What Happens During ECO4 Home Survey

What Happens During an ECO4 Home Survey? What to Expect at Every Stage

An ECO4 home survey is not a quick look around. Under the PAS 2035 standard, which all ECO4 installations must comply with, a Retrofit Assessment is a structured, data-led inspection that typically takes two to four hours in a standard domestic property. Understanding what the assessor actually does, what they are looking for, and what happens with the results removes the uncertainty that most households feel when they receive the appointment.

Important: InstantGrant is an independent grant information and application-support service. We are not Ofgem, the UK government, or any energy supplier. We do not carry out Retrofit Assessments or determine which measures your property qualifies for. All information on this page is drawn from the PAS 2035:2019 Specification for Retrofit, Ofgem ECO4 Consumer Guidance, and Retrofit Academy Assessor guidance as of September 2026. Always confirm the specific scope of your survey with the assessor before the visit.

PAS 2035 was introduced by the British Standards Institution in 2019 specifically because thousands of properties received poor-quality insulation under earlier ECO and Green Deal schemes. Cavity wall insulation was installed in properties with pre-existing dampness. Solid wall insulation was fitted without adequate ventilation assessment. The results caused damp, mould, and in some cases structural damage. The survey process exists to prevent this from happening again, and understanding why each element of the survey matters helps households engage with it properly rather than seeing it as a formality.

What Happens During an ECO4 Home Survey: The Three Components

Component 1: The Occupancy Interview

The first thing the assessor does when they arrive is not look at the walls or the boiler. It is to talk to you.

The occupancy interview is a formal part of the PAS 2035 assessment. The assessor needs to understand how the property is actually lived in before making any observations about what it needs. The questions typically cover:

How many people live in the property and in which rooms they spend most of their time.

How you currently heat the home — which rooms you heat, at what temperatures, and at what times of day.

Whether you have noticed specific comfort problems: cold rooms, condensation on windows, patches of damp on walls, draughts from particular areas, or rooms that never seem to warm up.

Your hot water usage patterns — how often you use the shower, bath, or kitchen hot water.

Whether any known defects exist: a leaking roof, previous damp issues, cracked render, or known problems with the windows or boiler.

The answers to these questions directly shape what the assessor focuses on during the building inspection. A household that reports condensation in the bedroom will prompt the assessor to inspect that room's ventilation and wall surface temperature more carefully. A household that describes a chronically cold ground floor will lead the assessor to pay closer attention to floor insulation potential.

This interview is also where the assessor confirms your name, the tenure of the property (owner-occupier or tenant), and documents your consent to the assessment proceeding.

Component 2: The Building Fabric Condition Survey

The condition survey is the physical inspection of the property. The assessor works systematically through the building, recording observations about the structure, the building fabric, and any existing energy efficiency measures.

The condition survey covers:

Walls: Construction type (cavity or solid), approximate age, existing insulation if any, visible defects such as cracking, spalling brickwork, or damp staining. The assessor determines whether the wall type and condition is suitable for the insulation measures under consideration.

Roof and loft: Access to the loft space to assess existing insulation depth and coverage, roof structure condition, any signs of water ingress, and the presence of any tanks or services that would affect insulation installation.

Floors: Floor construction type (suspended timber or solid), evidence of draughts, condition of floor coverings and access points.

Windows and doors: Glazing type, approximate age, condition of seals and frames, any obvious draughts.

Ventilation: Existing ventilation provisions in each room — trickle vents, extractor fans, passive vents, air bricks. This is particularly important for the assessment because any measure that reduces airflow, such as solid wall insulation or draught-proofing, must be assessed against the property's existing ventilation to prevent condensation buildup.

Heating system: Make, model, and approximate age of the boiler or heating system, controls installed, hot water cylinder if present, condition of visible pipework and radiators.

Fixed appliances and services: Electric consumer unit, any evidence of recent electrical work, smoke or carbon monoxide detectors.

What the Assessor Records and Photographs

The assessor takes photographs of key areas as evidence. These typically include the loft space (showing existing insulation depth), external wall surfaces (showing construction type and condition), the boiler and heating controls, any areas of concern such as damp staining or cracked render, and the property exterior from each elevation.

These photographs become part of the formal assessment record. They are not for your benefit directly, but if you have concerns about any specific area, ask the assessor to document it during the survey rather than after.

Component 3: The Energy Assessment

Alongside the physical inspection, the assessor carries out an RdSAP energy assessment. RdSAP stands for Reduced data Standard Assessment Procedure — it is the methodology used for domestic energy performance calculations in the UK, the same underlying tool used for Energy Performance Certificates.

The RdSAP assessment records measurable data about the property: floor areas, room heights, window sizes, wall areas and construction, heating system details, and existing insulation levels. This data is entered into the software, which calculates the property's current energy performance and generates the data the Retrofit Coordinator needs to specify which improvements will produce the required EPC band improvement.

