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EPC guide 18

EPCs for new-build homes

A new home is rated from its design and construction information rather than from a survey of what already exists. That changes how the certificate is produced, and it explains why the figure quoted in a brochure is not always the figure that ends up on the register.

Full SAP, not RdSAP

Existing homes are assessed using RdSAP, a reduced-data method in which an accredited Domestic Energy Assessor visits the property, records what can be seen and measured, and fills the gaps with standard assumptions based on age and construction type. A new dwelling does not need that inference. The specification is known on paper, so the rating is produced using the full SAP methodology from the design and construction information – insulation values, thermal bridging details, glazing, airtightness, heating, hot water, ventilation and any renewables.

SAP calculations for new dwellings also sit within the energy requirements of the building regulations, so the same modelling that demonstrates compliance produces the rating shown on the certificate. The work is carried out by an assessor accredited for new dwellings, and the finished certificate is lodged on the national EPC register in the same way as any other domestic EPC. Like every domestic EPC, it is valid for ten years. Our guide to getting an EPC covers how assessments are arranged and lodged more generally.

The sequence, design stage to completion

The first calculation happens before the home exists. A design-stage assessment models the intended specification to show that the design should comply and to give the developer a predicted rating. Where a plot is marketed before it is finished, that prediction is what appears in the sales material, often in the form of a predicted energy assessment rather than a certificate. It is a forecast of how the finished home is expected to perform.

The second calculation happens at the end. Once the home is complete, the assessment is revisited using what was actually built and installed, including any air pressure test result for that plot, and the as-built EPC is produced and lodged on the register. That lodged certificate is the statutory one. It is the version a lender, conveyancer or future buyer will find when they search the address, and the only one you should treat as final. An EPC is required when a home is built, and again when it is sold or let.

Why the two figures can differ

Specifications move during a build. A window or door supplier may be substituted, an insulation product swapped for something the contractor considers equivalent, a boiler or heat pump replaced with a different model, a solar array resized or repositioned, or a ventilation strategy revised. Each of those changes feeds different inputs into the calculation, and the result can land above or below the design-stage prediction.

Measured results matter too. Airtightness is tested rather than assumed, and the tested figure for your plot may be better or worse than the value used at design stage. Junction and thermal bridging details as built may not match the details modelled earlier. None of this is automatically evidence of poor work – it is the ordinary gap between an intended specification and a completed one – but it does mean the brochure figure was an expectation, not a guarantee.

What to ask for on completion

  • The as-built EPC lodged on the national register for your specific plot – not the design-stage prediction.
  • Confirmation that the address, floor area and room count on the certificate are correct.
  • The air pressure test result for your plot, where one was carried out.
  • Commissioning paperwork for the heating, hot water and ventilation systems.
  • The full handover pack, including manuals, warranties and the home user guide.

Checking the certificate yourself

You can look the address up on the national register once the certificate has been lodged. The efficiency rating runs from A at 92–100 points, through B at 81–91, C at 69–80, D at 55–68, E at 39–54 and F at 21–38, down to G at 1–20. Read past the headline band and check the property description and the list of features: walls, roof, floor, windows, main heating, hot water, ventilation and lighting should all describe what was actually installed in your home. Our guide to reading an EPC explains what each part of the certificate is telling you, and the recommendations section is worth reading even on a new home.

It is worth remembering that the efficiency rating is cost-based, modelling the expected cost of energy for a standard pattern of use rather than measuring carbon or your actual bills. That is why two homes with similar fabric but different heating systems can sit in different bands, and why cost and carbon outcomes can move in different directions. If something on the certificate is plainly wrong – the wrong heating system, a missing solar array, an obviously incorrect floor area – raise it with the developer and the assessor who lodged it, since any correction has to be based on evidence.

A good band is not a quality check

A high band on a new build tells you the modelled specification is efficient. It does not confirm that the insulation was installed continuously and without gaps, that ductwork was routed and sealed properly, that the heating system was commissioned correctly, or that controls and flow temperatures were set up to suit the house. Those are questions of workmanship and commissioning, and the EPC does not inspect them.

The distance between a modelled figure and a home’s real behaviour is a long-standing discussion in the industry. Treat the certificate as one document among several: your snagging list, the structural warranty inspection and the commissioning records cover ground the EPC never touches. If a system does not seem to be performing as expected, the commissioning paperwork is usually the first place a competent engineer will look.

If you plan to let the home

A new home bought to let is subject to the same minimum standards as any other rented property. Since 1 April 2020, a property in England and Wales cannot be let below band E unless a valid exemption is registered, and most new dwellings sit comfortably above that line. A move to a higher minimum band, commonly discussed as band C, has been the subject of government consultation rather than settled law, so treat any timetable you see quoted as provisional and check the current position before relying on it. Our guide to EPC rules for landlords sets out how the standard works in practice.

Energy performance is a devolved matter, so the detail differs between England and Wales, Scotland and Northern Ireland, including the way certificates are produced and registered. If your plot is outside England and Wales, read our guide to EPCs across the UK alongside this one and confirm the current requirements on gov.uk or the relevant national body.

Keep the handover pack

The handover documentation is genuinely useful rather than filing for its own sake. It records which products went into the house, how the heating and ventilation should be operated and serviced, and what the systems were set to at commissioning. That information saves time when something fails, when an engineer needs to adjust a control strategy, and when you are deciding which future improvements are worth making.

It also helps when you sell. A domestic EPC lasts ten years, so the as-built certificate will often still be valid, and buyers and their conveyancers will look at it alongside the warranty and handover records. Our guide to EPCs when buying or selling covers how the certificate fits into a transaction. Anything here about costs, lending or letting is general information rather than financial advice. EPC Checker is a research aid over public data; it is not an assessment, survey, or professional, legal or financial advice.