Publication - Advice and guidance

Building Standards technical handbook 2017: 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: domestic buildings
7. Sustainability

7.1 Statement of sustainability

Mandatory Standard

Standard 7.1

Every building must be designed and constructed in such a way that:

  1. with regard to a dwelling or school building containing classrooms, a level of sustainability specified by the Scottish Ministers in respect of carbon dioxide emissions, resource use, building flexibility, adaptability and occupant well-being is achieved

  2. with regard to a non-domestic building other than a school building containing classrooms, a level of sustainability specified by the Scottish Ministers in respect of carbon dioxide emissions is achieved, and

  3. a statement of the level of sustainability achieved is affixed to the dwelling or non-domestic building.

Limitation:

This standard does not apply to:

  1. alterations and extensions to buildings

  2. conversions of buildings

  3. buildings that are ancillary to a dwelling that are stand-alone having an area less than 50 square metres

  4. buildings which will not be heated or cooled other than by heating provided solely for the purpose of frost protection

  5. buildings intended to have a life not exceeding the period specified in regulation 6, or

  6. conservatories.

7.1.0 Statement of sustainability (sustainability label)

The statement of sustainability (sustainability label, or SL) that includes the level of sustainability achieved must be fixed to the building prior to completion. The sustainability label should be indelibly marked and located in a position that is readily accessible, protected from weather and not easily obscured. A suitable location could be in a internal cupboard containing a utility meter or the owner may choose to display the label in a more prominent location. An example of an approved label with the overall level achieved on the left hand side and the levels achieved in each of the individual aspects of sustainability on the right hand side is given in Annex E. A program to generate such a label that is specific to a building can be accessed here: http://www.s7sust.co.uk/.

7.1.1 Levels of sustainability

The specified level of sustainability for a dwelling should be selected from the following:

  • Bronze or Bronze Active

  • Silver or Silver Active

  • Gold

The aim is for balance in the setting of upper levels because sustainability is considered in the round rather than focusing on issues of energy or carbon emissions clauses 7.1 — 7.1.1. Reaching upper levels should be a valid target for any new development, regardless of size or location. Generally, levels have been set to avoid individual aspects that could upset applications which might otherwise meet all of the other aspects of sustainability.

The first optional upper level ‘Silver’ offers substantial benefits in a range of sustainability aspects which should be achievable by a sector of the mainstream market. The second optional upper level ‘gold’ is a more demanding target, initially aimed at those intent on pursuing best practice.

Buildings that exceed a gold sustainability level are also welcomed. A third upper level called 'platinum' has been reserved for further recognition within the building standards system. At present, only the aspect of carbon dioxide emissions has been defined for this level.

Buildings that exceed Bronze, Bronze Active, Silver, Silver Active or Gold levels by achieving a higher level criteria in one or more of the aspects are welcome. This additional achievement will be reflected on the sustainability label. However the achievement of the next upper level will only be recognised once all aspects of that particular level have been included. The award of an overall upper level depends upon meeting all aspects, rather than allowing trade-offs to achieve a score, reinforcing the fact that sustainable outcomes rely on holistic integrated design.

The specified levels of sustainability in clauses 7.1.2 to 7.1.7, are sets of measures that are transparent to all including verifiers, planners, funding bodies, owners and tenants. To meet this standard, it should not be necessary to secure expert evaluation beyond that already used in the design to demonstrate compliance with the standards in Sections 1 to 6.

7.1.2 Bronze level

This is the baseline level for sustainability achieved where the dwelling meets the functional standards set out in Sections 1 – 6 of this Handbook.

7.1.3 Bronze Active level

This is the baseline level where the dwelling meets the functional standards set out in Sections 1 – 6 of this Handbook, but in addition the dwelling includes the use of a low and zero carbon generating technology (LZCGT) in respect of meeting Standard 6.1 within Section 6, Energy. This level is primarily to assist local authorities to meet their obligations under Section 72 of the Climate Change (Scotland) Act 2009 by identifying the use of LZCGT. In this respect, LZCGTs include: wind turbines, water turbines, heat pumps (all varieties), solar thermal panels, photovoltaic panels, combined heat and power units (fired by low emission sources), fuel cells, biomass boilers/stoves and biogas.