The RdSAP assessment is distinct from a full EPC survey, though they use similar data. The Retrofit Assessor is qualified specifically for PAS 2035 retrofit work, which involves a wider scope than a standard EPC assessment.

What Tools the Assessor Uses

A competent Retrofit Assessor arrives with several tools that allow them to gather data beyond simple visual observation:

Thermal imaging camera: Detects surface temperature variation on walls, ceilings, and floors. Cold spots on a wall can indicate missing or defective insulation. Thermal imaging can identify areas where existing cavity wall insulation has settled, bridged, or is absent.

Moisture meter: Measures the moisture content of wall, floor, and ceiling surfaces. Elevated readings can indicate dampness that would need addressing before insulation is installed.

Laser distance measurer: Rapid, accurate measurement of room dimensions for the RdSAP calculation and floor plan production.

Tablet or laptop with RdSAP software: All data is entered digitally during or immediately after the inspection.

Loft torch and measuring tape: For the loft inspection, where measuring existing insulation depth accurately is essential.

Draft detector or anemometer: Sometimes used to identify significant air movement through specific gaps or vents.

If an assessor arrives without a thermal imaging camera or any measuring equipment and relies entirely on visual observation, that is worth raising with the installer or supplier before the assessment is accepted as complete.

What Happens If the Assessor Finds Defects

PAS 2035 requires the assessor to produce a condition report that identifies any defects or risks that could affect the proposed retrofit measures. This is where the survey differs most significantly from a standard EPC inspection, which does not formally assess property condition.

Common defects found during ECO4 home surveys include:

Active dampness: Where moisture is entering the property through a roof leak, rising damp, or penetrating damp. Insulation installed over active dampness can trap moisture and worsen the problem significantly. The assessor will flag this as a condition that must be addressed before any insulation is installed.

Defective pointing or brickwork: Damaged mortar joints in a cavity wall can allow water penetration. Cavity wall insulation in a compromised cavity can accelerate damp problems rather than solving them.

Inadequate ventilation: If the current ventilation provision is already marginal, any reduction in natural air movement through additional draught-proofing or insulation requires compensating ventilation measures to be installed at the same time.

Electrical concerns: Visible wiring issues, an older consumer unit, or evidence of unsafe DIY electrical work will be noted. Depending on severity, this may need resolution before the installation proceeds.

If a defect is found, it does not automatically block an ECO4 package. It means the defect must be addressed first, or the measures must be specified in a way that accounts for it. The assessor records the defect and the Retrofit Coordinator decides how to proceed.

The Three Roles: Assessor, Coordinator, and Installer

This is the part of the ECO4 process that most households find confusing. Three distinct roles are involved in a PAS 2035 compliant retrofit, and they must be separate from each other on any medium or higher-risk project.

The Retrofit Assessor carries out the survey and produces the assessment data and condition report. They describe what the property currently is.

The Retrofit Coordinator takes the assessor's data and produces the Retrofit Design and the Medium Term Improvement Plan. They decide what should be done and in what sequence. They are responsible for ensuring the overall project is technically sound and PAS 2035 compliant. The Coordinator must hold a TrustMark-recognised qualification.

The Installer carries out the physical work to the specification produced by the Coordinator. All ECO4 installers must be TrustMark-registered and work to the PAS 2030 installation standard.

On smaller, lower-risk projects — typically a straightforward loft and cavity wall insulation package — one qualified individual can hold both the Assessor and Coordinator roles. On higher-risk projects involving solid wall insulation or heat pump installation, the roles must be held by different people.

The Medium Term Improvement Plan

After the survey, the Retrofit Assessor produces data that feeds into a Medium Term Improvement Plan, prepared by the Retrofit Coordinator. This plan sets out the sequence and specification of energy improvements for the property over time — not just the immediate ECO4 package, but a logical pathway toward the property achieving its energy performance potential.

For most ECO4 households, the immediate package is what matters. But the MTIP is also the document that protects you if future work is planned. If the plan specifies that solid wall insulation should precede a heating system upgrade for your property, an installer who pushes for the heating upgrade first is deviating from the assessed plan. The MTIP gives you a reference point.

Ask the Retrofit Coordinator or installer for a copy of the MTIP after the assessment. You are entitled to this.

How Long Does an ECO4 Home Survey Take?

A standard ECO4 home survey for a two or three-bedroom house takes two to four hours. Larger properties, those with more complex construction types such as solid walls, or those with multiple defects requiring careful documentation may take longer.

The assessor should not rush the survey to fit more appointments into their day. A rushed PAS 2035 assessment produces incomplete data, which in turn produces an inadequately specified package. If the assessor's visit feels significantly shorter than two hours for a standard house, raise this with the installer or supplier before accepting the assessment as complete.

