Publication - Advice and guidance

Building Standards technical handbook 2017: non-domestic buildings

The Building Standards technical handbooks provide guidance on achieving the standards set in the Building (Scotland) Regulations 2004 and are available in two volumes, Domestic buildings and Non-domestic buildings. This publication is available in html and also in PDF format (in 'supporting documents' ).

Building Standards technical handbook 2017: non-domestic buildings
6. Energy

6.0 Introduction

6.0.1 Background

Within Scottish building regulations, improvements in energy standards have been made over many years, including in 2007, the move to a single carbon dioxide emission based methodology for assessing carbon and energy performance in new buildings.

The Sullivan Report - in 2007, Scottish Ministers convened an expert panel to advise on the development of a low carbon building standards strategy to increase energy efficiency and reduce carbon emissions. This resulted in The Sullivan Report – ‘A Low Carbon Building Standards Strategy for Scotland’ (http://www.scotland.gov.uk/Sullivanreport). A key recommendation of this Report was staged improvements in energy standards in 2010 and 2013, with the aim of net zero carbon buildings (emissions for space heating, hot water, lighting and ventilation) in 2016/17, if practical.

In May 2013 Scottish Ministers reconvened the Sullivan panel with a view to revisiting some of their original recommendations, taking account of the impact of the economic downturn on the construction sector. Whilst maintaining the level of ambition, the 2013 Update report recommended a more moderate pace of change and offered recommendations in three areas:

  • eventual and staged standards – Percentage improvements recommended in 2007

  • process – Extending carbon compliance beyond site - related measures and

  • costings – Recognising the value of new - build energy standards.

The Climate Change (Scotland) Act 2009 (http://www.legislation.gov.uk/asp/2009/12/pdfs/asp_20090012_en.pdf) creates a statutory framework for delivery of greenhouse gas emissions reductions in Scotland. The Act sets an interim target of a 42% reduction in emissions (compared to 1990) by 2020, and an 80% reduction target for 2050 with annual targets set in secondary legislation. The high level measures required in each sector to meet Scotland’s statutory climate change targets, for 2022 and in the long term, were set out in the Scottish Government’s Climate Change Delivery Plan. This includes recommendations for the delivery of low carbon new buildings.

The construction sector has a major role to play in this respect. Emissions from the burning of fossil fuels are contributing to climate change, with energy use in buildings being a significant source of such emissions. Increased energy efficiency and promotion of renewable energy are therefore an important element of Scotland’s strategy to tackle climate change.

To deliver buildings that are more energy efficient and have fewer carbon dioxide emissions, a greater emphasis is needed on the overall effect that design and specification choices, construction and commissioning of new work can have on building performance.

6.0.2 Aims

The intention of Section 6 is to ensure that effective measures for the conservation of fuel and power are incorporated in buildings. In addition to limiting energy demand by addressing the performance of the building fabric and fixed building services, a carbon dioxide emissions standard obliges designers of new buildings to consider building design in a holistic way.

Improvements set out within this section will result in a greater need to consider the benefits which localised or building-integrated low carbon equipment (LCE) (e.g. photovoltaics, solar water heating, combined heat and power and heat pumps) can make towards meeting standards. Although the focus is primarily on lowering carbon dioxide emissions from buildings, the measures within this section are intended to reduce energy demand and continue to ensure that, for new buildings and new building work, use of energy and fuel costs arising from this are both minimised.

Guidance also recognises issues relevant to requirements within Articles 3, 4, 6-9 and 11 of the EU Directive 2010/31/EU on the Energy Performance of Buildings (EPBD) and Article 13 of the EU Directive 2009/28/EC http://europa.eu/legislation_summaries/energy/renewable_energy/en0009_en.htm on the promotion of the use of energy from renewable sources.

