Overheating in new domestic buildings

Overheating in new domestic buildings

Window energy efficiency
Through its consultation ending on 26th November 2021, the Scottish Government has set out its proposed changes to Section 6 (Energy) of the Technical Handbooks for domestic and non-domestic buildings.

For new dwellings, the consultation proposes the introduction to Section 3 (Environment) of a new mandatory standard to assess and mitigate the summertime overheating risk.

Applying only to new dwellings, the new standard would require dwellings to be designed and constructed in such a way as to limit unwanted solar gains in summer. Two methods of assessment are foreseen:
  • Simplified method, related to orientation, glazing and floor area
  • Detailed thermal analysis method, involving calculation of the risk of overheating
Using the simplified method, for new residential buildings with a glazed area greater than 25% of the room floor area, shading (e.g. louvres, external shutters, etc.) should be provided. Alternatively, the glazing g value should be revised to reduce solar gain in proportion to the increase in glazed area above 25%. The latter should be based on heat gain no greater than an unshaded opening, 25% of the room floor area and a g value of 0.60.

Changes to the glass specification to reduce the g value should, where practicable, maintain a high light transmittance to minimise an adverse impact on daylighting. A light transmittance of 0.70 or higher is recommended in the proposals.

By implication, glazed areas of 25% or lower would not require shading or glazing with lower g value than 0.60 when using the simplified method.

To satisfy the above requirements, Pilkington offers a range of glass that can provide solar control and / or thermal insulation. This includes products that can achieve g values of 0.60 or lower, as stated in the simplified method.

If using the dynamic thermal analysis method to predict overheating risk, the methodology set out in CIBSE TM59 'Design methodology for the assessment of overheating risk in homes' should be followed.

Documents related to the consultation on proposed requirements for mitigating the risk of overheating in new dwellings 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.