You’ve invested thousands in cavity wall insulation, topped up your loft, or replaced your old boiler. The work is done, the property feels warmer, and you’re confident your EPC rating will improve.

But when the assessor arrives, they can’t find evidence of the improvements. The insulation is hidden behind walls or under floorboards. There are no invoices, no installation certificates, no dated photographs.

Result? The EPC software defaults to “unknown” or “assumed none” — and your rating stays exactly where it was, despite spending money on genuine upgrades.

This post explains why documentation matters, what assessors are legally required to verify, and how to protect your investment with proper records.

Key Takeaways

• EPC assessments are non-invasive — assessors cannot drill, lift floors, or open walls.
• Hidden improvements require documentary evidence to be recognised.
• Accreditation schemes audit assessors and require proof for any claimed upgrades.
• Without evidence, the software assumes worst-case scenarios that lower your rating.
• DIY work needs dated, geotagged photographs — apps like SoloCator provide verifiable proof.

Why EPC Assessments Are Non-Invasive

EPC assessments are designed to be quick, non-disruptive surveys that rely on visible evidence and accessible areas. Assessors are not permitted to conduct invasive inspections.

This means no drilling into walls to check cavity insulation, no lifting floorboards to inspect underfloor insulation, no removing radiator covers to verify boiler specifications, and no opening sealed loft hatches without permission.

This approach protects homeowners from property damage and ensures assessments can be completed quickly and affordably. However, it also means that improvements hidden behind walls, under floors, or in inaccessible lofts cannot be visually verified during the visit.

What Happens When There’s No Evidence?

EPC software operates on strict logic. If an improvement cannot be verified through visual inspection or documentary evidence, the software applies a default assumption — and those assumptions are almost always conservative.

For example, if cavity wall insulation cannot be confirmed, the software assumes the cavities are unfilled. If loft insulation depth is unknown because the hatch is sealed or inaccessible, the software may assume minimal or no insulation. If a boiler model cannot be identified and no installation certificate is available, the software assumes an older, less efficient standard.

These assumptions can reduce your EPC rating by 10, 20, or even 30 points — despite the fact that the actual improvements exist.

Why Assessors Must Follow Strict Rules

EPC assessors are regulated by accreditation schemes such as Elmhurst, Quidos, and Sterling. These schemes conduct regular audits to ensure assessors are following the correct procedures and not making unsubstantiated assumptions.

If an assessor claims a property has cavity wall insulation without evidence, and the claim is later challenged during an audit, the assessor faces disciplinary action — including potential suspension or removal from the register.

As a result, assessors are conservative. If they cannot see the improvement or verify it through documentation, they cannot include it in the assessment — even if the homeowner insists the work has been done.

What Counts as Acceptable Evidence?

Assessors can accept various forms of evidence to verify energy efficiency improvements, provided the documentation is credible and specific to the property being assessed.

For Professional Installations

• Invoices or receipts showing the work carried out, materials used, and property address
• Installation certificates (e.g., FENSA for windows, Gas Safe for boilers, cavity wall insulation guarantees)
• Building control sign-off for works requiring approval
• Manufacturer warranties or guarantees issued at the time of installation
• Dated photographs showing the work in progress or upon completion

For DIY Work

DIY improvements are more difficult to verify because there is no third-party installer to provide certification. However, they can still be recognised if properly documented.

• Dated, geotagged photographs showing the work in progress and completed (apps like SoloCator embed date, time, and GPS coordinates into the image metadata, providing verifiable proof)
• Receipts for materials purchased, showing product specifications and quantities
• Detailed written records of what was installed, when, and where

The key is that the evidence must be contemporaneous (created at the time of the work) and verifiable (not easily fabricated after the fact).

Common Scenarios Where Evidence Is Missing

Cavity Wall Insulation Installed Years Ago

Many Bristol properties had cavity wall insulation installed under government schemes in the 1990s or 2000s. Homeowners have since lost the paperwork, and there’s no external evidence of the work.

Without documentation, the assessor cannot confirm the insulation exists — and the EPC assumes the cavities are unfilled.

Loft Insulation Topped Up by the Homeowner

A homeowner buys insulation from a DIY store and tops up their loft to 270mm. No photographs were taken, and the receipt has been discarded.

The assessor can see there is insulation, but without evidence of the depth or recent addition, the software may assume a lower thickness or older, compressed material.

Boiler Replaced but No Certificate Retained

A new condensing boiler was installed three years ago, but the homeowner cannot find the Gas Safe certificate or invoice. The boiler model plate is obscured or damaged.

The assessor cannot verify the boiler efficiency without documentation, and the software may assume an older, lower-efficiency standard.

How to Protect Your Investment

Keep All Installation Certificates and Invoices

Create a dedicated file (physical or digital) for all energy efficiency work carried out on your property. Include invoices, certificates, warranties, and any correspondence with installers.

Take Dated Photographs of DIY Work

If you’re installing insulation, upgrading lighting, or making other improvements yourself, photograph the work at every stage. Use an app like SoloCator that embeds date, time, and GPS coordinates into the image metadata — this provides verifiable proof that cannot be easily disputed.

Request Copies of All Certification

When contractors complete work, always ask for copies of installation certificates (FENSA, Gas Safe, cavity wall insulation guarantees, etc.). If they don’t provide them automatically, request them before making final payment.

Store Records with Your Property Deeds

Energy efficiency documentation adds value to your property and makes future EPCs more accurate. Store records alongside your property deeds or in a secure digital folder that transfers with the property when you sell.

What If You’ve Already Lost the Evidence?

If you’ve had work done but no longer have the documentation, you may still be able to recover evidence.

• Contact the installer: Many companies keep records of past jobs and can reissue certificates or invoices.
• Check with your local authority: Some energy efficiency schemes maintain databases of properties that received insulation or other upgrades.
• Request boiler service records: If your boiler has been serviced, the engineer’s records may include the model and installation date.
• Search your email and bank statements: Digital records of payments or booking confirmations may provide enough detail to satisfy an assessor.

If no evidence can be found, the improvement cannot be included in the EPC — but at least you’ll know for next time.

Local Considerations for Bristol Properties

Bristol has a high proportion of older properties, many of which have been incrementally improved over decades by multiple owners. Documentation is often missing, particularly for work carried out in the 1980s, 1990s, and early 2000s.

If you’re buying a property in Bristol, ask the seller for any records of energy efficiency improvements. If you’re selling, gathering this documentation before listing can help you achieve a more accurate EPC rating and avoid unpleasant surprises.

Frequently Asked Questions

Can an assessor just take my word that insulation has been installed?

No. Assessors are audited by their accreditation schemes and must base assessments on verifiable evidence. Accepting verbal claims without documentation would breach professional standards.

What if I have photographs but they’re not dated or geotagged?

Photographs without metadata are less convincing but may still be accepted if they clearly show the property and the work in progress. However, dated and geotagged images (e.g., from apps like SoloCator) provide stronger evidence.

Can I get a better EPC rating if I find the missing documentation after the assessment?

Yes. If you locate evidence after the EPC has been issued, you can commission a new assessment. The updated certificate will reflect the documented improvements.

Does this apply to commercial EPCs as well?

Yes. Commercial EPC assessments also require evidence for hidden improvements, though the assessment methodology differs. The same principles apply — keep records of all energy efficiency work.

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Planning Energy Efficiency Work?

If you’re considering improvements to your Bristol property and want to ensure they’re properly recognised in your EPC, get in touch. We can advise on what documentation you’ll need and help you plan works that deliver maximum rating impact.