Technical guidance
Practical guidance on energy, overheating, certificates and construction evidence.
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12 articles
Energy and overheating
Part L and Part O are separate requirements in England, but their most important design inputs overlap. Coordinating them early gives the project more usable choices.
Read guidance : Why Part L and Part O should be designed togetherHow EASOB scheme requirements relate to new-home and commercial EPC records, Part L photographs and assessment quality checks.
A practical guide for site teams preparing a new dwelling for air-permeability testing, with the drawings, details and records that need to stay aligned.
A practical guide to coordinating sanitaryware, flow rates, appliance data and the water-efficiency calculation for a new dwelling in England.
A practical starting point for projects that may need sound-insulation testing, covering scope, programme, room condition and the evidence the team should retain.
Commercial EPC assessment levels reflect building and services complexity, not a simple size or use-class shortcut.
Extensions in England can require a project-specific energy calculation where glazing or other design choices go beyond a straightforward elemental route.
The 2026 Approved Document L has been published, its main effective dates are in 2027, SAP 10.3 is the initial methodology and the Home Energy Model will follow later.
The June 2026 interim response proposes a targeted EPC B standard for larger private rented non-domestic buildings, but legislation is still required.
New-dwelling Part L evidence in England needs identifiable, plot-specific photographs taken at the right construction stage and checked against the assessed design.
SAP assesses dwellings, SBEM covers many non-domestic compliance cases, and dynamic simulation can answer more detailed time-based performance questions.
An EPC is commonly needed when a building is constructed, sold or let, but exemptions, building use and the type of assessment all matter.
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