7.1.4 Silver level

A dwelling at this first optional upper level should meet all the standards in Sections 1 – 6 that apply to the building for the Bronze level and, in addition, the dwelling should comply with the Silver level in each of the eight aspects below.

Aspect Silver level 1: Carbon dioxide emissions

All new dwellings that meet or exceed the Target Emissions Rate (TER) detailed in Section 6, Energy of this Handbook, will automatically meet the Silver level criteria in respect of CO2 emissions. This is due to the 21% improvement on the 2010 standards that occurred in October 2015.

Aspect Silver level 2: Energy for space heating

Maximum annual demand for useful energy for space heating should be:

  • 40kWh/m2 for houses, or

  • 30kWh/m2 for flats or maisonettes

To assess, the output from box no.99 of the SAP 2012 DER worksheet should be no more than the figures above.

Aspect Silver level 3: Energy for water heating

At least 5% of the dwelling or domestic building’s annual energy demand for water heating should be from:

  • heat recovery and/or renewable sources with little or no associated fuel costs (e.g. solar thermal water heating and associated storage or heat recovery from greywater) that are allocated for water heating.

To assess, the annual energy demand for water heating in kWh multiplied by 0.05, should be no more than the contribution from specified equipment that uses renewable energy and/or heat recovery. A SAP spreadsheet is available for this calculation here: http://www.bre.co.uk/sap2012/page.jsp?id=3817.

Where a building contains more than one dwelling (such as a block of flats or terrace of houses) the average annual energy demand for water heating may be met by installations of renewable sources and/or heat recovery for the block. This is similar to the buildings with multiple dwellings guidance in Section 6.

Aspect Silver level 4: Water use efficiency

Enhanced or additional products should be provided as follows:

  • WCs of average flush volume not more than 4.5 litres

  • Wash hand basin taps with a flow rate not more than 6 l/m

  • shower heads with a flow rate not more than 8 l/m, and

  • 1 water butt (with a min. capacity of 200 litres) for outdoor use per dwelling. Dwellings without a private garden or landscaped area, or if there is no access to rainwater collection (for example if there is no external rainwater pipe within the curtilage) are excluded.

The flow rates referred to align with performance bands in the Bathroom Manufacturers Association’s water efficient product labelling scheme (BMA scheme). Reference can to be made to the performance bands within the BMA scheme or equivalent standards. Kitchen or utility room sinks are not included in low flow fitting targets at this level.

Consideration should be given to the flow rates that combi boilers (if fitted) need to activate their water heating function when specifying taps and shower heads with lower flow rates.

When installing low volume flush WCs, the pipe diameter and gradient inter-relationship is critical in order that the new and any existing sections of the drain are self-cleansing.

Aspect Silver level 5: Optimising Performance

  1. Quick start guide: Provide guidance to the occupants on the ways in which the specific dwelling is intended to function and how to optimise its performance on the scope, format and contents of the guide for occupants. Supplementary guidance with a performance specification as well as links to an example completed quick start guide is in Annex B.

    This is additional to the written information to be provided to occupants under Section 6.

  2. Resource use display: Install a real-time resource use monitor that displays electricity use, located in an easily accessible and readable position.

Aspect Silver level 6: Flexibility and Adaptability

Provide a home office space dedicated for home working/study to include:

  • A clear space, against a wall or partition, where a desk of 1800mm long x 600mm deep could be placed. Alternatively, the desk space could be ‘L’ shaped in plan as long as each leg of the ’L’ is a minimum length of 1200mm. Diagrams below show the two desk options with associated activity spaces.

  • 2 switched electrical sockets in addition to those that should be provided under Section 4.

  • A connection to allow direct access to internet services (unless such a provision is made elsewhere in the dwelling).