The standards and guidance given in this section are intended to achieve an improvement, for new buildings reducing emissions by approximately 43% compared to the previous 2010 standards (60% compared to the 2007 Standards). However nothing here prevents a non-domestic building from being designed and constructed to be even more energy efficient or make greater use of low carbon equipment (LCE).

6.0.3 General guidance

This section covers the energy efficiency for non-domestic buildings. Such buildings include: factories, offices, shops, warehousing, hotels, hospitals, hostels and also buildings used for assembly and entertainment.

This section should be read in conjunction with all the guidance to the Building (Scotland) Regulations 2004, but in particular Section 3 Environment, which has a close affiliation with energy efficiency, regarding:

  • ventilation

  • condensation

  • combustion appliances, and

  • biomass fuel storage.

When determining how to follow the Section 6 guidance for energy efficiency in buildings, recognition should be given to the following:

  1. an insulation envelope is only appropriate to those parts of a building that are intended to be heated or cooled. N.B. Heating rated at a maximum of 25W/m2 of floor area and installed only for the purposes of frost protection should be disregarded for the purposes of this guidance

  2. some concessions are given in annex 6C to modular and portable buildings (some of which could be stand-alone buildings). The flowchart in the annex gives guidance on possible compliance routes. Note there are no concessions for limited life buildings which are constructed in a conventional manner

  3. stand-alone buildings that are heated (see paragraphs below), and

  4. work on existing buildings (see paragraph below).

Heated stand-alone buildings - in 2007, the EU Directive 2002/91/EC on the energy performance of buildings introduced the category ‘stand-alone building’, a definition of which is given and within appendix A of the Technical Handbooks. The Directive, now recast as Directive 2010/31/EU, exempts such buildings, where less than 50m2 in floor area, from both the need to use a methodology to calculate energy performance (Standard 6.1) and also the production of an Energy Performance Certificate (Standard 6.9). The defined term includes not only detached buildings, but also thermally divided parts of a building with separate heating shut-down control.

Stand-alone buildings that are less than 50m2 in floor area, must still comply with Standards 6.2 to 6.8 and 6.10. The guidance to Standard 6.2 recommends that the insulation envelope of heated stand-alone buildings meets the level of performance applicable to an extension.

Examples - common examples of stand-alone buildings that could be less than 50m2 and which would therefore be eligible for exemption are: a detached petrol filling station kiosk, associated with a supermarket; and heated office and toilet accommodation, within an otherwise unheated warehouse.

Work on existing buildings - as for other standards within Scottish building regulations, the energy standards apply to conversions and also work on existing buildings, such as extensions, alterations and fit-outs. However in some situations, individual standards may not apply or guidance on compliance with the standards may differ for such work. The latter is usually to recognise constraints that arise when working with existing buildings.

It is advisable in the first instance to check the functional standard as sometimes a limitation removes certain classes of this type of work. Where not excepted by a limitation to the standard, the provisions of the standard will apply in full to the new work on the existing building, the exception to this could be where the standards are brought into effect by conversion and this is identified in the introduction to the guidance supporting each standard.

6.0.4 U-values

Thermal transmittance (U-value) is a measure of how much heat will pass through one square metre of a structure when the temperature on either side differs by one degree Celsius. It is expressed in units of watts per square metre per degree of temperature difference (W/m2K).

Measurements of U-values should be made in accordance with BS EN ISO:8990:1996 ‘Thermal insulation. Determination of steady-state thermal transmission properties. Calibrated and guarded hot box’. In calculation thermal bridging may be disregarded where the difference in thermal resistance between bridging and bridged material is less than 0.1m2K/W. For example, normal mortar joints need not be taken into account in calculations for brickwork, but should be taken into account for lightweight insulating blockwork.

