Energy evidence for a refurbishment or retrofit application
Retrofit energy evidence sits across two regimes that ask for different things. This sets out what a planning case officer can require, where the Building Regulations take over and how to sequence the consents.
Retrofit energy evidence for a planning application covers a narrower field than most applicants expect. Planning controls the appearance and impact of what you are building; the thermal performance of the fabric is dealt with under the Building Regulations, on a separate application, to standards that differ from new build. So an energy statement for a refurbishment is mostly about which measures need permission, what they will look like, and how the building's performance improves, rather than about calculated compliance.
What planning can and cannot ask of an existing building
A local planning authority can only require information that is needed to determine the application against adopted policy. Where the local plan has a policy on carbon reduction or energy performance that applies to conversions and change of use, a short Energy Statement answering that policy is reasonable. Where the works are simply a re-roof and new windows on an unlisted house, it is not.
Two things regularly get confused. A council cannot use planning conditions to impose a fabric standard that the Building Regulations already govern, because that duplicates another consent regime and fails the necessity test in the Planning Practice Guidance on conditions. It can, however, refuse permission for cladding that harms the character of a conservation area, and it can condition materials and detailing.
Conversions are the exception worth knowing. Where a change of use creates dwellings, many local plans apply their residential energy policy to the new units, and in London the London Plan energy hierarchy applies to major schemes including conversions. Check the adopted policy wording before deciding what to submit.
Where the Building Regulations bite on refurbishment
Approved Document L contains separate provisions for work on existing buildings, and they are looser than the new build standards in three respects. Replacement elements have to meet a target U-value for that element rather than a whole-building target. Thermal elements being renovated have to be upgraded where it is technically and functionally feasible with a simple payback inside the stated period. And controlled fittings such as windows and doors have their own standards.
This is why a like-for-like window replacement in a solid wall house does not drag the whole wall build-up into scope. It is also why an applicant who assumes "retrofit means Passivhaus levels" over-specifies and then cannot afford the scheme.
Historic and traditionally built buildings need a different approach again. Solid walls of lime-bonded stone or soft brick manage moisture by breathing, and sealing them with impermeable insulation causes interstitial condensation and decay. Historic England's technical advice on energy efficiency in historic buildings is the reference point, and a case officer in a conservation area will expect to see that it has been read.
Consequential improvements and the 1,000 m² trigger
Regulation 28 of the Building Regulations 2010 requires consequential improvements to the energy performance of an existing building where the building has a total useful floor area over 1,000 m² and the proposed work consists of an extension, the initial provision of a fixed building service, or an increase to the installed capacity of a fixed building service.
The improvements have to be made only where they are technically, functionally and economically feasible, and Approved Document L Volume 2 sets a value benchmark tied to a proportion of the cost of the principal works. For a landlord extending a 1,400 m² office or replacing its boiler plant, that can mean upgrading lighting, controls or insulation elsewhere in the building as part of the same project.
It bites on commercial conversions more often than people expect. A 1,200 m² former warehouse being converted and extended crosses the threshold on floor area, and the mechanical plant installation crosses it on the second limb. Budget for it at appraisal, not at building control stage.
Measures that need permission and measures that do not
Much of a retrofit programme is permitted development on a dwellinghouse, subject to the conditions in the General Permitted Development Order 2015. The distinctions that matter:
| Measure | Usual position on a house outside a designated area |
|---|---|
| Internal wall insulation | No planning permission needed |
| Replacement windows in similar appearance | Permitted development under Part 1 Class A |
| External wall insulation on a rear or side elevation | Often permitted development if materials are similar in appearance |
| External wall insulation on the principal elevation | Usually needs permission because appearance changes |
| Roof-mounted solar panels | Part 14 Class A, subject to projection and siting limits |
| Air source heat pump | Part 14 Class G, subject to size, siting and noise conditions |
| Flat roof insulation with a raised parapet | Depends on the resulting height and Part 1 limits |
Article 4 directions change the answer. Many conservation areas and some whole streets have directions removing householder rights for elevations fronting a highway, and a growing number of authorities have made directions covering windows and external insulation specifically. Check the designation before you rely on the table above.