  • For natural daylight there should be line of sight to a window, glazed external door or rooflight.

  • Generally ventilation, accessibility, safety and escape should meet all the other standards however, see paragraphs below.

For diagram, see Annex C.

In any dwelling, the home office space can be in a circulation space but should not be located in a protected enclosure. The desk space and/or its activity space can locally reduce a corridor width to 800 mm and should not interfere with door swings.

In any dwelling, the home office space can occupy a room by itself even if this room is too small to be an apartment. In this case, this small room should be ventilated as if it were an apartment.

In any dwelling, the home office space can occupy a part of the enhanced apartment but the desk space and its activity space should be additional to the defined spaces and access of the enhanced apartment, as described in guidance in Section 3.

In any dwelling the home office space can be in a room that includes the kitchen but the desk space and or its activity space should not interfere with kitchen worktops, appliances or manoeuvring spaces.

To allow some more flexibility in smaller dwellings (those of not more than 2 apartments) the home office space can be in any apartment. But in this case, the desk space and its activity space should not overlap with the minimum furniture provision or associated activity spaces.

The height of the home office should be not less than 1.8m over the activity space and 1.5m over the desk space. For dwellings over 150m2 floor area, two home office spaces should be provided.

Aspect Silver level 7: Well-being and security

  1. Noise separation: Design performance levels for separating walls and separating floors associated with attached dwellings should be:

    • Minimum airborne sound insulation: 58 dB DnT,w

    • Maximum impact sound transmission: 54 dB L'nT,w

    Performance levels for noise isolation for separating walls and separating floors should be verified by carrying out a sound test as indicated in the guidance to Section 5.

  2. Noise reduction between rooms: Design performance level for a minimum airborne sound insulation should be 44 dB Rw.

    This refers to all internal partitions in all dwellings and intermediate floors within houses and maisonettes excluding storage cupboards and should be substantiated by manufacturer’s laboratory test certificates.

  3. Enhanced natural lighting: The enhanced apartment should be provided with a glazed area of not less than 1/8th of the floor area of the apartment.

  4. Security: Install a 13 amp fused spur, suitable for an intruder alarm system, located within 2m of the main entrance door.

Aspect Silver level 8: Material use and waste

Recycling of solid waste: Provide a dedicated internal space with a volume of at least 0.12m3(120 litres) and no dimension less than 450mm, for storing recyclable material.

The storage space should:

  • be able to store small amounts of recyclable material (e.g. metal, glass, plastic, cardboard and/or paper)

  • be easily cleanable

  • be additional to the general 1m3 kitchen storage in Section 3, and

  • facilitate temporary storage before transfer to a main storage point or a collection point, whether for the dwelling or for a group of dwellings.

It is recognised that local authority provision, resources and preferences for collecting separately or together will vary across Scotland. Therefore subdivision into containers for different materials is optional.

7.1.5 Silver Active level

This is the same as the silver level but, in addition, the dwelling includes the use of a low and zero carbon generating technology (LZCGT) in respect of meeting at least one of the aspects: Silver 1, Silver 2 or Silver 3. This level is primarily to assist local authorities to meet their obligations under Section 72 of the Climate Change (Scotland) Act 2009 by identifying the use of LZCGT. In this respect, LZCGTs include: wind turbines, water turbines, heat pumps (all varieties), solar thermal panels, photovoltaic panels, combined heat and power units (fired by low emission sources), fuel cells, biomass boilers/stoves and biogas.

7.1.6 Gold level

A dwelling at this second optional upper level should meet all the standards in Sections 1 – 6 that apply to the building for the bronze level and in addition the dwelling should comply with the gold level in each of the eight aspects below.

Aspect Gold level 1: Carbon dioxide emissions

Under the guidance to Standard 6.1, the carbon dioxide emissions (Dwelling Emission Rate) is to be 27% lower than the Target Emission Rate set by the 2015 Standards.

