DEA Minimum Evidence Requirements: A Practical Field Guide

The short version: an auditor should be able to replicate your EPC using nothing but the evidence you leave behind. Not your memory of the property, not a general impression of a “typical” 1930s semi, but the sketch plan, site notes, photographs and documents you actually captured on the day. This guide breaks down the minimum evidence requirements category by category, and adds the practical habits that make them easier to hit consistently, whether you’re newly qualified or years into practice. It draws directly on the published DEA Minimum Evidence Requirements document.

Why This Matters Beyond the Audit

It’s tempting to treat evidence requirements as an audit-compliance exercise: tick the boxes, avoid a non-compliance, move on. In practice, thin evidence is usually the same thing as a thin assessment. If you can’t evidence the loft insulation properly, there’s a reasonable chance you didn’t check it properly either. Building the evidence habit and building assessment accuracy are the same habit.

This is also a minimum list. Additional evidence may be needed depending on the property and its specific characteristics: an unusual extension, a heat pump with no visible label, a shared party wall of uncertain construction. Treat the list as a floor, not a ceiling.

Floor Plan and Site Notes

Your sketch plan needs to cover every level, with measurements and area calculations for all building parts, window measurements and orientation, internal room layout, and identification of heat loss and party walls. Keep everything metric, to two decimal places. Window measurements and orientation can go straight into site notes, mobile or paper, rather than onto the sketch itself.

Site notes carry anything mandatory that isn’t already covered by the floor plan or by photographic or documentary evidence, including the reasoning behind any judgement call. For more on keeping these organised and audit-ready, see our article on managing site notes and records.

Photographic Evidence, Category by Category

Photos must be clear, date stamped and geo-tagged where possible. A single photo can evidence several elements at once, and photos are only required where genuinely applicable to the property being assessed. For general best practice on capturing and organising your images, see our article on photography for EPC assessments; the categories below are the specific items that photography needs to cover.

All dwelling elevations

• Front, rear and, where appropriate, side elevation
• All alternative wall types shown clearly in elevation evidence
• Unheated corridors leading to the entrance of a flat or maisonette

Construction

• Wall and party wall construction type
• Wall thickness for any building part, including alternative walls
• Roof and floor construction types
• Conservatories: evidence of separation and heating, if heated

Insulation

• Wall insulation: evidence of cavity drill pattern, or external/internal wall insulation evidence, or documentary evidence confirming presence and thickness
• Loft or room-in-roof insulation: a photo of measured thickness plus an overview of the loft confirming the recorded level extends across the loft area; where the detailed assessment method is used, photos or documentary evidence must confirm room-in-roof elements are insulated as recorded. Where access is genuinely restricted, see our guide on reporting loft insulation with blocked access
• Floor insulation: clear visual or documentary evidence
• U-value calculations, if any have been overwritten

Openings

• Windows: at least one photo of each differing glazing type, age or draught-proofing; a FENSA certificate where glazing details are known
• External doors

Lighting

• One example of each different lamp type within a fixed fitting

Space heating

• Primary heating system, including boiler or heat pump ID label, key features, pump age and flue type
• All heating controls being recorded
• Emitters
• Fuel tank or storage (LPG/oil)
• Secondary heating system, including fuel where possible

Water heating

• Hot water cylinder details: size, thickness, thermostat if applicable, and declared cylinder heat loss if present
• Shower types
• WWHRS evidence
• FGHRS evidence

Ventilation

• Chimneys, flues, fans, vents and flueless devices
• Air pressure test certificate
• Mechanical ventilation details: type, database details, duct type, duct insulation

Renewables

• Solar PV/hot water, plus external photos for roof coverage; documentary evidence (e.g. MCS) for exact details
• Solar diverter
• Batteries: evidence of storage capacity being recorded
• Wind turbines
• Hydro, with evidence confirming power generation

Meters

• Gas and electric meters, showing dual rate or tariff, or smart/export ability

Documentary Evidence: The Rules That Apply

Documentary evidence can stand in for a photograph, or sit alongside it, where a photo isn’t obtainable or where a document gives a clearer confirmation of a data item. Three rules govern its use under RdSAP Convention 9.02:

• It must be specific to the property being assessed, not a generic manufacturer spec sheet or a certificate for a different installation
• It must be sufficient on its own for an auditor to independently verify the item
• It must not be used as a default substitute for a site visit or a photograph where photographic evidence was reasonably obtainable, and where it is used instead, the reason must be recorded in the site notes

Pitfalls Worth Avoiding

• A single loft photo taken from the hatch, with nothing confirming the recorded depth extends across the whole loft
• Elevation photos that miss an alternative wall type on a side return or extension
• Reaching for a certificate as the default instead of a two-minute photo, with no note explaining why
• Heating controls photographed but not identified clearly enough to confirm the exact type recorded
• Meter photos that don’t show enough of the label to confirm tariff or smart capability

Quick Reference Checklist

If you’re working through RdSAP 10 conventions as part of your mentoring, or want to talk through how to build this evidence routine into your own assessment workflow, get in touch through DEA Launchpad.

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