Listed buildings need listed building consent for anything affecting character, inside and out, and that includes internal insulation, secondary glazing frames and flue penetrations. The consent is free of fee. The evidence burden is not.
External wall insulation and the elevations that cause trouble
External wall insulation on a nineteenth century terrace is where planning and building performance collide. Adding 90 to 120 mm of insulation plus render changes the reveal depth around windows, loses the shadow line on the eaves, buries decorative brickwork, and pushes the wall face past the property boundary on a back-of-pavement frontage.
Officers rarely object to the principle. They object to the detailing. Deep window reveals retained with insulated returns, a proper drip at the eaves, a plinth detail at ground level and a render finish matching the local palette will get a scheme through where a flush, featureless elevation will not. Where the front elevation cannot take insulation, internal insulation to the front rooms with careful moisture design is the usual compromise.
Illustrative example: a 1900s mid-terrace where external insulation is applied to the rear and gable, internal insulation to the front wall of two bedrooms, loft insulation topped up, and an air source heat pump sited in the rear garden 2 m from the boundary with an acoustic assessment against the noise condition. Details here are illustrative only.
Evidence a case officer will accept
Keep the submission proportionate to the policy being answered:
- A short schedule of measures with the existing and proposed U-values for each element
- The current EPC and, where the policy asks for an outcome, an assessment of the rating after the works
- Elevations and typical details at 1:5 or 1:10 showing reveals, eaves and junctions where insulation changes the profile
- A moisture risk note for any solid wall work on a pre-1919 building
- Manufacturer data for any external plant, with the noise level at the nearest window
- A statement of which measures need permission and which are permitted development, so the officer knows the scope
For rented property the minimum energy efficiency standard for domestic private rented homes sits behind all of this, and government has consulted on raising the required rating. Treat the current published requirement as the floor and check the position before you commit a programme.
Sequencing the consents so nothing is abortive
Order matters, and getting it wrong wastes money. Apply for planning permission or listed building consent for anything that changes external appearance before ordering materials, because insulation thickness and render colour are exactly the things officers negotiate. Settle the heat pump location and its noise case before the electrical design is fixed, since moving a unit usually means moving the pipework run. And confirm whether regulation 28 applies before the contract sum is agreed.
Where a scheme also triggers an overheating assessment, because the change of use creates new dwellings, read the Overheating Risk Assessment requirements alongside the energy work rather than after it. Our notes on biosolar roofs and the interaction between energy, drainage and biodiversity and on ground source heat pumps and borehole permitting cover two cases where the sequencing catches people out.
See PlanScope pricing if you want to draft the energy evidence yourself and send it for professional review.
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.
Frequently asked questions
Does a refurbishment need an energy statement for planning?
Only where an adopted local plan policy requires one for that type of development. Many authorities apply their energy policy to conversions and to changes of use that create dwellings, and few apply it to straightforward repairs. Read the policy wording and the local validation list before preparing anything.
Do the Building Regulations apply the same standards to retrofit as to new build?
No. Approved Document L sets element-by-element standards for work on existing buildings, covering replacement thermal elements, renovated thermal elements and controlled fittings such as windows. They are less demanding than the whole-building targets for new dwellings, and feasibility and payback tests apply to upgrades.
When are consequential improvements required?
Regulation 28 of the Building Regulations 2010 applies where an existing building has more than 1,000 m² of total useful floor area and the work is an extension, the first installation of a fixed building service, or an increase in the capacity of one. Improvements are required only where technically, functionally and economically feasible.
Is external wall insulation permitted development?
On a house outside a designated area, insulation and render on a rear or side elevation is often permitted under Part 1 Class A where the materials are similar in appearance. Work to the principal elevation normally needs permission because the appearance changes. Article 4 directions and conservation area status remove these rights in many streets.
Do I need listed building consent to insulate a listed house?
Almost certainly yes, including for internal insulation, secondary glazing and flue penetrations, because they affect character. There is no fee for the application. Expect to submit a moisture risk assessment and detailed drawings, and expect the authority to weigh the energy benefit against harm to the building's special interest.
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.