To establish this, the TER from SAP 2012 calculation should be multiplied by 0.73, to give a revised figure which the DER should not exceed (this is equivalent to a 42.8% improvement on the 2010 Standards and a 60% improvement on the 2007 Standards).

Where a building contains more than one dwelling (such as a block of flats or terrace of houses) the average carbon dioxide emissions for the proposed block or terrace (DER) may be compared to the average target CO2 emissions (TER) for the ‘notional block or terrace', similar to guidance in Section 6.

Aspect Gold level 2: Energy for space heating

Maximum annual demand for useful energy for space heating should be:

  • 30 kWh/m2 for houses, or

  • 20 kWh/m2 for flats or maisonettes

To assess, the output from box no.99 of the SAP 2012 DER worksheet should be no more than the figures above.

Aspect Gold 3: Energy for water heating

a. Renewables and heat recovery: At least 50% of the dwelling or domestic building’s annual energy demand for water heating should be from:

  • heat recovery and/or renewable sources with little or no associated fuel costs (e.g. solar thermal water heating and associated storage or heat recovery from greywater) that are allocated for water heating.

To assess, the annual energy demand for water heating in kWh multiplied by 0.5, should be no more than the contribution from specified equipment that uses renewable energy and/or heat recovery. A SAP spreadsheet is available for this calculation here: http://www.bre.co.uk/sap2012/page.jsp?id=3817.

Where a building contains more than one dwelling (such as a block of flats or terrace of houses) the average annual energy demand for water heating may be met by installations of renewable sources and/or heat recovery for the block. This is similar to the buildings with multiple dwellings guidance in Section 6.

b. Water heating display: A display showing the performance of the primary renewable source, such as a solar collector, should be mounted in easily accessible space, for instance alongside controls for heating equipment or near the bathroom/shower room door.

Aspect Gold 4: Water use efficiency

Enhanced or additional products should be provided to encourage water efficiency as follows:

  • 1 water butt (with a min. capacity of 200 litres) for outdoor use per dwelling. Dwellings without a garden or landscaped area, or if there is no access to rainwater collection (for example if there is no external rainwater pipe within the curtilage) are excluded, and

  • 3 of the following 5 items:

    • water meter

    • WCs of average flush volume to be not more than 3.5 litres

    • wash hand basin taps of flow rates not more than 4 l/m and to kitchen or utility room sinks to be not more than 6 l/m

    • shower heads with maximum flow rate not more than 6 l/m

    • rainwater harvesting or greywater recycling system designed to provide water for toilet flushing.

    The flow rates referred to align with performance bands in the Bathroom Manufacturers Association’s water efficient product labelling scheme (BMA scheme). Reference can be made to the performance bands within the BMA scheme or equivalent standards.

    Consideration should be given to the flow rates that combi-boilers (if fitted) need to activate their water heating function when specifying taps and shower heads with lower flow rates.

    When installing low volume flush WCs, the pipe diameter and gradient inter-relationship is critical in order that the new and any existing sections of the drain are self-cleansing.

    Aspect Gold 5: Optimising Performance

    a. Quick start guide: Provide as for Aspect Silver 5, plus: Direct ‘easy release’ adhesive labels on all key heating and ventilation equipment including (where fitted): trickle ventilators, extract fans, mechanical ventilation with heat recovery (MVHR), heating controls (programmers, Thermostatic Radiator Valves (TRVs)). Supplementary guidance on the content of the direct equipment labels is in Annex B.

    b. Resource use display: Provide as for Aspect Silver 5, plus the real-time resource display indicates gas use (if gas is used for heating), displaying gas use at least at a daily period.

    Aspect Gold 6: Flexibility and adaptability

    a. Home office: Provide as for Aspect Silver 6.

    b. Mobility space: Provide convenient secure mobility space to accommodate an electric wheelchair(s) and that could also be suitable for pram storage and the storage of a bicycle(s). The size is defined as follows:

    • An electric wheelchair (or pram) storage space of: 0.8m x 1.1m on plan, minimum height of 1.8m. For dwellings of 4 apartments or more; or over 150m2; space for two electric wheelchairs and

    • A bicycle storage space of: 2m x 0.75m on plan, minimum height of 1.2m. For dwellings of 3 apartments or more; or over 150m2; space for two bicycles: 1m x 1.5m.

