New and existing domestic buildings
The Scottish Government has published changes to Section 6 (Energy) of the Technical Handbooks for domestic and non-domestic buildings to take effect on 1
st February 2023 (deferred from 1
st December 2022).
Changes in Section 6 on energy are intended to deliver 32% aggregate reduction in CO
2 emissions on 2015 standards for domestic buildings. A dwelling must achieve the overall Target Dwelling Emissions Rate and Target Dwelling Delivered Energy Rating.
For new domestic buildings, there are changes to the maximum (limiting) U values for fabric elements. However, the expectation is that the U value will have to be lower than this to enable new dwellings to achieve the overall targets. The notional dwelling specification used to determine the overall targets is based on the following U values of fenestration elements:
| Fenestration element |
Specification
(W/m2K) |
| Doors |
1.2 |
| Windows |
1.2 |
| Roof Windows |
1.2 |
| Rooflights (in horizontal position) |
1.7 |
The maximum U values for fenestration elements of dwellings (including extensions and existing dwellings) are summarised below:
| Fenestration element |
Maximum U value
(W/m2K) |
| Windows and doors |
1.4
or
Window Energy Rating (WER) or Doorset Energy Rating (DER)
minimum band B |
| Rooflights (in horizontal position) |
2.1 |
The above values are for new and existing dwellings, with the exception that WER / DER apply only to existing dwellings (e.g. replacement windows and doors).
Where replacement work relates only to one or two replacement windows or doors, to allow matching windows or doors to be installed, the frame may be disregarded for assessment purposes provided the centre pane U value for each glazed unit is 1.2 W/m2K.
For secondary glazing, an existing window, after alteration should achieve a U value of about 3.5 W/m2K.
Pilkington manufactures a range of low emissivity glass for thermal insulation that can help windows and doors to achieve low U-values.
The 2022 editions of the Technical Handbooks can be found here.
If you have any questions on changes and what the implications might be for glass, please complete our online contact form, selecting 'Architect' or 'Trade' as the Nature of Enquiry and 'Other' as the Enquiry Type.
Please state 'Technical Handbook Section 6' in the Question / Comment box when completing the form.