Section 6 Energy 2021 – Existing Homes

2 December 2021 Kingspan Insulation UK

Scotland is facing a major retrofit challenge over the next couple of decades with more than half of the existing housing stock needing upgrades to reach the goal of raising all homes to an EPC rating of C by 2040. The update to Section 6 (Energy) of the Building Standards, due to come into force next year, is an opportunity to help drive this work forward. Here are some of the key changes expected in the revised document. 

New minimum fabric limits

The Scottish consultation proposes tightening the fabric backstop requirements for extensions, alterations and conversions to the same requirements as those for new build. This marks a change from the existing requirements which are separated into two categories depending on the thermal performance of the walls and roof (as shown in the table below).

The final requirements will depend on which of the two carbon emissions options proposed in the Section 6 new build consultation are adopted, however both options represent a significant, but achievable, upgrade over the existing requirements.

Element type Current (2015) U-value existing walls <0.7 W/m2K & roof <0.25 W/m2K Current (2015) U-value existing walls ≥0.7 W/m2K & roof >0.25 W/m2K 2022 Option 1- improved 2022 Option 2- advanced
Horizontal ceilings (W/m2K) 0.11 0.15 0.12 0.11
Sloping and flat roofs (W/m2K) 0.13 0.18 0.12 0.11
Walls (W/m2K) 0.17 0.22 0.17 0.16
Floors (W/m2K) 0.15 0.18 0.15 0.13
Windows (W/m2K) 1.40 1.60 1.40 1.20
Rooflights (W/m2K) 1.40 1.60 1.90 1.70
Doors with glazing (W/m2K) 1.40 1.60 1.40 1.20

The consultation also states that project teams should be strongly encouraged to target these values when undertaking other refurbishment work on the building envelope. However, when refurbishing existing elements, they will still have the option to simply aim for compliance with somewhat lax threshold values set at 0.70 W/m2K for walls and floors and 0.35 W/m2K for roofs (where there is a strong economic or technical reason why they cannot go further).

Preparing for switch to low carbon heating

To support a smoother transition to low carbon heating systems which operate most efficiently at lower flow temperatures, the Scottish consultation recommends that where a wet heating system is replaced in an existing building (including both the generator and emitters), the new system should be designed and sized to allow them to operate effectively with a mean water temperature of 55 °C.

Additionally, if no thermostat is currently present, one will need to be installed at the point the boiler (or other generator) is replaced.

In addition to these changes, it’s important to keep in mind the potential limitations of heat pumps. As outdoor temperatures drop, the efficiency of these devices drops and it may be necessary to ‘top-up’ demand with direct electricity. This has the potential to significantly raise heating costs, risking pushing some households into fuel poverty. To avoid this, it is important to ensure all areas of the building fabric are well insulated, limiting heating demand.

Introduction of major renovation

The consultation recommends introducing the term ‘major renovation’ into the updated Section 6. This will function similarly to the ‘consequential improvements’ for non-domestic buildings, where significant work on a building triggers additional assessments or works. It is proposed that this will apply where “more than 25% of the surface of the building envelope undergoes renovation”. 

Initially, this is only relevant for buildings with more than 10 parking spaces, requiring electrical vehicle charge points to be installed in as many spaces as possible subject to exemptions. In the future, however, this mechanism may be used to trigger other improvements.


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