Taking into account guidance from BRE publication BR 443:2006 ‘Conventions for U-value calculations’ (http://www.bre.co.uk/filelibrary/pdf/rpts/br_443_(2006_edition).pdf), individual U-values of building elements forming the insulation envelope should be established:

  1. by using insulation to a thickness derived from manufacturers’ data relating to thermal conductivities (W/mK) and thermal transmittances (U-values: W/m2K) certified by a notified body

  2. by calculation taking into account thermal bridging effects of, e.g. timber joists, structural and other framing and normal bedding mortar, by using the Combined Method set out in BS EN ISO 6946:2007 or CIBSE Guide Section A3, 2006 Edition (http://www.cibse.org/)

  3. for floors adjacent to the ground and basements, by using the method set out in BS EN ISO 13370: 2007 or CIBSE Guide Section A3, 2006 Edition

  4. for windows, doors and rooflights, by using BS EN ISO 10077-1: 2006 or BS EN ISO 10077-2: 2012 and, for rooflights, BS EN ISO 12567-2: 2005, or

  5. for metal cladding systems using Finite Element Analysis, the method of calculation should be made in accordance with BS ISO 10211:2007.

6.0.5 Thermal conductivity

The thermal conductivity λ (the λ-value) of a material is a measure of the rate at which that material transmits heat and is expressed in units of watts per metre per degree of temperature difference (W/mK). Establishing the thermal conductivity of materials in a building element forming part of the insulation envelope will enable the thermal transmittance of the element to be calculated.

Measurements of thermal conductivity should be made in accordance with BS EN 12664: 2001, BS EN 12667: 2001 or BS EN 12939: 2001 (http://www.bsigroup.com/). There are a wide range of technical publications which give the thermal conductivity of common construction materials but, where available, preference should be given to values that are certified by a notified body. Additional guidance given in BRE publication BR 443 should also be followed.

6.0.6 Thermal transmittance through separating elements

Previously, thermal transmittance through separating walls or separating floors between heated parts of the same building (e.g. between an office and a protected zone with space heating) was not assessed. Accommodation on both sides of the separating element was expected to be at a similar temperature when the buildings are occupied.

This is no longer always the case. Whilst ‘no loss’ may still be assumed for solid walls, research has identified previously unanticipated heat losses from air movement in cavity separating walls. This ‘thermal bypass’ is now identified in the calculation methodology and guidance to Standard 6.1 and in guidance to Standard 6.2.

6.0.7 Buffering effects on the insulation envelope

If a building or part of a building is separated from an unheated enclosed area, (e.g. solid waste storage accommodation, a porch, garage, protected zone or underground car park) the U-values of the walls/floors (including doors and translucent glazing) may be calculated by:

  1. disregarding the buffering effects and treating the element as if it is directly exposed to the outside

  2. following the procedure in BS EN ISO 6946: 2007, or

  3. following the procedure in BS EN ISO 13789: 2007.

6.0.8 Roofs that perform the function of a floor

A roof of a building that also performs the function of a floor or similar load-bearing surface (e.g. an access deck, escape route, roof garden or car park), should be considered as a roof for the purpose of assessment within this section.

6.0.9 Atria

In a building with an atrium the guidance given in clause 6.0.7 applies if the atrium is unheated and thermally divided from the remainder of the building by translucent glazing and doors and, if appropriate, walls and floors. In other situations involving atria, where none of the above occurs, the continuity of the insulation envelope occurs at roof level (usually predominantly glazed with translucent material) and the atrium is considered to be a heated part of the main building.

6.0.10 Annexes to guidance

Annexes can be found at the back of this section. These give guidance in respect of various calculation procedures, modular and portable buildings and consequential improvement to fixed building services.

6.0.11 Performance of fixed building services

Unless otherwise identified in text, guidance given in support of Standards 6.3 to 6.6 now refers directly to information contained within the Non-domestic Building Services Compliance Guide for Scotland . The document replicates guidance published in support of building standards elsewhere in the UK and supports standardisation of the specification and expected performance of fixed building services throughout the UK.

