Glossary
Approved Document L
Approved Document L gives practical guidance on energy efficiency (Part L) of the Building Regulations in England — insulation, heating systems, lighting and carbon targets for new work and extensions.
Designers use it to show compliance; SAP or other calculations are often required for larger projects.
Wales publishes its own Part L documents. Scotland and NI set energy standards in their technical handbooks/booklets.
Official source: Approved Document L (GOV.UK). Checked 27 October 2026.