Energy and carbon evidence by scheme size

There is no national energy statement threshold. What exists is a set of local validation requirements that mostly bite at major development, meaning ten or more dwellings or 1,000 m² of floorspace, plus a separate set of policy expectations that scale up again on larger schemes and in London. Below major, most councils ask for nothing beyond a note; above it, the energy statement becomes a document the case officer will read against policy.

That gap between building control and planning is where architects lose time. Part L is tested at building control, after permission. The energy statement is tested at planning, before it. They use the same modelling and answer different questions, and submitting one where the other is wanted is a common validation query.

What national building standards already require

The 2021 edition of Approved Document L sets the baseline for new dwellings: a primary energy target, a target emission rate and a fabric energy efficiency target, with the 2021 uplift requiring around a 31 per cent reduction in carbon emissions against the previous edition. Part O sets an overheating requirement for new residential buildings, assessed either by the simplified method or by dynamic thermal modelling. Part F covers ventilation, and the three have to be designed together because a fabric first approach without ventilation design produces an overheating failure.

Two things follow for planning.

You do not need to prove Part L compliance to get planning permission. Building control does that, and a planning condition requiring Part L compliance is unnecessary because the Regulations already apply.

But you do need your planning drawings to be capable of delivering what your energy strategy assumes. Plant space, riser sizes, photovoltaic array area, heat pump locations, external unit acoustic separation and flue positions all appear on planning drawings or they appear later as a non material amendment.

The Future Homes Standard has been signalled for some time as the next step, with much deeper carbon reductions and a zero carbon ready specification. As at September 2026 the in force date and the transitional arrangements are the thing to verify rather than assume, because designing to a standard that is not yet in force is a commercial decision and designing to one that has just come into force is a compliance requirement.

Where local plan policies go further

Section 1 of the Planning and Energy Act 2008 lets local plans include policies imposing reasonable requirements for energy efficiency standards that exceed the building regulations. That power is the basis of most local carbon policies.

It has been contested territory. Written ministerial statements have at various points discouraged authorities from setting their own standards above the national ones, and the position has shifted more than once, so read both the adopted local plan policy and any more recent national statement before advising a client that a local standard applies. Where a policy is in an adopted plan, it is part of the development plan and section 38(6) of the Planning and Compulsory Purchase Act 2004 applies.

The policies you will actually meet, in rough order of frequency:

• A percentage carbon reduction beyond the current Part L baseline, evidenced by modelling.
• A requirement to follow an energy hierarchy and to demonstrate each step.
• A water efficiency standard, usually the optional 110 litres per person per day figure.
• An overheating assessment requirement for flats and single aspect units.
• A renewable energy contribution expressed as a percentage of demand or as installed capacity.
• In London, net zero carbon for major development with a minimum on site reduction and a cash offset for the remainder.

Thresholds that trigger an energy statement

The pattern across authorities is consistent enough to plan around, even though the detail varies.

Two dwellings is the scale at which people first get caught out, because the jump from one house to two changes several requirements at once, as our note on what changes from a single house to two dwellings on one plot sets out.

The document to check is the authority's local validation list, not the national list. An Energy Statement appears on many of them at the major threshold, and a Sustainability Statement sometimes appears at a lower one, covering water, materials, waste and biodiversity alongside energy.

The energy hierarchy and how it is evidenced

The hierarchy most policies use runs be lean, be clean, be green, and on larger schemes be seen. Officers want the numbers at each stage. The narrative around them matters much less.

A usable energy statement shows:

1. The baseline: regulated carbon emissions for the scheme built to the current Part L compliant specification, from the modelling software, stated per dwelling and in total.
2. Be lean: the reduction achieved by fabric and passive measures alone, with the U values, air permeability and thermal bridging assumptions listed.
3. Be clean: whether a heat network exists or is planned within a reasonable distance, and the outcome of that assessment even where the answer is no.
4. Be green: the reduction achieved by low carbon and renewable technologies, with the array area or capacity that the drawings can actually accommodate.
5. The residual emissions, and how any policy shortfall is dealt with.

The commonest failure is an array area that does not exist. A statement claiming a 45 kilowatt peak roof mounted array on a roof that also carries plant, rooflights and a communal terrace will be checked against the roof plan, and the mismatch undermines everything else in the document.

Overheating sits alongside this. Where the local plan or the unit mix makes it a live issue, an Overheating Risk Assessment using dynamic modelling to the relevant CIBSE method gives a defensible answer, and it will often change the glazing specification and the ventilation strategy in ways that feed back into the energy figures. Run the two together rather than sequentially.

Whole life carbon expectations on larger schemes

Whole life carbon is embodied plus operational carbon across the building's life, assessed in modules covering product and construction, use, and end of life.

Where it is required, which in practice means London referable schemes and a growing number of authorities elsewhere, a Whole Life Carbon Assessment prepared to the RICS methodology is the expected form. The assessment reports carbon per square metre of gross internal area, compares against benchmarks, and identifies the reductions achieved through design choices.

The design decisions it exposes are structural and early: frame material, substructure extent, basement provision, façade specification and the proportion of existing structure retained. Which means a whole life carbon assessment commissioned after planning submission cannot influence anything. It becomes a reporting exercise, and reviewers can tell.

Retention is the strongest lever. Keeping a frame or a substructure avoids a large share of the embodied carbon in a new build, and on refurbishment schemes it is usually the argument that carries the assessment.

Offsetting contributions and their basis

Where a policy requires net zero carbon and the scheme cannot achieve it on site, the shortfall is typically paid as a carbon offset contribution: residual regulated emissions multiplied by a price per tonne, multiplied by a period, commonly 30 years, and secured through a planning obligation.

Three points worth knowing before you advise on the figure.

The price per tonne is set locally and is revised, so quote the mechanism and point to the current published figure rather than repeating a number from an old report.

The contribution is calculated on residual regulated emissions, so improvements at the lean and green stages reduce it directly. That makes the trade between capital cost and offset payment a real design conversation rather than an afterthought.

And the obligation has to be justified against the tests in regulation 122 of the Community Infrastructure Levy Regulations 2010, which occasionally gives grounds to question a mechanically applied figure.

Coordinating the evidence with the design team

The failure mode here is procedural rather than technical. The energy statement is written by one consultant, the drawings by another, and nobody checks them against each other before submission.

A short coordination routine that prevents most of it:

• Fix the energy strategy before the planning drawings are finalised, not after.
• Put the photovoltaic array on the roof plan at the area the statement claims, with plant and access space shown around it.
• Show plant rooms, risers, external heat pump units and flue terminations on the submitted drawings.
• Check that the overheating strategy's openable areas match the elevations and the acoustic assessment.
• Have one person read the energy statement and the drawings side by side, looking only for contradictions.

That last step takes an hour and catches most of what officers raise.

This is general guidance, not legal advice. Local energy policies, validation lists and offset prices vary by authority and are revised, so check the current position with your local planning authority or a qualified professional before relying on it.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.