    A single infant’s pram or pushchair should generally be able to use the mobility space as defined by either the cycle or wheelchair footprint. The space does not need to be able to store a wheelchair at the same time as a pram or bicycle; this diagram shows how the spaces can overlap.

    For diagram, see Annex D.

    The mobility space should have a socket outlet for recharging. Ideally, it should be adjacent to the accessible entrance. It should not be located in a protected enclosure and it should be outwith the minimum corridor width noted in Section 4, clear of any door way, door swing, stair landing or space identified for a future stairlift installation.

    The mobility space in the dwelling would be defined only by the wheelchair size(s) if either of the areas below are present, allowing the bicycle storage provision to be located outwith the dwelling:

    • A motor vehicle garage could be adequate as long as bicycle storage is outwith a 4.8m x 2.4m space for parking a single motor vehicle or

    • Communal bicycle storage that is secure (locked with resident only key access) and weather protected. This should be sized on the number of apartments in total or overall size of all dwellings served. The communal store should be at ground level or accessible by a ramp.

    If separate bicycle storage is allocated (garage or communal store), this does not need an electrical socket outlet. The storage provision for more than one bicycle could be split between a dwelling and a communal store.

    c. General storage provision within a dwelling: Accessible storage of 1m3 in volume per apartment. The storage space should be capable of being closed off with a door but does not need to be off each apartment.

    General storage is in addition to a wardrobe space or built-in wardrobe, or storage that is designated for the future provision of a shower. Both of these are identified in Section 3.

    Aspect Gold 7: Well-being and security

    a. Noise separation: Design performance levels for separating walls and separating floors associated with attached dwellings should be:

    • Minimum airborne sound insulation: 60 dB DnT,w

    • Maximum impact sound transmission: 52 dB L'nT,w

    Performance levels for noise isolation for separating walls and separating floors should be verified by carrying out a sound test as indicated in the guidance to Section 5.

    b. Noise between rooms: Design performance level for a minimum airborne sound insulation should be 45 dB Rw.

    This refers to all internal partitions in all dwellings and intermediate floors within houses and maisonettes excluding storage cupboards and should be substantiated by manufacturer’s laboratory test certificates.

    c. Enhanced natural lighting: Provide as Aspect Silver 7 plus the average daylight factor (average DF) for kitchens and living room/dining/study should be 1.5% and 2% respectively, using the simplified calculation below.

    The DF is a factor, expressed as a percentage, that will rise or fall depending on the relationship of glazed area and room dimensions. Here it is simplified as an average for a particular room. Matters pertaining to overshadowing, neighbouring buildings or orientation are removed from this calculation.

    Average DF% = (52 x M x W) / A

    Where:

    A = The sum of the area of all room surfaces (ceiling, floor, walls, doors, windows and rooflights), in m2.

    M = Correction factor for dirt or ease of cleaning, consisting of:

    • 1.0 for vertical glazing or

    • 0.8 for sloping glazing or

    • 0.7 for horizontal glazing.

    W = Glazed area of windows or rooflights, taking account of framing, in m2. Measure glazed panes or measure window area including frames then multiply by:

    • 0.9 for metal frames (patent glazing) or

    • 0.8 for metal frames (large pane) or

    • 0.7 for timber frames (large pane) or

    • 0.6 for timber frames (‘Georgian’ pane).

