Energy statements for a major refurbishment

An energy statement for a refurbishment scheme is a harder document than its new-build equivalent, because the baseline is a real building rather than a notional one and because half the measures you would like to propose are ruled out by structure you are keeping. The common failure is to write it as though the building were new, present percentage improvements against a notional baseline nobody recognises, and leave the officer unable to tell whether the scheme is ambitious or lazy.

The better approach starts with what the building does now, states what the retained fabric and frame prevent, and then shows what is left.

What triggers an energy statement on a refurbishment

Three separate triggers operate, and a scheme can engage all of them.

A development plan policy threshold, usually set at major development. Most adopted plans apply their energy policies to refurbishment and change of use as well as to new build, although the wording often reads as though new build were intended. Read it closely, because a policy requiring a percentage reduction "against Part L" means something different for an existing building.

A local validation requirement, which can ask for an energy or sustainability statement at a lower threshold than the policy applies to.

A Building Regulations trigger, which is not a planning matter but shapes what the statement can promise. Regulation 28 of the Building Regulations 2010 requires consequential improvements where the existing building has a total useful floor area over 1,000 square metres and the work involves an extension, the initial provision of fixed building services, or an increase in the installed capacity of a service. That obligation surprises clients, and it is better raised at planning stage than during technical design.

Where the building is listed or in a conservation area, the energy statement also has to engage with the heritage position, because the measures that deliver most of the saving are usually the ones that alter the external appearance.

Baselining the existing building honestly

An energy statement that baselines against a notional Part L building for a structure built in 1972 is not describing anything real, and officers have become sceptical of it.

Four sources give a defensible baseline, in descending order of usefulness.

1. Metered consumption. Half-hourly electricity data and gas meter readings over a full year, normalised for degree days and for occupancy, tell you what the building actually uses. Nothing else comes close.
2. An as-existing model built from a measured survey, with U-values derived from opening up rather than from assumed construction.
3. The current energy performance certificate, which is a modelled figure produced for a different purpose and should be labelled as such.
4. Benchmarks for the building type, used only to sense-check the above.

State which you used and why. Where consumption data exists but the building has been partly vacant, say so and explain the adjustment rather than quietly using the low figure.

Report regulated and unregulated energy separately, and give an energy use intensity figure in kilowatt hours per square metre per year over the whole building. That single number is what makes a refurbishment comparable with a new build and with a published target, and it is increasingly what a planning officer asks for.

Which regulations bite on which element

The Building Regulations treat an existing building element by element, which is why a refurbishment can be a patchwork of standards.

The "technically and functionally feasible" qualification is where most of the argument happens. It is a real exemption, not a convenience, and the justification needs to be recorded with reasons rather than asserted. A retained solid wall where internal insulation would leave a room below the minimum dimension is a feasibility point. A retained solid wall where insulation is simply expensive is not.

For domestic retrofit, the PAS 2035 framework governs the assessment, design and risk management process, and referencing it in the statement reassures an officer that moisture risk has been considered rather than ignored.

Measures the retained structure rules out

This is the section that distinguishes a credible refurbishment statement from a template, and it should be specific to the building.

External wall insulation is usually the biggest single improvement available and is frequently unavailable, because the elevation is of interest, because the building sits on the back of the pavement with no room to thicken the wall, or because the window reveals cannot take the extra depth.

Internal insulation costs floor area, shifts the dew point and creates junction details at every floor slab and internal partition. The condensation risk analysis belongs in the statement, not in a later package, and the junctions are where it will be won or lost. The reasoning in thermal bridging detail at planning stage applies with more force to an existing frame, because exposed slab edges and concrete balconies cannot be redesigned.

Airtightness is limited by the construction you are keeping. A 1960s frame with an infill panel facade will not reach new-build figures without replacing the facade, which changes the scheme.

Plant and risers constrain the services answer. Heat pumps need external space, acoustic separation and riser capacity that an older building was never given, and the electrical supply may need reinforcement. Where a heat network exists or is planned nearby, safeguarding a future connection is often the most deliverable answer and costs little at design stage.

Overheating is the measure that bites back. Improving the fabric of a deep-plan or single-aspect building without addressing solar gain and ventilation produces a worse summer than the one you started with. Commission the Overheating Risk Assessment alongside the energy work rather than after it, particularly on upper floors and under new roofs.

Counting the carbon that retention saves

Retention saves upfront embodied carbon, and the saving is real, but it has to be counted against something.

Set out the retained elements by quantity, then report the modules of the Whole Life Carbon Assessment separately so the reader can see which savings come from avoided new material, which from avoided demolition and disposal, and which from avoided transport. Keep the retained quantities identical to those in the structural drawings, because an inconsistency between the two documents undermines both.

Three traps recur. Strengthening and remedial works to retained elements are new material and belong in the product and construction modules. A longer assumed design life reduces annualised carbon and has to be justified rather than chosen. And refurbishment often has higher replacement cycles for services, which shows up in the in-use modules and should not be omitted.

Carbon assessment to the current RICS methodology is work councils expect a suitably qualified author to carry out, and professional review is strongly advised before anything is submitted.

Setting up the demolition comparator

Where the policy requires a comparison with demolition and rebuild, the comparator does most of the arguing, so define it explicitly.

Fix the floor area, the use mix and the design life on the same basis for both options. Include demolition, transport and disposal in the redevelopment case. Then report upfront carbon and operational carbon separately over a stated period, because an efficient new building can have lower operational carbon while carrying a much larger upfront cost, and the crossover point is the honest answer to the question.

Say what the crossover is. A statement that reports only the upfront saving, on a scheme where the new build would be meaningfully more efficient in use, invites an officer to do the arithmetic themselves and reach a different conclusion.

The evidence that carries the retention case

Five documents, aligned with each other, make the case.

A structural appraisal with capacity, condition and adaptability treated separately. A measured survey with opened-up U-value evidence. Metered consumption data for the existing building. The whole life carbon assessment with the comparator set out. And the Energy Statement itself, which should cross-reference the other four rather than restate them.

Where the authority also asks for a sustainability statement, decide which document answers which policy and avoid saying the same thing twice in different numbers. Two documents that disagree is the most common reason a refurbishment energy case loses credibility, and it is entirely avoidable.

Enter your postcode on PlanScope to see which reports a refurbishment scheme on your site is likely to need.

This is general guidance, not legal advice. Check the 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.