Knowledge base

Part L guides

Written by the consultants who run the calculations — every regulatory statement traced back to the Regulations, the Approved Documents or a Government circular.

Exploded view of a modern dwelling showing insulation, glazing and floor layers

6 guides

Part L, explained properly.

Answer-first guides for developers, self-builders and design teams. Where a figure is still unconfirmed against a primary source, we say so rather than publish it.

Part L 2026 explained: the Future Homes and Buildings Standards

What the 2026 edition of Approved Document L actually changes, when each part bites, and what it means for schemes being designed now.

11 min read

Part L transitional arrangements: which standard applies to your build

The transitional rules decide whether a plot is assessed under Part L 2021 or Part L 2026. They apply building by building — and that catches people out.

9 min read

SAP calculations explained: design stage to as-built

What a SAP calculation actually tests, what your assessor needs from the drawings, and how the design-stage submission connects to sign-off.

12 min read

SBEM calculations and BRUKL reports explained

The non-domestic side of Part L: what SBEM models, what a BRUKL report shows, and what building control expects at each stage.

10 min read

As-built Part L: the evidence pack building control expects

The evidence that turns a finished plot into a signed-off plot — and the site habits that stop it becoming a scramble at hand-over.

9 min read

Part L for extensions: the glazing allowance and how compliance works

Why a glazed rear extension often needs a calculation, how the 25% allowance is worked out, and what your options are when the design goes past it.

8 min read

Not sure which calculation you need? Send the drawings.

Tell us the project type and stage and we will confirm which assessment applies — and give you a fixed written fee.

020 3092 8551

No obligation, and no instant online price. Part L work is quoted from the drawings.

Awais Sarwar, MSc — Accredited Energy Assessor

Awais is an accredited domestic and commercial energy assessor and the owner of Team EPC Ltd, which trades as Part L Consultant. He has surveyed and lodged EPCs across flats, houses, HMOs, managed portfolios and commercial premises throughout London and the Home Counties, and is currently studying an MSc in philosophy alongside running the business.

EPC Register

Accredited assessor

MSc

Built environment

MSc Philosophy

Currently studying

10+ years

London property

Part L focus

Design to as-built

Off the clock: cricket, family time, an MSc in philosophy in progress and finding London's best food.

Awais Sarwar

Founder · Accredited energy assessor

About Awais