The four stages of an Energy Statement

An Energy Statement built on the be lean, be clean, be green hierarchy reports the same scheme four times, and each report has to reconcile with the last. The structure comes from the London Plan and has been adopted in similar form by authorities well outside London: reduce demand through fabric and form, then supply the remaining demand efficiently, then meet what is left from renewables, then measure and report what the building actually does. The fourth stage, be seen, is the one most often missing from a submission.

What the officer is checking is arithmetic continuity. Four emissions figures, each derived from the last, with the percentage saving at each step and a residual figure at the end. A statement that presents a good final number without showing the intermediate steps will be sent back.

The hierarchy and what each stage covers

The four stages are sequential, and the sequence is the policy. You cannot buy your way past poor fabric with photovoltaic panels, because the be lean saving is assessed on its own before anything else is counted.

The baseline is a building regulations compliant version of the same scheme, so every saving is expressed against a notional building rather than against an absolute target. That matters when the regulations change, because a percentage saving against an older baseline is not comparable with the same percentage against a newer one. State which edition of Approved Document L the baseline was modelled to.

London Plan policy expects major development to be net zero carbon with a stated minimum reduction achieved on site, including a minimum from energy efficiency alone. Those figures have been revised as the building regulations baseline moved, so check the current Greater London Authority guidance rather than quoting a number from an older statement.

Fabric measures and the be lean baseline

Be lean is where the design either works or does not, and it is the stage that cannot be retrofitted later.

The measures that move the figure are unglamorous: compact form with a low heat loss perimeter, glazing ratios set by elevation, airtightness better than the limiting standard, continuity of insulation at junctions, efficient mechanical ventilation with heat recovery, and lighting and controls specified rather than assumed.

Two habits weaken this section. The first is quoting element U-values without stating the resulting heat loss parameter, which is the number the model actually uses. The second is claiming an airtightness figure the construction type cannot deliver, which shows up at the as-built test and leaves the client with a compliance problem and a condition to discharge.

Set out the fabric specification in a table and commit to it, because the approved drawings and conditions will refer back to this section. The discipline is the same one described in our note on the baseline chapter of an environmental statement: if the baseline is not transparent, nothing derived from it can be checked.

Heat networks and the be clean stage

Be clean asks how the remaining demand is supplied. The expected order is connection to an existing heat network where one is available, then a site wide communal system designed for future connection, then individual systems within each unit.

So the first item in this section is evidence of the enquiry. Name the network operator contacted, the date, and the answer. Where no network exists or connection is not feasible, say so with the evidence rather than asserting it, because an officer who knows a network is being built nearby will ask.

The arithmetic here has changed considerably as grid electricity has decarbonised. Gas fired combined heat and power, which used to generate most of the be clean saving, now often produces very little and creates an air quality problem at the same time. Heat pumps have moved into this part of the assessment, and the current guidance determines whether their contribution is reported at the be clean or the be green stage, so confirm the treatment before modelling.

Where a communal system is proposed, the metering and distribution design belongs in the strategy, along with the space and route safeguarding for a future connection.

Renewables and the be green stage

Be green covers on-site renewable generation. In practice that means photovoltaic panels on most schemes, with solar thermal where the hot water demand profile suits it and other technologies where the site allows.

Three points recur in officer comments.

Roof area is finite and contested. Photovoltaic panels, plant, green roof, amenity space and access all want the same surface, so the roof plan should show the allocation rather than stating a peak capacity figure with no layout.

Yield assumptions need stating: orientation, tilt, shading from plant and parapets, and the assumed performance factor. A capacity in kilowatts peak tells the officer nothing about the emissions saving claimed.

And the panels have to be secured. If the be green saving depends on the array, the array belongs on the approved drawings and in a condition, or it will be the first thing removed when the contract sum is reviewed.

Monitoring and the be seen stage

Be seen is the reporting stage, and it is a commitment rather than a calculation. Where the policy applies, the applicant agrees to report predicted performance at planning stage, as-built performance on completion, and measured in-use performance for a period after occupation, through the reporting route the authority specifies.

That requires metering granular enough to separate regulated from unregulated energy and to isolate each low carbon technology, a named party responsible for collecting and submitting the data, and a route that does not depend on someone reading meters by hand.

Name the responsible party in the statement. On a scheme where a management company will be formed after occupation, the obligation has to be written into the management arrangements or it will not be met, and the condition will sit undischarged for years.

Regulated against unregulated emissions

The hierarchy is applied to regulated emissions: space heating and cooling, hot water, ventilation, pumps and fans, and fixed internal lighting. Unregulated emissions from appliances, cooking and small power sit outside the building regulations calculation.

Report both, and label them clearly. A statement that quotes a percentage saving without saying whether the denominator is regulated emissions alone invites a question, and where local policy requires total emissions to be addressed the unregulated figure has to be there.

Embodied carbon is a separate exercise again, reported through a Whole Life Carbon Assessment rather than inside the energy hierarchy, and the reuse of existing structure covered in our note on the material inventory in a pre-redevelopment audit belongs there. Councils normally expect a suitably qualified author for a whole life carbon assessment and professional review is strongly advised.

Reporting the residual shortfall

After be green there is usually something left, and the statement has to quantify it in tonnes of carbon dioxide per year and over the assessment period the policy uses.

Illustrative example: a 96 unit scheme with a baseline of 142 tonnes per year of regulated emissions, reduced to 108 tonnes after be lean, to 71 tonnes after a communal heat pump system at be clean, and to 58 tonnes after a rooftop array at be green. The residual 58 tonnes was the figure the offset contribution was calculated from. The figures are illustrative and used to show the reporting chain.

Where a payment is required to address the residual, it is secured through a planning obligation and calculated from the shortfall, the price per tonne in the adopted policy and the period the policy applies. Check that price against the current adopted document, because it is reviewed.

Put the four figures and the residual in a single summary table at the front of the Energy Statement. And keep that table consistent with the modelling output appended to it, because a mismatch between the summary and the appendix is the single most common reason an energy statement is returned. Browse all 66 PlanScope report types and start a draft.

This is general guidance, not legal advice, and the applicable targets and reporting requirements vary by authority, so check the adopted development plan and take advice from a qualified building physics adviser before relying on it.

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