How the Part L 2021 uplift changed planning energy statements

The 2021 edition of Approved Document L changed the arithmetic behind every planning energy statement in England, and a percentage improvement quoted without a stated baseline is now close to meaningless. A scheme claiming a 35 per cent improvement over Building Regulations could be measuring against the 2013 standard, the 2021 standard, or a notional building the author has misdescribed. Those are three different claims, and only one of them answers the policy.

State the edition, the SAP version and the notional specification on the first page. Everything else in the statement depends on it.

What the 2021 uplift actually changed

Three changes matter for planning.

The target tightened. The notional dwelling specification was revised so that a compliant new home produces in the order of 31 per cent less carbon than one built to the 2013 standard, with a smaller uplift for non-domestic buildings.

A primary energy target appeared alongside the carbon target. A dwelling is now assessed against a Target Emission Rate for carbon, a Target Primary Energy Rate measured in kWh per square metre per year, and a Target Fabric Energy Efficiency rate. All three must be met.

And the calculation method moved to SAP 10, which changed the carbon factors underneath everything.

Transitional arrangements applied to work already in the system, so buildings are still being completed to the 2013 standard on permissions granted years ago. That is one reason confusion persists on live projects.

Why the baseline has to be named

A percentage improvement is a comparison, and comparisons need two terms. The problem is that local plan policies written before 2021 usually name only one.

A policy requiring a 20 per cent improvement over Part L was drafted against the 2013 notional building. Applied against the 2021 notional building it asks for something considerably harder, because roughly 31 per cent of the available saving has already been taken by the regulations themselves. Applied against the 2013 baseline in 2026, it asks for something a compliant scheme already exceeds.

Neither reading is obviously right, and officers vary. What works is transparency. Show the Dwelling Emission Rate against the 2021 Target Emission Rate, state the resulting improvement, and then state separately what the same scheme achieves against the 2013 notional building if the policy assumed it. Two numbers, both labelled, with the policy quoted. The Energy Statement is the right place for that reconciliation, and it removes an argument that otherwise runs through the whole determination.

Carbon factors and what they did to heat pumps

The electricity carbon factor in SAP 10 is roughly a quarter of the figure used in SAP 2012, reflecting the decarbonisation of grid supply. That single change reordered the technologies.

Under SAP 2012, electric heating scored badly on carbon and gas scored well. Under SAP 10, an air source heat pump running at a seasonal performance factor of three or better produces very low modelled emissions, and a gas boiler no longer has an arithmetic advantage. Photovoltaic panels, meanwhile, save less modelled carbon per kWp than they used to, because the electricity they displace is cleaner.

The practical consequence for an energy statement is that the low carbon strategy and the renewable generation strategy have separated. Meeting a carbon target through a heat pump is straightforward. Meeting a policy that specifically requires a proportion of energy from on-site renewable generation still needs an array, and the two requirements are not interchangeable.

Primary energy is the target people fail

Primary energy accounts for the energy used to generate and deliver the fuel, rather than the carbon it emits at the meter. The primary energy factor for grid electricity is well above one, so electrical heating carries a penalty on this metric that it does not carry on carbon.

A heat pump with a good coefficient of performance passes comfortably. Direct electric panel heaters, immersion-only hot water, or a heat pump modelled with radiators sized for high flow temperatures can fail the Target Primary Energy Rate while passing the carbon target.

I have seen more than one scheme approved at planning on a carbon-only energy statement and then redesigned at Building Control because primary energy did not work. Report all three rates in the statement. It costs a table and it prevents that.

Restating older policy targets

Where the adopted plan predates the uplift, take this approach in the statement.

1. Quote the policy in full, including the baseline it names.
2. Identify the edition of Approved Document L that was in force when the policy was adopted.
3. Report the scheme against the current targets: Dwelling Emission Rate, Dwelling Primary Energy Rate and fabric energy efficiency, each against its target.
4. Report the improvement against the current baseline as the headline figure.
5. Report the equivalent against the older baseline in a clearly labelled secondary row, for the officer's comparison.
6. Say which reading you consider correct and why, in two sentences.

Do not pick whichever comparison flatters the scheme and present it alone. Officers who have seen the trick once look for it every time afterwards.

Where officers challenge the numbers

Four challenges recur.

Claiming credit for measures already in the notional building. The 2021 notional specification includes waste water heat recovery and photovoltaics for a typical house type, so specifying them is not automatically an improvement over the target. Say what the notional building contains before claiming a saving against it.

Modelling assumptions that the drawings do not support. A thermal bridging psi value taken from an accredited detail requires that detail to be built, and an officer or Building Control inspector can ask for the construction drawing.

Air permeability targets that the contractor has not seen. A design assuming three cubic metres per hour per square metre at 50 pascals on a masonry cavity build is achievable and needs to be specified, tested and budgeted.

Overheating treated as a separate universe. The measures that improve the energy result, particularly large south-facing glazing for solar gain, work against Approved Document O. Run the Overheating Risk Assessment with the same model assumptions and reconcile them before submission.

What to put in the statement now

For a residential scheme, a usable energy statement covers the policy and its baseline, the three target and actual rates, the notional and as-designed specification side by side, the energy hierarchy applied in order, the heating and hot water strategy with assumed flow temperatures, any generation with array size and orientation, and the overheating position. Where the local plan asks for wider sustainability commitments, a Sustainability Statement carries those, and in London or on larger schemes a Whole Life Carbon Assessment sits alongside.

Illustrative example: a 14-unit scheme where the adopted policy asks for a 19 per cent improvement over Part L. The statement reports a Dwelling Emission Rate 24 per cent below the 2021 Target Emission Rate, notes that the same design sits around 48 per cent below the 2013 target, quotes the policy, and states that the 2021 comparison is the meaningful one because the regulations have already delivered part of the saving the policy sought. The officer accepted the reasoning in a paragraph.

PlanScope drafts energy statements structured to the policy being answered and flags the figures it cannot verify rather than inventing them. See PlanScope pricing for what a draft costs.

This is general guidance, not legal advice; check the position with your local planning authority, Building Control 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.