What Order Should Home Energy Improvements Be Done In?

The order most UK retrofit practice follows is: repair the building first, then make the fabric airtight and insulated, then plan ventilation, then change the heating system, and only then add generation and storage such as solar panels and a battery. Scotland's Heat in Buildings Strategy puts the principle in one line: "Making buildings waste less energy through energy efficiency is the first step to zero emissions."¹ That is not a slogan but a sequencing rule: every step after the fabric work is sized against a house that needs less heat, so nothing has to be bought twice.

The reason the order matters is that work done out of sequence can be undone or made wrong by later work. Insulate without ventilation and you create moisture and air quality risks. Install a heating system before insulating and it is sized for a house that will soon need less heat. The framework that exists to prevent this is PAS 2035, introduced in 2019 as "a clear framework for best practice in the energy retrofit of domestic properties", and it "has to be managed by a qualified Retrofit Coordinator"², whose job includes sequencing measures so they do not conflict. A whole house plan written before any major spend is the household version of the same discipline.

Quick summary: fix, insulate, ventilate, heat, generate

The sequence in one table:

Start with repair. A building with damp, failing render, a leaking roof or rotten sills cannot be insulated safely, because insulation traps moisture against materials that are already wet. Only once the fabric is sound does the main sequence begin.

Next comes the fabric work: airtightness, insulation and the elimination of thermal bridges. Scotland's building standards work on Passivhaus-equivalent performance sets out the same five considerations in order: "Airtight construction, High performance insulation, Thermal bridge free design, Ventilation, Optimised energy use"⁶. Note that ventilation appears fourth on that list, not as an afterthought but as a designed part of the same package. Airtightness without planned ventilation is not an improvement; it is a problem with a lower heating bill.

Then the heating system. A boiler, heat pump or heating controls chosen after insulation is specified against the reduced heat demand of the improved house, not the wasteful one it was. Government guidance for the Boiler Upgrade Scheme repeats the point with "a reiterative paragraph on energy efficiency measures, such as insulation"⁷: sort the fabric before the heat source.

Last comes generation and storage. Solar panels and batteries on a home that still wastes heat simply offset waste rather than removing it, and a battery sized before demand is reduced is a battery bought at the wrong size. The solar, battery or heat pump question is a real one, but it belongs at the end of the sequence, not the start.

Within the fabric stage itself there is a cost ladder. The consequential improvements work considered under Part L drew on "a list of around 30 standard energy efficiency measures, from cheap measures like loft/cavity wall insulation, hot water cylinder insulation, heating controls and draught proofing, to more expensive ones like a new boiler, new windows and solid wall insulation"³. Cheap measures first, expensive ones once the cheap ones have done their work: that is the sequence inside the sequence.

The numbers underpinning the order

The headline national figure is the shrinking tail of inefficient homes. In England, the proportion of homes in the lowest EPC bands fell sharply: "the proportion within the lowest bands of E to G decreased (23% to 9%)" over the decade to 2024⁴. That is the aggregate result of millions of households doing fabric and heating work in roughly the order described above, usually with public support.

The scale that measures all of this is the EPC's A to G banding. Buildings are rated from A, "very efficient", to G, "inefficient"⁵, and the same banding is used across England, Wales and Northern Ireland, with Scotland running its own certificate on the same letters. Each certificate comes with a recommendations report, and in Scotland's version it includes "an indicative cost for each improvement"⁸, so a household can see the costed list of measures before spending anything. The English and Welsh certificate does the same, with "an indication of cost and typical savings for each improvement over 3 years"⁹.

Planning-level targets sit above the household scale: London's energy assessment guidance expects residential developments to achieve "at least a 10 per cent improvement on Building Regulations from energy efficiency measures alone", and non-residential developments 15 per cent¹³. Those figures describe new build, not retrofit, but they show the same hierarchy: fabric measures first, as the baseline everything else builds on.

Why this order matters

Three forces push work into this sequence: physics, money and grants.

