Energy assessor roles: who produces which calculation
The person who runs the compliance calculation and the person who designs the energy strategy are usually different people, and planning conditions are often drafted as though they were one.
The person who runs the compliance calculation and the person who designs the energy strategy are usually two different people, and planning conditions are routinely drafted as though they were one. That causes two failures. A design team appoints an accredited assessor and expects a strategy. Or it appoints a building services engineer and discovers at discharge of conditions that nobody holds the accreditation needed to lodge the output.
Sorting out who does what is straightforward once the calculations are separated from the design, because the accreditation routes follow the calculation, not the building.
The calculations a planning energy statement relies on
An Energy Statement submitted with a planning application normally rests on three or four distinct pieces of analysis, and each has a different author.
The regulated energy and carbon calculation, which demonstrates performance against the Building Regulations target and, where a local policy sets a percentage improvement, against that policy. This is a compliance calculation run in approved software by an accredited assessor.
The energy strategy, which selects the fabric performance, the heating and hot water system, the ventilation approach and any renewable generation, and sequences them. This is design work by a building services engineer or an architect working with one.
The overheating analysis, which under the current regime is either a simplified method or a dynamic thermal model. Dynamic modelling to the CIBSE methodology is specialist work and usually sits with the engineer or a dedicated modeller rather than with the compliance assessor.
And, on larger or London schemes, a whole life carbon assessment and a monitoring commitment, each with their own methodology and author.
An energy statement that presents all four as a single document by a single author is common, and the question to ask is which parts of it that author is accredited to produce.
Domestic and non-domestic methodologies
The split is procedural rather than physical, and it follows the building type.
Dwellings are assessed using the national calculation methodology for homes, run in approved software, producing a target and an actual emission rate together with fabric and primary energy metrics. The output is the compliance report and, at completion, the energy performance certificate.
Other buildings are assessed using the simplified building energy model for most cases, or an approved dynamic simulation model where the building's form, servicing or glazing makes the simplified route unsuitable. The output is the compliance report for the building, plus the certificate at completion.
Mixed-use buildings need both, and that is where coordination errors appear. A block with flats over a commercial ground floor needs the dwellings assessed under the domestic methodology and the commercial space under the non-domestic one, with the shared systems apportioned consistently between them. Communal heating serving both is the recurring problem, because the way losses and generation are attributed differs between the two methodologies and an inconsistency is visible to anyone who adds the numbers up.
Accreditation schemes and what they cover
Accreditation is held by individuals, through schemes approved for the purpose, and it is specific to the calculation type and level.
| Calculation | Who is accredited to produce it |
|---|---|
| New dwellings compliance calculation and predicted certificate | An on-construction domestic energy assessor |
| Existing dwellings certificate | A domestic energy assessor |
| Non-domestic simplified model for new buildings | A non-domestic energy assessor at the level covering new-build simplified modelling |
| Non-domestic dynamic simulation model | A non-domestic energy assessor at the higher level covering dynamic simulation |
| Existing non-domestic certificate | A non-domestic energy assessor at the level matching the building's complexity |
Two consequences for appointments. An assessor accredited for existing dwellings cannot lodge a new-build calculation, which surprises clients who have used the same person for an existing portfolio. And an assessor accredited for simplified non-domestic modelling cannot lodge a dynamic simulation output, so a building that turns out to need dynamic modelling needs a different assessor, not a different piece of software.
Ask for the accreditation scheme, the level and the individual's registration number at appointment, and ask specifically whether they are accredited for the calculation your building needs.
Design stage against as-built calculations
Two calculations are required and they are not the same exercise.
The design stage calculation is run on the specification and the drawings. It is the one quoted in the planning energy statement, the one used to discharge a planning condition requiring a percentage improvement, and the one that goes to building control before work starts.
The as-built calculation is run on what was actually constructed, with the installed products, the measured air permeability, the commissioning data and any substitutions. It produces the certificate that is lodged.
The gap between the two is where projects lose compliance. A substituted boiler or heat pump, a glazing unit with a different g-value, a change of insulation product, an air test result worse than the design assumption, or a photovoltaic array reduced in size will all move the as-built figure. Where the planning condition requires a stated improvement to be achieved rather than designed, that gap is a planning breach as well as a building regulations problem.
The control is unglamorous and effective: lock the specification items that the calculation depends on, require the assessor to re-run on any substitution before it is ordered, and keep the air permeability target as a contractual obligation rather than an aspiration.
Where a building services engineer is needed instead
The accredited assessor runs software against inputs. They are not, by virtue of accreditation, qualified to design the system that produces those inputs.
