As built Part L evidence to discharge an energy condition

A planning energy condition usually says something like this: prior to first occupation, evidence shall be submitted demonstrating that the development has been constructed in accordance with the approved energy statement and achieves the carbon reduction stated in it. The evidence that discharges it is the as-built Part L calculation, the air permeability test certificate for each dwelling, the Building Regulations England Part L report in its as-built form, and the photographic evidence that Approved Document L has required since the 2021 edition.

None of that can be produced before the building is finished. So the paperwork has to be collected as the house goes up, and the discharge application has to be allowed for in the programme ahead of the date you want to move in.

What the condition usually asks for

Read the condition carefully, because the wording decides what you have to produce. Four forms are common.

The first asks for evidence of compliance with the approved Energy Statement, which means showing the as-built performance against the figures in that document, not against the Building Regulations target.

The second asks for a post-construction report showing the carbon reduction achieved against a stated percentage. Here the comparison is a calculation, and the baseline used in the original statement has to be reproduced.

The third asks for evidence that specified measures have been installed, such as a heat pump of a stated output, a photovoltaic array of a stated capacity, or mechanical ventilation with heat recovery. That is the easiest to satisfy: commissioning certificates and photographs.

The fourth, which appears in London and in a growing number of other authorities, requires reporting of actual metered energy use for a period after occupation. That is a different obligation entirely and needs metering designed in from the start.

Where the condition is ambiguous, write to the authority early and ask what evidence will be accepted. A short email answered at foundation stage saves a dispute at completion.

As designed against as built calculations

Part L 2021 requires two calculations for a new dwelling. The as-designed calculation is produced before work starts and generates the design stage Part L report. The as-built calculation is produced at completion and generates the as-built report.

The two differ for perfectly ordinary reasons. A window supplier substitutes a different unit, the heat pump installed is a different model from the one specified, the air test result comes in better or worse than the design figure, a thermal bridging detail is built differently, or the orientation of a plot is mirrored on a repeat house type.

Keep a change log. Every substitution that affects the calculation should be recorded with the date, the reason and the replacement specification, so that the as-built calculation can be explained rather than defended.

Air permeability test results

Testing is the item most likely to disrupt the programme, because it happens late, it needs the building substantially complete and sealed, and a failure means remedial work followed by a retest.

The practical points for a self-build or a small site:

1. Book the test with a suitably accredited tester well in advance; availability tightens at the end of a quarter.
2. The building needs all penetrations sealed, trickle vents closable, and the ventilation system installed, so schedule it after first fix and after the extract terminations are finished.
3. If the design figure is tight, carry out an early indicative test at airtightness layer stage, when faults can still be reached. The cost of an early test is small against the cost of chasing leaks through finished plasterboard.
4. The certificate has to identify the dwelling, the measured result, the test standard and the tester's accreditation.
5. A result worse than the design figure requires the as-built calculation to be rerun, and that may put the dwelling below the approved performance.

The common leakage paths on a small site are the junction between the airtightness layer and the window frame, service penetrations through the ceiling into the loft, the loft hatch, soil vent pipe penetrations, and the gap behind the plasterboard at the floor perimeter. Where the external terminations for ventilation have been cut in late, they are a frequent culprit, which is one reason to settle the external terminations for heat recovery ventilation at design stage.

Photographic evidence requirements

The 2021 edition of Approved Document L introduced a requirement for photographic evidence of specified construction stages, provided with the Part L report. This is the requirement self-builders most often discover too late, because the photographs have to be taken as the work proceeds and cannot be recreated afterwards.

Take geo-located and time-stamped photographs of:

• foundation and ground floor insulation, including edge insulation and the continuity at the perimeter
• wall insulation at each storey, showing continuity at junctions and around openings
• the airtightness layer, with laps, tapes and penetrations visible
• window and door installation, showing the seal between frame and airtightness layer
• roof and loft insulation, including at the eaves and around the loft hatch
• services penetrations and their sealing
• the heating appliance, cylinder, ventilation unit and any photovoltaic installation, with nameplates legible

Name the files by plot, element and date and store them in a single folder from day one. A bricklayer will not go back and take the photograph, and an assessor cannot sign a report without it.

Handling a shortfall against the approved figures

Sometimes the as-built numbers fall short of what the planning condition requires. That is recoverable, but it has to be handled openly.

The options, roughly in order of preference:

Remedial work comes first where it is practical. Adding loft insulation, sealing leakage paths and retesting, or adding photovoltaic capacity are all straightforward on a small site and will usually close a modest gap.

Recalculation comes second. Where the original statement used conservative assumptions, rerunning the calculation with as-built data sometimes improves the result. Check whether accredited construction details were actually built, because switching from default to accredited psi values can be worth more than it sounds.

Negotiation comes third. Submit the discharge application with the as-built evidence, the explanation of the shortfall, and a proposal: additional measures, a commuted contribution where the authority has a published mechanism, or an agreed variation. The Sustainability Statement or energy statement that was approved is the benchmark, so quote its figures and show the difference precisely.

What does not work is submitting the evidence without comment and hoping the gap is not noticed. Energy conditions are checked by officers who read the numbers, and a refused discharge application leaves you occupying in breach.

Timing against first occupancy

The sequence that causes trouble is this: completion, move in, then discover the condition said prior to first occupation.

Work backwards from the occupation date instead:

1. Airtightness test and remedial work, allowing two weeks for a retest if needed.
2. Commissioning of the heating, ventilation and renewable systems, with certificates.
3. As-built calculation and Part L report, typically one to two weeks with the assessor.
4. Energy Performance Certificate lodged.
5. Discharge of conditions application submitted, with the statutory period of eight weeks for a decision.

That is comfortably three months from a sealed building to a discharged condition. Councils will often accept an application for discharge submitted before occupation and determined afterwards, but the condition as written may not permit it, so ask rather than assume. Where the electrical supply or the heat source has changed during construction, the point about peak electrical demand and all-electric heating is worth revisiting, because a substituted system changes the calculation as well as the connection.

Keeping the paperwork from the start

A single folder, set up before the first delivery, holds everything the discharge will need.

Put in it the approved energy statement and the planning decision notice with the condition wording, the design stage Part L report and calculation, product datasheets and certificates for every specified item as it is ordered, the photographic record organised by element, the change log, the air test certificates, commissioning certificates for every system, and the as-built report when it arrives.

Give one person responsibility for it. On a self-build that is usually you, and the discipline is the same as keeping receipts: tedious at the time, and the only thing that works at the end.

Enter your postcode on PlanScope to see which reports and conditions a new dwelling at your site is likely to involve.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Part L calculations and air permeability testing must be carried out by suitably accredited persons. This article is general guidance rather than legal advice.