The physics is the simplest. Heat lost through the fabric sets the size of everything downstream. Cut the losses and the heating system, and eventually the generation, can be smaller. This is why the Passivhaus-equivalent standards work lists airtightness and insulation ahead of "Optimised energy use"⁶, and why the Heat in Buildings Strategy calls efficiency the first step rather than one option among many¹.

The money follows the same ladder. The Part L measures list runs from draught proofing and cylinder insulation, which cost little, to solid wall insulation and new windows, which cost a lot³. Because the cheap measures cut waste quickly, they improve the case for, and reduce the size of, the expensive ones. A household that skips them pays more later for the same result.

Grants are structured around the sequence too:

• Belfast City Council describes grants "for householders to make their homes more energy efficient by installing loft, cavity wall insulation and a new boiler or heating system"¹⁴: fabric and heating, in that order, funded together.
• Local advice programmes in England do the same, referring households "for further energy efficiency improvements such as loft or cavity wall insulation and in some instances a new boiler"¹⁵.
• The Home Upgrade Grant Phase 1 was "aimed to improve energy efficiency and provide clean heat solutions for low-income households"¹⁶, efficiency first, clean heat second, in a single scheme design.
• Research into lived experience of fuel poverty in Scotland found that "where energy efficiency improvements had been made, such as insulation, this was usually as a result of support from government-funded schemes or from social landlords"¹⁷, so for many households the grant rules effectively are the order of works.

One condition overrides the whole ladder for older homes. Approved Document L states that "the energy efficiency of historic and traditional dwellings should be improved only if doing so will not cause long-term deterioration of the building's fabric or fittings"¹⁸. For a solid-wall, timber-framed or listed building, the sequence starts with understanding the fabric, and some measures may never be appropriate. The fabric first approach explains what that means in practice.

Differences across England, Scotland, Wales and Northern Ireland

The technical sequence is identical across the UK. The paperwork, the certificates and the support schemes are not.

England and Wales share the EPC system and its statistics¹¹, and England's housing stock improvement is tracked through the English Housing Survey⁴. Scotland is reforming its own certificate: the government response to the EPC reform consultation describes a new Energy Efficiency Rating and confirms "We are also developing the infrastructure required to adopt the UK Government's Home Energy Model which is about to replace SAP"¹⁹, with the reforms adding a fabric energy efficiency rating based on annual heat demand in kWh, highlighting key insulation measures installed, and providing heating system information with recommendations and modelled costs²⁰. Scottish certificates will therefore show more of the sequence itself: the fabric, then the heating, with costs.

Scotland also plans at area level. Local Heat and Energy Efficiency Strategies "aim to establish area-based plans and priorities for systematically improving the energy efficiency of buildings, and decarbonising heat"²¹, and the fuel poverty strategy includes an indicator "which will recommend to building owners the measures needed to reduce demand for heat"²². In Scotland, the order of works may be set out for a whole neighbourhood, not just one house.

Wales runs its own home energy support, and Welsh public bodies use the same retrofit framework: the Development Bank of Wales explains PAS 2035 and the Retrofit Coordinator requirement for Welsh households and landlords². Northern Ireland has its own building regulations route: Technical Booklet guidance to Part F exists "in order to uplift energy efficiency standards and carbon performance requirements for new buildings"²³, and Belfast's grant support follows the insulation-then-heating pattern¹⁴. Northern Ireland households use the same A to G EPC scale⁵.

The practical upshot: wherever you live, the order is repair, fabric, ventilation, heat, generation. What differs is which certificate records it, which advice service helps you plan it, and which grants pay for which step.

Regulations shaping the sequence

Several layers of law and regulation shape what must be done and when.

Building regulations in England require energy performance information with building control applications, including for dwellings within higher-risk buildings, a notice specifying "the target fabric energy efficiency rate, the fabric energy efficiency rate as designed, and a list of specifications"²⁴. Fabric performance is measured and declared at the design stage, which is the legal expression of fabric first.

