Building standards technical handbook 2022: non-domestic

Guidance on achieving the standards set in the Building (Scotland) Regulations 2004. This handbook applies to a building warrant submitted on or after 1 June 2022 and to building work which does not require a warrant commenced from that date.

Annex 6.D Improvement to the energy performance of existing building services when carrying out building work

6.D.0 Introduction

Scottish Ministers have powers under section 25 of the Building (Scotland) Act 2003 to make a Direction to local authorities where they consider that buildings of any description to which building regulations apply ought to comply with a provision of the regulations.

This power is now exercised to direct local authorities to secure improvement to the energy performance of existing non-domestic buildings. The Direction to local authorities, which enable the following measures, is published on the Building Standards Division website.

6.D.1 Application of Direction

Made under section 25 of the Act, the effect of ‘The Building (Scotland) Act 2003 Improvement to the Performance of Fixed Building Services for Existing Non-Domestic Buildings Direction 2010’ is to introduce a requirement to make proportionate and cost-effective improvements to the energy performance of existing fixed building services when proposing new work to an existing non-domestic building.

For the Direction to apply, the following three conditions must be met. The proposed new work (alteration or extension) must:

  1. be of a scope that would require an application for building warrant (to enable verification of proposals), and

  2. have an estimated value of works, excluding improvement works, of £50,000 or more (to avoid a disproportionate administrative burden on smaller works), and

  3. include work to provide completely new fixed building services or to alter or extend the capacity of existing fixed building services to which Standards 6.3, 6.4, 6.5 or 6.6 apply (to enable improvement without the need to engage additional contracting expertise).

If any of the above are not applicable, improvement of existing building services is not required to demonstrate compliance with Standards 6.3 to 6.6.

Where these three conditions are met, there are also specific exceptions to the need to carry out improvement work. These are:

  • the Direction is not applied to proposed works which are primarily to improve the carbon or energy performance of an existing building (as the intent of the Direction is already met by such work), or

  • existing fixed building services which already meet specific provisions within building regulations applicable since 4 March 2002 need not be improved further (see clause 6.D.7 for further information). This exclusion does not apply to replacement of boilers or existing air-conditioning chiller units as improvement is based on the age of the current installation, not a specified performance standard.

Reference can be made to the application checklist (Table 1) below, which outlines the key questions in the assessment and verification of this process.

6.D.2 Scope of improvements (types of installations which should be assessed)

Applicants should assess the potential for cost-effective improvement in the following areas, each of which is addressed in guidance on compliance to Standards 6.3, 6.4, 6.5 or 6.6 within the 2015 Non-domestic Technical Handbook:

  1. upgrading of heating controls and system components (Standard 6.3)

  2. upgrading of insulation to hot water storage vessels (Standard 6.4)

  3. upgrading of lighting controls and luminaires (Standard 6.5)

  4. upgrading of ventilation or cooling controls or system components (Standard 6.6)

  5. replacement of existing boiler, if more than 15 years old (Standard 6.3)

  6. replacement of existing air-conditioning chiller units, if more than 10 years old (Standard 6.6).

Assessment need only consider the types of fixed building services within the existing building that also form part of proposed works (for example, if no water services or plumbing element under proposed works, there is no need to consider improvement to insulation of vessels and work to circulatory elements to wet heating systems). The intent of this is to avoid the need to engage specialist contractors that are not already involved in a project. However, the applicant may broaden the scope of improvements considered if they choose to (for example, where the applicant considers such improvements to be more relevant to the building in question).

6.D.3 Extent of improvement required (assessing cost and practicality)

Improvement should be proportionate to the extent of proposed works. It is recommended that the cost of improvement works should amount to approximately 5% of the cost of proposed work. In this respect, assessment should be based upon cost of carrying out improvement works, exclude any design or consultancy fees. Where proposed improvements amount to less than this percentage, the applicant should, in scheduling the assessment process, provide evidence to support any reduced level of improvement.

It is the intent that improvement works proposed should be cost-effective, with a short to medium payback period. Assessment need only consider improvements that, when combined, have a payback period of five years or less. The exception to this is the replacement of a boiler or chiller unit, where near the end of its useful life, as there will be additional cost benefit where replacing such equipment as part of more extensive works.

The cost of any improvement works should be included in the estimated value of works used to determine the level of building warrant fee. The value of improvement works and proposed works should be identified separately to allow the proportion of improvement works to be verified.

Work to improve fixed building services should be neither overly disruptive to the operation of the existing building nor require costly or extensive intervention to the building fabric. However, it is recognised that work chosen by the applicant (see clause 6.D.4) may be of such a nature. Where such enabling work is required, it should not be counted as part of the cost of improvement work.

6.D.4 Assessment by applicant

To deliver improvements that are both cost-effective and relevant to the building being assessed, the types of improvement taken forward should be determined by the person responsible for the building (the relevant person/applicant) in consultation with any appointed agent or consultant. Recognising the complexity of the existing building and its systems, assessment should be carried out by persons with the necessary expertise to identify and assess cost-effective and energy efficient improvement.

The intent of the Direction is to deliver cost-effective improvement to the performance of the existing building services. Applicants should be aware that it is therefore in their best interests for existing fixed building services to be examined and assessed, to enable the most effective and beneficial improvements to be identified for consideration.

As noted in clause 6.D.2, whilst specific fixed building service issues are identified, the applicant may propose alternative improvements where they consider these more relevant to the building and can demonstrate that such improvement will deliver broadly equivalent benefit.

Where an Energy Performance Certificate or similar assessment exists for the building, it would be good practice to check any recommendations on existing fixed building services amongst the cost-effective improvements already identified.

