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Preparation

Re-assessment and the evidence pack

The order matters more than anything else here: gather the paperwork first, hand it over at the start of the visit, and let the assessor model the building you actually own.

The most common and most expensive mistake Commissioning the assessment first, receiving a disappointing rating, and only then going looking for evidence. By then the certificate is lodged. You can supersede it, but you have paid twice and the earlier one remains on the public register.

The evidence pack

Work through this before you book anything. Every item that exists removes an assumption.

The commercial evidence pack
DocumentWhere it usually livesWhat it settles
Construction drawings and specificationOriginal build file, architect, Land Registry-era conveyancing packWall, roof and floor construction
U-value calculationsBuilding control file, Part L compliance packFabric performance
Air permeability test certificateO&M manual, building control completion fileInfiltration rate
Cavity fill guarantee or invoiceRefurbishment records, CIGA guaranteeWall insulation
Lighting schedule and product dataFit-out contractor, M&E consultantLighting efficacy and controls
Boiler / chiller commissioning certificatesO&M manual, maintenance contractorPlant seasonal efficiency
Manufacturer performance dataPlant nameplate, model number, supplierEfficiency figures
BMS schematics and points listControls contractor, FM providerCredit for controls strategy
AHU commissioning and SFP dataO&M manualVentilation performance
Refurbishment history with datesAsset file, service charge recordsWhich age-band defaults are wrong

How to run it

  1. Pull the current certificate and note every element likely to carry a default. Look it up.
  2. Raise the file. O&M manuals, building control completion, refurbishment records, the M&E contractor, the FM provider. Ask the maintenance contractor for plant model numbers if nothing else survives.
  3. Index it against the elements it settles, so the assessor is not reading a box of paper.
  4. Hand it over at the start of the visit, not afterwards. An assessor who has the evidence before modelling does not have to enter a default and revisit it.
  5. Walk the building with them and point out what is not visible – the plant replaced last year, the insulation above the suspended ceiling, the zoning that was added.
  6. Keep the pack. It serves the next assessment, any exemption bundle, and due diligence.
Where nothing survives Buildings bought second-hand often have no handover file at all. Two routes are usually open: an opening-up inspection to establish construction (cheap, destructive in a small and repairable way), and an air permeability test (a day, and often the single highest-value piece of evidence on a modern building).

What an assessor can and cannot do

An accredited assessor cannot enter a value they have not seen or been shown. They are not being obstructive when they record a default – they are applying the conventions, and departing from them is what gets certificates audited and withdrawn.

Which is also why "find a more helpful assessor" is not a strategy. Two competent assessors given the same evidence reach materially the same rating. Change the evidence, not the assessor.

We can do this part for you

evenEco's assessors gather the evidence, identify the assumptions worth attacking, and carry out the assessment – so the model describes the building you actually own.

Common questions

Will a new assessment automatically give me a better rating?

No. It will give you an accurate rating. That is better than a cautious one only if the caution was unwarranted – which is why the evidence gathering comes first and the assessment second.

Can I have a second EPC done if I do not like the first?

You can commission a new assessment at any time, and the most recent valid certificate is the operative one. But shopping for a better number without new evidence does not work, and lodging certificates you then ignore leaves a visible trail on the register.

How long does the evidence gathering take?

For a single building with a reasonable O&M manual, days. For a building bought second-hand with no handover file, it can take weeks and may involve going back to the previous owner or the contractor.

Written and reviewed by the evenEco assessment team Last updated Figures from the GOV.UK Energy Performance of Buildings Register, non-domestic extract for England & Wales, analysed 11 September 2026 How we produce this