Design work that needs an engineer includes sizing heat emitters and the heat pump for the actual flow temperature, designing the distribution and the hydraulics, specifying and designing ventilation to the relevant approved document, designing the overheating mitigation rather than only testing it, specifying controls and metering, and producing the commissioning strategy.
The division that works in practice is that the engineer owns the strategy and the specification, the assessor owns the calculation and the lodgement, and the two exchange information at defined points. Where one person does both, they should be able to say which hat they are wearing for each output.
On low-rise housing this distinction is often blurred because a competent assessor with design experience can handle a simple gas-free dwelling end to end. On a mixed-use block with communal heat, mechanical ventilation with heat recovery and a part-glazed commercial unit, blurring it produces a calculation nobody can defend.
The professional directory is the route for a reviewer to check an energy statement before submission, and the report index shows how the energy document relates to the overheating, sustainability and carbon reports.
London energy reporting requirements
London schemes carry a separate layer, and the requirements are policy rather than regulation.
Energy assessments for referable and major schemes follow the Greater London Authority's energy assessment guidance, structured around the "Be Lean, Be Clean, Be Green, Be Seen" hierarchy, with carbon reductions reported at each stage against a baseline and a shortfall against the net zero target met through a carbon offset payment calculated under the published methodology.
Three practical points. The reporting template and the baseline definitions are prescribed, so the assessment has to be produced in the required format rather than translated into it afterwards. The "Be Seen" stage imposes a post-construction monitoring and reporting obligation, usually secured by condition or obligation, which means someone has to be appointed to collect and submit in-use data after completion. And whole life carbon assessment for referable schemes follows the RICS methodology and is a separate specialism from the operational energy calculation.
Budget for the offset payment early. It is a function of the residual regulated carbon over a 30-year period at the published rate per tonne, so a strategy that falls short on site carries a cost that appears at the section 106 stage rather than in the construction budget.
Commissioning in the right order
The sequence that avoids rework:
- Appoint the building services engineer at concept to set the strategy and the fabric targets.
- Appoint the accredited assessor for the correct calculation type as soon as the strategy is outlined, so the first compliance run informs the design rather than reporting it.
- Run the overheating analysis before the glazing and the ventilation strategy are fixed, because the mitigation options narrow once they are.
- Produce the energy statement for planning from the design stage calculation, with the methodology, software version and assumptions stated.
- Lock the calculation-critical specification items into the contract.
- Re-run on every substitution, before procurement.
- Run the as-built calculation on measured data and lodge the certificate.
One honest uncertainty worth flagging to clients: the domestic compliance methodology and the standard it implements are under reform, with the Future Homes Standard announced and the calculation tool for dwellings expected to change with it. Transitional arrangements matter for schemes with permission now and construction later, so check the current position and the transitional provisions on gov.uk before quoting a percentage improvement in a planning document that may be discharged years later.
Where overheating is likely to be the binding constraint, the separate Overheating Risk Assessment should be commissioned alongside the energy work rather than after it. Comparable competence questions for other specialist authors are set out in acoustician qualifications in planning and hydrologist or drainage engineer for a drainage strategy.
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.
Frequently asked questions
Can one person produce the whole energy statement?
Sometimes, on a simple low-rise dwelling. On a mixed-use block with communal heat and mechanical ventilation, the compliance calculation, the strategy design, the overheating analysis and any whole life carbon work are separate specialisms. Ask which parts the author is accredited to produce and which parts are design rather than calculation.
Which accreditation is needed for a new-build dwelling calculation?
An on-construction domestic energy assessor accreditation. Someone accredited only for existing dwellings cannot lodge a new-build calculation, which catches clients who have used the same assessor across an existing portfolio. Ask for the scheme, the level and the registration number, and confirm it covers the calculation your building needs.
When does a non-domestic building need dynamic simulation?
Where the building's form, servicing or glazing makes the simplified model unsuitable. Dynamic simulation requires a non-domestic energy assessor accredited at the higher level, so a building that turns out to need it needs a different assessor rather than different software. Establish which route applies before appointing.
Why does the as-built calculation often fail the planning condition?
Because substitutions move the result. A different heat pump, glazing with another g-value, a changed insulation product, an air permeability result worse than assumed, or a reduced photovoltaic array all shift the figure. Where the condition requires an improvement to be achieved rather than designed, the gap is a planning breach as well.
What extra steps apply to London schemes?
Energy assessments for referable and major schemes follow the Greater London Authority guidance and the Be Lean, Be Clean, Be Green, Be Seen hierarchy, reported in the prescribed format with any shortfall met by a carbon offset payment. The Be Seen stage adds post-construction monitoring and reporting, which needs someone appointed to deliver it.
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.