For buildings with air conditioning systems, applicants should be aware of the need for inspection of systems over 12kW under regulation 17 of the Building (Scotland) Regulations 2004 and, where applicable, should consider instructing such an inspection where such systems are present. Information from this report will assist in assessing potential improvement to such systems under this Direction.

To maximize benefit to the building, improvements should meet current performance levels recommended in the guidance to Standards 6.3, 6.4, 6.5 and 6.6 where this is reasonably practicable. Where not reasonably practicable, for technical reasons or for reasons of cost or level of disruption to the building, improvement should still be made to the extent that can be achieved. The applicant should take advice on the impact which a lower level of improvement may have on the cost effectiveness of such work and may choose to not make such improvements where payback periods are longer than five years. The case for this should be presented to the verifier.

6.D.5 Review by verifier

The primary role of the verifier is to check that the process outlined above is observed and that proposed improvements to existing building services are of a scale appropriate to the proposed works or, if not, that substantiation for a reduced level of improvement is provided and is justifiable.

Whilst the verifier may question the extent of proposals and request further evidence to support such enquiries, it is not expected that they should direct the types of improvement which are to be carried out for a particular case.

On acceptance of proposals by the verifier, works arising under this Direction are subject to the same process as all other works requiring a building warrant, where the responsibility of the relevant person/applicant is to carry out works in accordance with the issued building warrant and the requirements of the building regulations in general. The verifier will make reasonable enquiry to establish this, prior to accepting a completion certificate.

6.D.6 The role of the Local Authority

Due to the checking integral to the building warrant process, the local authority should generally have no direct role in this process other than as verifier. However, under section 25 of the Act, the local authority may serve a building regulations compliance notice on the building owner, if the improvement work is not carried out. Where the building owner fails to comply with the notice they are guilty of an offence.

However, it should be noted that, if none of the proposed building warrant work is carried out on the building, no improvement work to existing fixed building services need be carried either.

6.D.7 Supplementary information - Exclusion by compliance with previous standards

The performance of components in installations less than 13 years old (post 4 March 2002) need not be improved further where the minimum performance meets levels set within building regulations. The intent of this limitation is to avoid replacement of elements where installations are both recent and relatively energy efficient as this will generally be less cost-effective.

Applicants should note that, as a wider range of building services issues are now addressed within building regulations (an example in 2010 being the introduction of a minimum efficiency for circulators and pumps), it will be necessary to measure performance of some elements against the current edition of the standards, where a level of performance is not identified in previous editions of the building regulations.

Table 6.13 Process checklist

Figure 6.3. Table 6.13 Process checklist

Table 6.13 Process checklist

6.D.8 Examples of the process

Example 1

A primary school building, completed in 2000 is being extended to acquire a new staff room. The estimated value of the new work is £50,000. Proposed works include power, lighting, heating and ventilations systems. The capacity of the existing boilers is sufficient to cater for the heating and hot water requirements of the extension. The building already has an EPC which offers recommendations for cost-effective improvement.

After further assessment of the fixed building services in the existing school, the following improvement measures are identified:

  • Installation of variable speed drives (VSDs) to the heating system at a cost of £1,800, with annual fuel cost savings of £244 giving a payback period of 7 years.

  • Installation of T5 retrofit kits to general lighting at a cost of £700, with annual fuel cost savings of £200 giving a payback period of 3.5 years.

  • Installation of lighting daylight sensors at a cost of £2,400, with annual fuel cost savings of £777 giving a payback period of 3 years.

The third option (installation of the daylight sensors) has a short payback period and a higher annual fuel cost saving which may make it the preferred option in isolation, if there were no preference for the type of improvement to be carried out in the existing building.

The combined cost of the two first options is £2,500, with a total annual fuel saving of £488 and a (combined) 5.6 year payback and therefore could qualify if the slightly long payback period is acceptable.

In this case, the building owner is advised that the saving from combining daylight sensors and T5 retrofit would be reduced (as sensors would act to improve a lighting load already reduced by the T5 retrofit) and, having experienced increased heating bills over recent years, elects to improve the performance of the heating system instead of installing sensors. On that basis, the first two improvement options, which constitute around 5% of the proposed value of works, are scheduled as part of the submission to the verifier.

Example 2

A primary health care building, completed in 2001, is extended to provide a café at a cost of £55,000. The existing building services are to be extended to supply the new café. The building already has an EPC which offers recommendations for cost-effective improvement. The building contains an air conditioning system over 12kW and an inspection of the system and report was prepared previously. The report includes some minor recommendations that will improve performance.

Following on from further assessment of the fixed building services in the existing building, the following improvement measures are identified:

  • Installation of T5 retrofit kits to general lighting at a cost of £3,900, with annual fuel cost savings of £493 giving a payback period of 8 years

  • Replacing GLS with CFL lighting at a cost of £2,200, with annual fuel cost savings of £3,250 giving a payback period of less than 1 year

  • Installation of variable speed drives (VSDs) to the heating system at a cost of £2,300, with annual fuel cost savings of £59 giving a payback period of 40 years.

The first option (installation of T5 retrofit kits) is above the 5% cost and the payback period (in isolation) is long. The third option (installation of variable speed drives), while within the identified 5% cost margin, has an unrealistically long payback period which would not make it a suitable choice for improvement.

The remaining improvement item has a short payback period and amounts to less than 5% of the proposed value of works. The recommendations to improve the air conditioning systems are low cost but would contribute to assessment under the Direction.

The building owners choose to implement the second option (replacing GLS with CFL) which has a short payback period and a high annual fuel cost saving, even though the initial cost is below the identified 5% works cost. They also identify improvement to the air conditioning system and the small cost this incurs. As works remain below the identified 5% works cost, evidence is provided to show that no other cost-effective improvements are applicable to the building. Proposed work and evidence of further assessment carried out are scheduled as part of the submission to the verifier.

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