Part L 2021 and what an energy statement must now show
Primary energy joined emissions as a headline metric, the grid carbon factor fell sharply, and fabric targets now constrain design early. Here is what an energy statement has to demonstrate.
The 2021 edition of Approved Document L changed the arithmetic of new housing more than any building regulations uplift in a decade, and it changed what a planning energy statement has to demonstrate. New dwellings are now tested against three targets rather than one, primary energy joined carbon emissions as a headline metric, and the carbon factors behind the calculation moved far enough to reverse the ranking of heating systems.
If you are still producing energy statements built around a percentage improvement over the 2013 standard, the numbers in them no longer mean what the policy assumed they meant.
What the 2021 uplift changed for new dwellings
The 2021 edition applied in England from 15 June 2022, with transitional arrangements for schemes where a building notice or full plans application had been made before that date and work started within the following twelve months. Those transitional provisions have largely run out now, so on most live sites the 2021 standard applies.
Government presented the uplift as an interim step ahead of the Future Homes Standard, delivering around a 31 per cent reduction in carbon emissions for new dwellings against the previous edition. The Future Homes Standard itself has been the subject of consultation and repeated timetable changes, so treat any date for it as provisional and check the current position rather than designing to a standard that has not been published. It is a fabric and services uplift rather than a change of approach: better insulation and airtightness, improved services efficiency, lower distribution temperatures for wet heating systems, and tighter control of thermal bridging.
Three practical additions matter for design teams. Low temperature heating design, with a flow temperature at or below 55 degrees, is now the expectation for wet systems in new dwellings. Photographic evidence of insulation and airtightness detailing is required as part of the compliance report. And as-built calculations are checked against the design ones rather than assumed to match.
Primary energy, emissions and fabric targets
New dwellings are assessed against three limits, and passing two of them is not compliance.
| Target | Measures | Unit |
|---|---|---|
| Target primary energy rate | Primary energy demand including generation and distribution losses | kWh per m2 per year |
| Target emission rate | Carbon dioxide emissions | kg CO2 per m2 per year |
| Target fabric energy efficiency | Space heating and cooling demand from the fabric alone | kWh per m2 per year |
The fabric target is the one that constrains design earliest, because it is unaffected by the heating system. You cannot fix a poor fabric result with a better boiler or with photovoltaics.
Primary energy is the metric most teams find unfamiliar. It weights delivered energy by the energy used to produce and deliver it, which penalises electric direct heating and rewards heat pumps for the same delivered heat.
It also changes how photovoltaics behave in the calculation. Generation offsets primary energy demand, so an array helps with two of the three targets and does nothing at all for the third. Teams that add panels late to rescue a failing result often find the fabric figure unchanged.
Carbon factors and the effect on heating choices
This is where the uplift bites hardest on design decisions. The carbon factors used in the compliance calculation were updated, and the grid electricity factor fell sharply, to 0.136 kg CO2 per kWh in SAP 10.2 against 0.519 in the earlier methodology.
Mains gas did not move in the same way. So a heat pump that once looked worse than a gas boiler on the emissions metric now looks considerably better, and a scheme designed around gas has to work much harder to hit the target emission rate.
The consequence for planning is that an energy statement written against the old factors reaches conclusions that are now wrong rather than merely out of date. Check the version of the calculation methodology behind any figure you are quoting, and say which version it is.
Where planning policy asks for more than the regulations
Local plan energy policies and the Building Regulations are different instruments with different enforcement routes, and the relationship between them has been contested for years.
Some adopted local plans require a percentage improvement over the regulations, a fabric energy efficiency standard, or on-site renewable generation. In London, the energy hierarchy of be lean, be clean, be green and be seen applies through the London Plan, with a carbon offset payment where on-site zero carbon is not achieved and a monitoring requirement after occupation.
Government has issued written ministerial statements on the extent to which local planning authorities should set energy efficiency standards beyond the Building Regulations, most recently in December 2023, and the position continues to be argued over in local plan examinations. Check the current statement and the wording of the adopted policy for the authority you are submitting to, rather than assuming either that local standards apply or that they do not. The planning law timeline is the place to follow how this develops.
What the energy statement should contain
An Energy Statement for a residential scheme in England should work through the following, in this order.
- The policy requirements that apply, quoted from the adopted local plan and any supplementary document, with the national position stated.
- The baseline: the notional building and the targets it generates for this scheme.
- Demand reduction through fabric, with U-values, airtightness, thermal bridging approach and the fabric energy efficiency result.
- Efficient supply: the heating and hot water strategy, distribution temperatures, controls and ventilation.
- Renewable generation, with the area, orientation and yield assumptions stated.
- The resulting primary energy, emissions and fabric figures against each target, presented as a table.
- Any shortfall and how it is addressed, including offset payments where the policy provides for them.
- Overheating, cross-referred rather than repeated.
Overheating deserves its own document on anything of scale. Part O introduced a separate assessment route, and an Overheating Risk Assessment using the dynamic modelling method gives a more defensible answer than the simplified method on flats with restricted openings.
Where the local plan asks for broader sustainability commitments, water use, materials, waste and biodiversity, those belong in a Sustainability Statement rather than being bolted onto the energy calculations.
Common gaps officers pick up
The recurring ones are easy to avoid and cost weeks when missed.
- Figures quoted against the wrong edition of the regulations or the wrong calculation methodology version
- A percentage improvement stated without saying what the baseline is
- Photovoltaic areas that do not fit on the roofs shown on the submitted drawings, or that sit on north-facing slopes
- Heat pump plant with no space shown for it, no acoustic assessment and no allowance for external unit siting
- An energy strategy that contradicts the overheating assessment, typically by assuming windows open that the overheating work assumes are shut
- No statement of who carried out the calculations or which software was used
That last point is worth taking seriously. Where a scheme relies on a rooftop array to meet a target, the array has to appear on the planning drawings, and our note on solar panels and permitted development limits covers where separate consent is needed for later additions.
This is general guidance, not legal advice. Check the current Approved Document, the calculation methodology version and your authority's adopted policy before relying on any figure here.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
When did Part L 2021 take effect?
The 2021 edition applied in England from 15 June 2022, with transitional arrangements where a building notice or full plans application had been submitted before that date and work started within the following twelve months. Those transitional provisions have largely expired, so the 2021 standard applies on most live sites.
What are the three targets for new dwellings?
The target primary energy rate, measuring primary energy demand including generation and distribution losses; the target emission rate, measuring carbon dioxide; and the target fabric energy efficiency rate, measuring space heating and cooling demand from the fabric alone. A scheme has to meet all three, and the fabric target cannot be offset by better services.
Why do heat pumps now perform better in the calculation?
Because the carbon factor for grid electricity fell to 0.136 kg CO2 per kWh in the updated methodology, against 0.519 previously, while the factor for mains gas did not move comparably. The same delivered heat from a heat pump therefore scores far better on the emission rate than it did under the older factors.
Can a local plan require better than Part L?
Some adopted plans do, through percentage improvements, fabric standards or on-site renewable requirements, and the London Plan operates an energy hierarchy with carbon offset payments. Government has issued written ministerial statements on how far authorities should go, most recently in December 2023, so check the current statement and the adopted wording.
Does the energy statement cover overheating?
It should cross-refer rather than duplicate. Part O introduced a separate assessment with a simplified and a dynamic modelling route. On flats with restricted opening windows the dynamic method usually gives a more defensible answer, and the two documents must share the same assumptions about whether windows are open.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.