Additional information, on the use of a range of low carbon equipment (LCE) such as solar thermal systems, photovoltaic panels and heat pumps, and application within building regulations can be found on the Technical Pages of the Building Standards Division website.

6.0.12 Calculation of areas

When calculating areas for the purposes of this section and in addition to regulation 7, schedule 4, the following should be observed:

  1. all areas should be measured in square metres (m2), unless stated otherwise in this guidance

  2. the area of a floor, wall or roof is to be measured between finished internal faces of the insulation envelope, including any projecting bays and in the case of a roof, in the plane of the insulation

  3. floor areas are to include stairwells within the insulation envelope and also non-useable space (for example service ducts)

  4. the area of an opening (e.g. window or door) should be measured internally from ingo to ingo and from head to sill or threshold.

6.0.13 Latest changes

The 2015 edition of Section 6 incorporates a number of changes whilst retaining the existing methodology introduced in 2007. The majority of these changes relate to improvement in specified performance to deliver the intended 43% aggregate reduction in carbon dioxide emissions on the 2010 standards (60% when compared to 2007 standards). Foremost, in guidance to Standard 6.1 is the move to use of a concurrent notional building specification to set the Target Emissions Rate for new buildings. A full summary of changes can be found on the Technical Handbooks page of the Building Standards Division section of the Scottish Government website.

The key changes that have been made to standards and guidance since 1 October 2013 include:

  • Standard 6.1 - standard amended to apply to large extensions (over 100m² and more than 25% of the area of the existing building)

  • Standard 6.1 – SBEM v5 now used to calculate carbon dioxide emissions; both changes to methodology and revised carbon factors for fuels apply

  • Standard 6.1 – target Emissions Rate for new building now set using a concurrent (2015) notional building specification. Guidance comprehensively amended in support of this new approach (Revised NCM Modelling Guide for Scotland also published)

  • Clause 6.2.5 – revisions to calculation options for heat loss from linear thermal bridging

  • Clause 6.2.7 – revised list of situations where airtightness testing need not be undertaken

  • Standard 6.9 - standard amended to cover display of EPC in public buildings over 250m2 (note: applies from 9 July 2015)

  • Standards 6.3 to 6.6 - reference is now made to the Non-domestic Building Services Compliance Guide for Scotland for detailed guidance in support of each standard; any situations not addressed in this document are noted within the guidance to the relevant standard

  • Annex 6C – guidance for new modular and portable buildings update to reflect revised emissions targets; exemption for relocation of buildings under 30m² now expired

  • Annex 6G now published as Annex 6D; incorporating more comprehensive guidance on consequential improvement of fixed building services, taken from the published Direction

  • Annexes 6E and 6F deleted – information now within the Non-domestic Building Services Compliance Guide for Scotland.

6.0.14 Relevant legislation

EU Directive 2009/28/EC - Directive 2009/28/EC (http://europa.eu/legislation_summaries/energy/renewable_energy/en0009_en.htm) promotes the use of energy from renewable sources, including promotion within national legislation. It establishes a common framework for the use of energy from renewable sources in order to limit greenhouse gas emissions, including establishment of national action plans and targets which set the share of energy from renewable sources for 2020.

6.0.15 Certification

Scottish Ministers can, under Section 7 of the Building (Scotland) Act 2003, approve schemes for the certification of design or construction for compliance with the mandatory functional standards. Such schemes are approved on the basis that the procedures adopted by the scheme will take account of the need to co-ordinate the work of various designers and specialist contractors. Individuals approved to provide certification services under the scheme are assessed to ensure that they have the qualifications, skills and experience required to certify compliance for the work covered by the scope of the scheme. Checking procedures adopted by Approved Certifiers will deliver design or installation reliability in accordance with legislation.

The Certification of Design (Section 6 – Energy) for Non-domestic Buildings scheme has been approved by Scottish Ministers to confirm compliance with Section 6. Details are available on the certification pages of the Building Standards Division website http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards/profinfo/cert.