Scottish Building Standards Section 6

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From today, 1st October 2015, Scottish construction will take a significant step closer to Zero carbon building, with the introduction of new 2015 versions of the building standards incorporating a significant uplift in requirements for Section 6 for both Domestic and Non-domestic buildings, alongside a new Section 7 – sustainability.

The changes represent a 21% improvement in domestic standards and a 43% improvement for non-domestic buildings against the 2011 standards levels and signpost a potential path for future nearly zero energy building that the rest of the UK could follow.

Domestic (New build)
For new domestic properties in Scotland, the aggregate uplift is 21% over the previous 2011 standards, which incorporates a strong building fabric core, alongside good services and in most cases, likely some renewable technology level to achieve.

As in the 2011 Standards, the Dwelling Emission Rate (DER) must not exceed the Target Emission Rate (TER). The TER is directly defined by an elemental specification for fabric and building services based on the chosen fuel type and following this to the letter allows compliance via the ‘simplified approach’.

The notional building recipe has been set with an improved fabric performance, alongside tightened limiting backstop U–values if deviating from the simplified approach. These improved levels, which can be seen below set a much stronger baseline for the thermal performance of the building envelope, whilst the backstops ensure that even where deviating from the simplified approach, a strong fabric is still mandated.

Element Previous Simplified approach target (2011) Previous Limiting Backstop Value (2011) Simplified approach target (2015) Limiting Backstop Value (2015)
Roof (W/m²K) 0.13 0.18 0.11 0.15
External Wall (W/m²K) 0.19 0.25 0.17 0.22
Floors (W/m²K) 0.15 0.20 0.15 0.18
Party Walls (W/m²K) 0.20 0.20 0.00 0.20
Windows & Doors (W/m²K) 1.50 1.80 1.40 1.60

Notional building targets and Limiting Backstop Fabric Parameters

From SAP modelling undertaken using the Scottish version of SAP2012, the levels required to achieve compliance for a typical dwelling may need to be improved upon depending on the services and renewable technology levels proposed for a given dwelling. Floors, air tightness and thermal bridging are all areas that can be easily improved upon compared to the notional specification to reduce the servicing or renewables requirements whilst reducing overall heating demand.

Domestic Retrofit & Extensions
Several aspects of the domestic refurbishment standards have also been tightened. Where new fabric elements are required for refurbishments such as extensions, the minimum U-value performance for these elements is now set at a more stringent level and the targets for upgraded existing elements have also been tightened.

Element Extensions (Where existing dwelling walls and roof are worse than 0.70 and 0.25 respectively) Other extensions; Upgraded existing elements; Non-exempt conservatories
Walls (W/m²K) 0.17 0.22
Floors (W/m²K) 0.15 0.18
Pitched Roof (W/m²K) 0.11 0.15
Flat Roof (W/m²K) 0.13 0.18
Windows, doors, rooflights (W/m²K) 1.40 1.60

Extensions and upgraded elements targets

Compensatory approaches may be used to vary from the above values, provided individual elements are no worse than the limiting ones.

Non Domestic (New Build)
More significant changes are incorporated within the regulations for new non-domestic properties. A 43% aggregate improvement over previous standards has been introduced.
The TER is defined by a new Notional Building Specification which varies depending on whether the building will be heated and naturally ventilated, or whether mechanically ventilated or cooled; simple compliance can be achieved if the notional specification is followed; however there is opportunity in deviating from this approach and an improved fabric performance can offer a simpler approach to compliance.

Element Zone heated & naturally ventilated Zone heated & mechanically ventilated / cooled
Roof (W/m²K) 0.18 0.16
Wall (W/m²K) 0.23 0.20
Floor (W/m²K) 0.22 0.20
Window (W/m²K) 1.8 (10% FF) 1.6 (10% FF)
Rooflight (W/m²K) 1.8 (15%FF) 1.8 (15%FF)
Vehicle access & similar large doors (W/m²K) 1.5 1.5
Pedestrian doors & high usage entrance doors (W/m²K) 2.2 2.2
Air Permeability (m³/m²/hr @ 50 Pa.) 5 3

Notional building targets for non-domestic new build
Shell buildings have also been revised in their requirements, with maximum area-weighted U-values set for a staged building warrant that ensures that the building fabric should be appropriate for the buildings fitted out end use.
For various further details refer to the building standards, or our helpful guide for non-domestic buildings.

Non domestic extensions and retrofit
The new non–domestic standard sets out area weighted average U–value standards and individual element U–values for refurbishment or conversion of heated and unheated buildings and also sets out requirements for extensions to the insulation envelope.

Element Extensions and retrofit of unheated buildings (area weighted requirement) Conversion of Heated Buildings Limiting Backstop Values for individual elements
Roofs (W/m²K) 0.15 0.25 0.35
Walls (W/m²K) 0.25 0.30 0.70
Floors (W/m²K) 0.20 0.25 0.70

Targets for non-domestic extensions and upgraded retained elements

As with the domestic requirements, compensatory approaches may be used to vary from the above values, provided individual elements are no worse than the limiting ones.

A bold step forwards
The new Scottish Building Standards Regulations take a bold step forward towards nearly zero energy building and achieving the levels of aspiration that are required to be met if we are to stand any chance of achieving our climate change commitments. The new standards emphasise the central role that the building fabric must play in any long term strategy to reduce carbon dioxide emissions from buildings, whilst also dragging into the mainstream the idea that a coordinated approach is needed to go further.

There’s more information on the Scottish Executive’s building standards website and our new guides to the regulations can be found on the Building Regulations page of our website knowledge base.

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