How to Prepare for Your ECO4 Home Survey

What you do before the survey affects how efficiently it runs:

Clear access to the loft hatch. The assessor needs to enter the loft space and inspect the full area. Remove any stored items blocking the hatch or the loft ladder.

Ensure the assessor can access all rooms. Locked or inaccessible rooms cannot be assessed and will reduce the quality of the floor plan and energy calculation.

Know the approximate age of your boiler or heating system. If you have any paperwork from the original installation, have it available.

Note any specific concerns you want the assessor to document. Cold spots, visible condensation, draughty areas, or rooms that are difficult to heat should be mentioned during the occupancy interview.

If you are a private tenant, ensure your landlord has provided written consent before the survey takes place. A survey completed without landlord consent cannot proceed to installation.

What Happens After the ECO4 Home Survey

Once the survey is complete, the data passes to the Retrofit Coordinator, who produces the Retrofit Design and specifies the measures to be installed. This specification goes back to the installer and to the energy supplier's ECO4 programme for approval.

The household is then notified of the measures specified. Installation is scheduled once the specification is approved and funding is confirmed. You will be asked to sign the Ofgem Eligibility Requirements Form confirming your eligibility details and consent to the proposed works before any installation begins.

If the survey finds that no eligible measures are appropriate for your property — because the EPC is already band C or above, because the required measures cannot achieve the two-band improvement target, or because defects make installation unsafe — the installer or supplier should provide a written explanation.

What a Legitimate ECO4 Survey Looks Like vs a Red Flag

A genuine PAS 2035-compliant ECO4 survey:

• Takes at least two hours for a standard property

• Includes a conversation about your occupancy and heating habits before any physical inspection

• Involves the assessor entering the loft space

• Uses a thermal imaging camera and moisture meter

• Results in a written assessment and condition report

• Does not result in installation being booked on the same day without a formal specification being produced first

A survey that raises concerns:

• Takes 20 to 30 minutes

• Consists only of a quick visual check of the loft and boiler

• Leads to a same-day booking with no formal written specification

• Does not involve an occupancy interview

• The person doing the survey cannot confirm their PAS 2035 Retrofit Assessor qualification

If the survey does not match the legitimate profile above, contact the energy supplier or installer in writing before agreeing to proceed with any installation.

Frequently Asked Questions

How long does an ECO4 home survey take? Typically two to four hours for a standard two or three-bedroom property. Larger or more complex properties may take longer. A survey significantly shorter than two hours for a standard house may not be PAS 2035 compliant.

What does the ECO4 assessor actually look for? The assessor inspects wall construction and condition, loft insulation depth, floor type, windows, ventilation, and the heating system. They use a thermal imaging camera to detect heat loss and a moisture meter to identify potential dampness. They also conduct an occupancy interview to understand how the property is used.

Can I choose which measures I receive after the survey? No. The measures specified in your ECO4 package are determined by the Retrofit Coordinator based on the assessment data. The specification must achieve the required two-band EPC improvement for your property. You cannot request specific measures or substitute one for another.

What is a Medium Term Improvement Plan? An MTIP is the document produced by the Retrofit Coordinator that sets out the sequence and specification of energy improvements for your property over time. It covers both the immediate ECO4 package and a longer-term pathway. Ask for a copy after the survey.

What happens if the assessor finds damp or defects? Defects are recorded in the condition report. Active dampness, defective pointing, or other issues that would affect the safety or effectiveness of insulation must be addressed before installation proceeds. This may delay the timeline but protects you from insulation that would make existing problems worse.

Do I have to be home for the ECO4 survey? Yes. The survey involves an occupancy interview as well as a physical inspection. Someone who lives in the property and knows its history must be present. A neighbour or letting agent cannot substitute for this.

Can the assessor and installer be the same person? On lower-risk projects such as loft and cavity wall insulation, a qualified individual can hold both the Retrofit Assessor and Retrofit Coordinator roles. On higher-risk projects including solid wall insulation and heat pump installation, the roles must be held by separate people under PAS 2035.

What if my survey seems too short or inadequate? Contact the installer or energy supplier in writing immediately. Describe specifically what you observed and why you are concerned. Request confirmation that the survey was PAS 2035 compliant before agreeing to proceed.

How InstantGrant Can Help

If your ECO4 survey has raised questions you are not sure how to navigate — whether a defect has been properly recorded, whether your measure specification makes sense for your property, or whether the process you experienced was genuinely PAS 2035 compliant — InstantGrant can help you work through it.

InstantGrant is an independent grant information and application-support service. We help UK households understand the ECO4 process at every stage, including what should happen during and after the survey, and what to do if something does not seem right.

We are not Ofgem, any energy supplier, or any installer. We do not carry out surveys and we do not guarantee any outcome.

Get guidance at instantgrant.co.uk