    Assume the factors for PVC framed windows are equal to timber.

    d. Security: Provide as Aspect Silver 7 plus:

    • provide doorsets and windows which are tested and certified by a notified body as meeting a recognised standard for security or

    • install a full intruder alarm system that complies with BS EN 50131 and PD6662 (wired system) or a Class VI alarm to BS 6799 (wire free system) that conforms to Association of Chief Police Officers (ACPO) guidelines.

    e. Outdoor space: Provide private or communal outdoor space with room for occupants to sit outside. The outdoor space should be accessible only to occupants of designated houses or flats and not be occupied by car or cycle parking space, waste storage area, electricity substations or other ancillary features. It must comprise of at least one of the following:

    • a private garden, patio, roof terrace or balcony (with the front open to air, or see Note 1 below) of an area no less than 1.5m2/apartment (minimum 3m2/home) with a minimum short dimension of 1.2m or

    • a communal shared garden or courtyard that is:

      • of an area no less than 1.5m2/apartment (minimum 3m2/home) with a minimum short dimension of 2m

      • secure by, for example, resident only key access

      • secluded and fully enclosed with buildings themselves, walls, fencing or planting are all permitted possibilities to define the space.

    Generally issues of daylight, ventilation, safety and escape should meet the guidance of all the other mandatory standards. Access to these spaces should follow the guidance of Section 4.

    Note 1: In a studio or single bedroom flat (i.e. a flat with 2 apartments or less) then the balcony could be a ‘Juliet’ type where the size could then be provided by a space immediately inside of an inward opening glazed door or door(s) and has a protective barrier externally. This space should not:

    • interfere with the defined space or access of an enhanced apartment

    • overlap with minimum furniture provision or associated activity spaces and

    • interfere with kitchen worktops, appliances or manoeuvring spaces.

    Aspect Gold 8: Material use and waste

    a. Recycling of solid waste: Provide as for Aspect Silver 8.

    b. Design for de-construction: By consideration of waste minimisation arising from the built-form, one of the following should be adopted:

    • Demonstrate that key principles of demountable construction detailing have been followed. This could be demonstrated by submitted drawings containing reference to guidance such as the Scottish Ecological Design Association’s (SEDA) document on: 'Design and Detailing for Deconstruction'. A minimum of three of the high or medium priority items from the example constructions in the detailed section of this document should be demonstrated clearly or

    • Provide a detailed plan for deconstruction of the building that follows a template such as that on page 21 of the SEDA document. This option provides opportunities to meet this level in this aspect for prefabricated, modularised or flexible internally partitioned constructions that use techniques that involve off-site manufacturing where the described assembly could be reversed for disassembly or

    • An option only where a site is occupied and the warrant application is for demolition and construction. Provide a pre-demolition audit of existing buildings/structures on site. In this option for brownfield developments only, the audit should follow an established methodology such as the ICE Demolition Protocol, referred to by the Waste and Resources Action Programme (WRAP) that:

      • produces a Bill of Quantities of the different materials in the building to be demolished

      • identifies the tonnages of material that can be recovered and

      • determines the percentage of materials recoverable.

7.1.7 Carbon dioxide emissions only at Platinum level

All the standards in Sections 1 - 6 that apply to the building for Bronze level, and in addition the building should comply with the following.

Aspect Platinum 1: Carbon dioxide emissions

Under the guidance to Standard 6.1, carbon dioxide emissions CO2 Dwelling Emission Rate (DER) is to be 100% lower than the Target Emission Rate (TER) set by the 2010 Standards. To establish this, the DER should not exceed zero. (This net zero carbon equivalent is a 100% improvement on the 2007 Standards).

Where a building contains more than one dwelling (such as a block of flats or terrace of houses) the average carbon dioxide emissions for the proposed block or terrace (DER) may be compared to the average target CO2 emissions (TER) for the ‘notional block or terrace', similar to guidance in Section 6.

Aspect Platinum 2: Energy for space heating

[not currently defined]

Aspect Platinum 3: Energy for water heating

[not currently defined]

Aspect Platinum 4: Water use efficiency

[not currently defined]

Aspect Platinum 5: Optimising Performance

[not currently defined]

Aspect Platinum 6: Flexibility and Adaptability

[not currently defined]

Aspect Platinum 7: Well-being and Security

[not currently defined]

Aspect Platinum 8: Material use and waste

[not currently defined]