The private rented sector has its own rules. Minimum energy efficiency standard regulations "require eligible properties in the sector to be be improved to a specified minimum standard"²⁵, and related provisions "empower private domestic tenants to request consent for energy efficiency measures that may not unreasonably be refused by their landlord"²⁵. Both sit under the Energy Act 2011, which makes "provision for the arrangement and financing of energy efficiency improvements to be made to properties by owners and occupiers"²⁶. For renters, the sequence may be driven by the landlord's compliance timetable rather than the household's preference; the page on starting when you rent covers what a tenant can do.

The whole framework descends from European legislation. Directive 2002/91/EC set out its objective "to promote the improvement of the energy performance of buildings within the Community, taking into account outdoor climatic and local conditions, as well as indoor climate requirements and cost-effectiveness"²⁷, and the Scottish register legislation lists its purposes as "Promoting energy efficiency improvements in relation to buildings" and conducting research and policy analysis²⁸. Cost-effectiveness is built into the legal intent, which is another way of saying the cheap measures come first.

Above all of this sits PAS 2035 as the practice standard², and above that, for new build and major work, the Future Homes and Buildings Standards, whose stated priorities include to "Reduce energy demand of homes and non-domestic buildings by requiring high performing building fabric and building services in new buildings, thereby improving energy security"²⁹. Reducing demand first is now policy at every level, not just good practice.

Energy independence and the order of works

The order of works is really a plan for reducing dependence, step by step.

Fabric work reduces dependence on fuel, whoever supplies it. A house that needs less heat buys less of it, from any supplier, at any price. That is why the Future Homes and Buildings Standards explicitly ties high performing fabric to "improving energy security"²⁹: demand reduction is the one energy measure that no market event can take away from you.

Heating system work changes what you depend on. Moving from gas to a heat pump or another clean heat source shifts the household from a fuel delivered by pipe and ship to electricity, which can be generated at home. The EPC reflects this: the Energy Efficiency Rating is "the first rating to appear on the EPC" and is "well-known and recognisable to most"⁹, and the reforms in both Scotland and England will add heating system information and modelled costs to the certificate²⁰, so the certificate itself will increasingly show the household's position on the sequence.

Generation and storage are the last step because they only deliver independence on a house whose demand has already been cut. A battery and solar array on a wasteful house offsets waste; on an efficient house it can cover a real share of what remains. Supplier schemes still have a role at every stage, funding "making energy-saving improvements to your home"³⁰, but each step of the sequence reduces how much of that support, and how much imported energy, the household needs.

Where the hierarchy is followed strictly or loosely

The sequence is applied firmly in standards and grant design, and loosely in the wider housing market.

It is applied firmly wherever PAS 2035 applies², wherever grants bundle insulation before heating¹⁴, and wherever building regulations measure fabric at design stage²⁴. If your work is grant-funded or needs building control approval, the order is largely decided for you.

It is applied loosely elsewhere. Governments have retreated from extending the discipline to whole tenures: Scotland's Heat in Buildings Bill consultation included the option to "Abandon proposals to require private landlords to improve the energy efficiency of their properties"³¹, and England's position on landlord requirements has shifted over time²⁵. Owner-occupiers face no legal sequence at all, which is why so much improvement work happens out of order, and why research finds improvements usually arrive only "as a result of support from government-funded schemes or from social landlords"¹⁷ rather than through planned private retrofit.

The measurement system is also still moving. Reforms to the energy performance of buildings regime are considering "updating what EPCs measure through additional metrics" and improving the accessibility of building performance data³², Scotland is adopting the Home Energy Model¹⁹, and one of the main statistical series has been discontinued¹⁰. The order of works does not change, but the numbers describing it do, so check the current position before relying on any figure.

For a household, the practical response to all this looseness is to impose the order yourself:

1. Get an assessment.
2. Use your EPC's recommendations as the costed list.
3. Write the sequence into a plan.
4. Measure the results after each stage.

The sequence is not a rule anyone will enforce on you. It is the order that stops you paying twice.