Scottish Building Standards 2015 – Overview of the Non-Domestic requirements

Scottish boy with the flag of Scotland

Following the Scottish government’s release of the 2015 building standards 12 months ahead of their implementation (October 2015), this blog post considers the changes to new build non-domestic requirements and touches on extensions and retrofit for non-domestic too…

Both the domestic and non domestic standards are available at:

Non-Domestic New Build

As with the current 2013 technical handbook requirements, the National Calculation Methodology (NCM) is to be used within an approved tool, typically SBEM, to create a notional building package from which a Target Emissions Rate (TER) is generated. This is based on an improved notional fabric and services specification over previous requirements (and includes an element of electrical generation based on 4.5% of floor area);

A Building Emission Rate (BER) is then calculated based on actual/proposed building performance compared against the notional building target. The actual specification can vary from the notional, provided the calculated BER is better than the TER and the limiting requirements are met.

In addition to improving the building fabric performance values used to set the target performance of the notional building, the new non-domestic Standards also provide greater flexibility, allowing heated buildings to be separated into zones depending on whether they are naturally or mechanically ventilated.

Heated and Naturally Ventilated Mechanically Ventilated/ Cooled
Roof (W/m2.K) 0.18 0.16
Wall (W/m2.K) 0.23 0.20
Floor (W/m2.K) 0.22 0.20

Figure 1. ‘Notional’ building – fabric U-values for TER setting

Fabric performance has been strongly supported with tightened area weighted average limiting U-values, particularly for shell-and-fit buildings, where the lower targets reflect the uncertainty of future use.

Area weighted average

U-value limit

Area weighted average

U-value limit – Shell buildings

Individual element

limiting U-value

Walls (W/m²K) 0.27 0.23 0.70
Roof (W/m²K) 0.20 0.15 0.35
Floor (W/m²K) 0.22 0.20 0.70

Figure 2. Limiting Backstop Fabric Parameters

So what about extensions and retrofit?

The requirements for converted and extended non-domestic buildings remain relatively unchanged from the 2013 technical handbook, however large extensions must comply with the new build Standards.

Type of Element Area weighted average U-values for small extensions, alterations to buildings and reconstructed existing elements (W/m²K) Individual element U-value (W/m²K)
Walls 0.25 0.7
Floors 0.2 0.7
Roofs 0.15 0.35
Windows, doors, rooflights 1.6 3.3

Figure 3. Maximum U-values for small extensions, alterations to buildings and reconstructed existing elements and limiting values

Overall, the Scottish targets are quite demanding, with a renewed focus on building fabric performance and tough new carbon emissions targets.

This a strong step towards low/zero carbon buildings, which will be less expensive to operate and with lower emissions associated with their construction.  Reduced energy demand, combined with a strong agenda towards decarbonisation of electricity generation is a solid step forwards, that the rest of the UK needs to follow!

Other blog posts on the new 2015 standards are available via the following links:

New build domestic

Domestic retrofit and extensions

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Jon Ducker is a qualified energy assessor working for Kingspan Insulation Ltd. He has an extensive knowledge of energy efficiency, renewable energy systems and sustainability in buildings with an expert knowledge of the relevant sections of buildings regulations and standards and their interactions with SAP. He provides authoritative advice regarding energy assessments for a wide range of public and private sector clients.

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