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 20% aggregate reduction in CO
2 emissions on 2015 standards for non-domestic buildings. A dwelling must achieve the overall Target Building Emissions Rate and Target Building Delivered Energy Rating.
For new non-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 buildings to achieve the overall targets. The notional building specification used to determine the overall targets is based on the following U values of fenestration elements:
| Fenestration element |
Specification
(W/m2K) |
| Windows and pedestrian doors |
1.2 (10% frame factor)
g value 50%
light transmittance 77% |
| Rooflights (in horizontal position) |
1.9 (15% frame factor)
g value 52%
LT 57% |
The maximum U values for fenestration elements of buildings (including extensions and existing buildings) are summarised below:
| Fenestration element |
Maximum U value
(W/m2K) |
| Windows and roof windows |
1.6
or
Window Energy Rating (WER) or Doorset Energy Rating (DER)
minimum band B |
| Rooflights (in horizontal position) |
2.2 |
Pedestrian doors
|
1.4 |
The above values are for new and existing building, with the exception that WER / DER apply only to existing buildings (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/m
2K.
For secondary glazing, an existing window, after alteration should achieve a U value of about 3.5 W/m
2K.
There is no maximum U value for display windows.
Pilkington manufactures a range of low emissivity glass for
thermal insulation that can help windows and doors to achieve low U-values.
Where a low g value is required, Pilkington provides a range of
solar control glass for reducing solar gains in buildings, while maintaining high levels of daylight.
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.