continues to create an expectation around both the anticipated outcome of the review and the approach to development of proposals. This is primarily because Passivhaus is such an established and well-known standard for the delivery of very low energy buildings. And it offers a very clear and specific approach and certain reportable outcomes.

A discussion on what can be considered as ‘equivalent’ needs, first and foremost, to recognise the difference in application of a voluntary standard and mandatory regulation. A standard such as Passivhaus has relative freedom in defining outcomes – targets and the manner in which they are to be achieved. It can be aspirational, stretching or best practice but achievable in practice for those who understand its implications and choose to apply it. Completed projects over many years have demonstrated this is the case for Passivhaus.

However, as a voluntary standard it does not have to demonstrate that it is both necessary and the best way of achieving a given outcome, taking into account economic and broader societal outcomes at a national level. Review of minimum standards set through regulations are subject to such controls. For this reason, ‘equivalent’ must mean that which can be interrogated, learned from and implemented within the context of national minimum standards to deliver similar goals.

Considering the context for this review – delivery of nationally applicable standards – it is useful to set out this statement to clarify what ‘equivalent’ means in the context of national standards. Dialogue on this issue, informed by 2023/4 engagement with key stakeholder organisations, has led to the following initial summary statements, which build on the two points in section 1.1.2.

2.2.2. Actions identified and considered by the review.

Ministers have committed “to introduce new minimum environmental design standards for all new build housing to meet a Scottish equivalent to the Passivhaus standard, in order to improve energy efficiency and thermal performance”.

To achieve this, the intent of this review is to deliver:

• Improvements to the setting of energy performance and ventilation standards for new buildings, leading to lower energy demand (and reduced running costs) and assurance of a healthy indoor environment.
• Improvements to the design and construction process to give greater assurance that compliance, and therefore the performance sought, is delivered in practice.
• A level of action, deliverable at a national level, which reflects the needs of building users and strategic policy objectives around climate change, energy policy and the built environment.

In this context, ‘equivalent’ should not necessarily mean that:

• We adopt and implement Passivhaus for all new development;
• Our standards must consistently achieve built outcomes at least as good as Passivhaus; or
• We set a standard which requires a similar level of prescription on key energy-relevant elements of building specification.

Consultation Question 1

Do you broadly agree with the statements on what ‘equivalent’ should not mean, in delivery of amended building standards to address energy and environmental performance?

Yes

No

Please provide information on why you agree or disagree or if you consider other actions need to be considered.

However, ‘equivalent’ should require the following:

• We remain aware that the standards we set have to be deliverable for all new buildings at a national level to an agreed timetable, post-2024.
• We base the capacity for change on an understanding of what solutions are currently being delivered to the February 2023 standards, to define a current baseline.
• We have interrogated the practical application of the Passivhaus standard and understand the outcomes it delivers and how these are achieved.
• There is an understanding of differences in outcome due to the application of our respective processes, including chosen calculation methodologies.
• We are able to illustrate how the outcomes of our standards currently compare with those of Passivhaus certified projects.
• We understand and will consider the application of elements which form the Passivhaus approach to target setting where this can be shown to be beneficial and deliverable at scale.
• The manner in which we define and set out targets should support considered and effective low energy design, where practicable.
• Action to increase assurance of outcome should cover both design and construction phases as a single process with emphasis on competence, effective communication, risk management and reporting on activity throughout that process.
• The compliance model we implement should be shown to apply a robust approach to assurance which is defined within a framework that is scalable to the extent of works and able to incorporate future enhancements, be these improved targets or additional assurance elements.
• Any confirmed approach should not result in barriers to use of specific solutions or to the voluntary application of higher standards than those set under our regulations.
• We should recognise valid alternative means of compliance where these are deliverable via our updated regime and where outcomes can be verified simply and effectively by other means.
• The standard we set must align with broader Ministerial Objectives for the built environment, including key strategies such as Heat in Buildings and Housing to 2040.

The above list sets out the rationale for the proposed approach to delivering change through the building standards system. Both in the defining and setting of performance targets and the means by which evidence of compliance is provided.

Consultation Question 2

Do you broadly agree with the statements on what ‘equivalent’ should require consideration of, in delivery of amended building standards to address energy and environmental performance?

Yes

No

Please provide information on why you agree or disagree or if you consider other actions need to be considered.

2.2.3. Outcomes sought by this review

Essential

• Identification of deliverable improvement on current energy standards to further reduce the delivered energy needed by new buildings. This includes the manner in which we define such targets.
• Improved assurance that compliance with standards and design intent is achieved in practice. This covers both energy and ventilation/comfort topics.
• A clear statement on what is being delivered and how ‘equivalence’ with the cited Passivhaus standard is achieved by change in standards and processes.

The last item above is informative and not subject to a requirement for assessment and reporting on the impact of regulatory change.

Initial action for December 2024

• Amendment of regulations to introduce prescription on the manner in which any required outcome is achieved or the manner in which compliance is to be demonstrated. Where such provisions are not included in regulation at present.

2.2.4. Outcomes already achievable under current legislation

In the context of the above and the intent to amend regulations to enable delivery of the proposed standard, it is useful to note that the following provisions are already delivered by the building standards system:

• Requirement for work to be carried out in a technically proper and workmanlike manner, and the materials used must be durable, and fit for their intended purpose.
• Requirement that any service, fitting or piece of equipment provided to serve a purpose under the regulations shall do so in a way that furthers that purpose.
• Setting of standards for overall building energy performance (regulated energy demand, reported as delivered energy, metric is not prescribed in regulation).
• Setting of minimum performance standards for building fabric and services (expected performance not prescribed in regulation).
• Setting of minimum standards for building ventilation and overheating risk (expected performance is not prescribed in regulation).
• Requirements for both commissioning of building systems and the provision of information on the operation and maintenance of installed services to the occupier (specific actions are not prescribed in regulation).
• Demonstration of compliance (overall building energy performance) via a methodology approved by Ministers (standard refers to methodology approved under other legislation, methodology itself is not prescribed in regulation).
• Prescription on information which must be provided in support of a building warrant.
• Prescription on information which must be provided in support of a completion certificate.

2.2.5. Developing proposals for amendment of regulations

The current delivery of energy and related standards is primarily through a combination of mandatory functional standards (statements of the outcome which must be achieved) set out under regulation 9 ‘building standards applicable to construction’ and supporting guidance (to illustrate how that outcome would generally be achieved and the component actions which need considered).

Initial investigation into the extent of regulatory change needed to support a proposed standard and the outcomes noted in paragraph 2.2.2 has concluded that changes to regulations will most likely be needed where a particular outcome or process requires to be reinforced where explicit statements in guidance, which are phrased as ‘should’ rather than ‘must’, do not provide sufficient direction on the action needed.

A provisional summary of candidate changes to regulations, drawn from internal review of current provisions, is set out in Annex A.

It should be borne in mind that prescription on the face of a standard or regulation can significantly limit the range of solutions available to an applicant or developer and may curtail approaches which can achieve the same outcome effectively by another route.

If the outcome sought cannot reasonably be delivered in all cases, this may also lead to applications to Scottish Ministers to formally relax or dispense with the provision. Such issues must be considered when determining where direction is placed on a given issue within regulations, standards and guidance.

Proposals on a range of relevant topics are set out in the next section. For most topics, commentary is provided on whether it may be a candidate for regulatory change, any proposed position on changes and the reason for proposals.

Your view is sought on each topic and any related matters you consider relevant to the outcome of this review. This will inform the necessary amendment of regulations in December 2024 and the development of our second consultation in summer 2025.