Many homeowners and landlords are pleasantly surprised by how straightforward an EPC assessment is. Your assessor won’t move furniture, open up walls, or spend hours going through every cupboard. Most domestic assessments are completed within an hour or so, and you can carry on with your day while the work is done.
That said, knowing what to expect, and what to have ready beforehand, can make the process smoother. In some cases it can even help you achieve a better rating.
Here’s a clear, room-by-room look at what your assessor is checking, and why each element matters.
First: Which Methodology Does Your Assessor Use?
Domestic EPC assessments in England and Wales are based on a government-approved calculation method called RdSAP, which stands for Reduced Data Standard Assessment Procedure. Since June 2025, all new domestic assessments use the latest version, RdSAP 10.
RdSAP 10 is more detailed and evidence-based than its predecessor. Where older versions often relied on assumptions about things like window performance and lighting, RdSAP 10 requires assessors to measure and record more precise data. The result is a certificate that more accurately reflects how your home is performing.
A new methodology called the Home Energy Model (HEM) is due to launch in the second half of 2027. From 1 October 2029, new assessments must use HEM. Until then, RdSAP 10 remains the standard, and any EPC achieved under RdSAP 10 before that date remains valid for its full 10-year period. This guide is based on the current RdSAP 10 methodology.
The Exterior and Building Details
Before stepping inside, your assessor will note the basics: property type (detached, semi-detached, terraced, flat), construction style, approximate age, and total floor area. These details form the foundation of the rating because they determine how well the building retains heat as a baseline.
Under RdSAP 10, properties built from 2023 onwards are assigned to a new age band (Band M), which reflects modern construction standards. If your property is relatively new, this can work in your favour.
Living Rooms and Bedrooms
Windows
Windows are a major factor in heat loss, and RdSAP 10 introduced a significant change here. Your assessor must now measure every single window individually. This includes its dimensions, glazing type (single, double, or triple), frame material, orientation, draught-proofing status, and whether any shutters are present.
Previously, assessors could apply assumed values based on the property’s age. Now, each window is assessed on its own merits. This is better news for homes that have been upgraded, because modern double or triple glazing will be properly recognised rather than estimated.
If you’ve had windows replaced, having the installation paperwork available will help ensure the improvement is captured accurately.
Lighting
Under RdSAP 10, assessors count individual bulbs rather than just light fittings, and each bulb is recorded by type: LED, CFL (compact fluorescent), or incandescent. This provides a more accurate picture of lighting energy use.
Switching to LED throughout the property is one of the quickest and most affordable changes you can make before an assessment. It’s a small investment that can nudge your rating in the right direction.
The Kitchen
In the kitchen, your assessor will check lighting in the same way as other rooms. They’ll also record any extractor fans, which feed into the ventilation picture for the whole property. Under RdSAP 10, ventilation is assessed in more detail than before, so extractor fans are now recorded more carefully as part of this.
Bathrooms and En Suites
Ventilation is recorded throughout. Extractor fans in bathrooms and en suites contribute to the overall ventilation assessment. Your assessor may also note blocked chimneys, flues, or stack vents elsewhere in the property. Accurate ventilation data helps produce a fairer rating, particularly for properties that have been draught-proofed or retrofitted.
If your property has had a professional air pressure test (sometimes called a blower door test), the results can now be entered directly into the RdSAP 10 software. A well-sealed home can gain several points from this, and in some cases enough to move up a full band.
The Boiler and Heating System
This is one of the most important parts of the assessment. Your assessor will check:
The type of heating system (gas boiler, oil boiler, electric, heat pump, etc.)
The boiler make and model, if identifiable
Heating controls: room thermostat, programmer, and thermostatic radiator valves (TRVs)
The hot water cylinder, if present, including any insulation jacket and whether a cylinder thermostat is fitted
Under RdSAP 10, assessors prioritise actual evidence over default assumptions. If your boiler model is identifiable, its real efficiency rating is used in the calculation. If it can’t be identified, the software applies a generic assumption, which may underestimate the system’s performance.
Having your boiler manual, service records, or any installer documentation available on the day is genuinely helpful. Similarly, if your hot water cylinder has a thermostat and an insulation jacket, make sure they’re accessible so the assessor can see them clearly.
The Loft
Loft insulation is a big contributor to an EPC rating. Your assessor will check whether insulation is present and, where it is, record the depth and type.
If you have a room in the roof (a converted loft space), RdSAP 10 now assesses this in more detail. It distinguishes between different room-in-roof types and requires more precise measurements. If your conversion has been insulated to a good standard, any installation records will help ensure this is reflected in the rating.
Note: assessors are not required to enter a loft if it’s unsafe or unboarded. If you want your insulation properly assessed, a safe, accessible loft hatch makes a difference.
Floors
Your assessor will note the floor type (solid concrete, suspended timber, etc.) and whether any underfloor insulation is present. Floor insulation can be difficult to verify visually, particularly for suspended timber floors where insulation is fitted beneath the boards. If you’ve had this done, any relevant installation paperwork will be useful.
Renewables and Modern Technology
RdSAP 10 now properly accounts for modern energy technologies that older versions of the methodology handled less accurately. If your property has any of the following, your assessor will record them:
Solar photovoltaic (PV) panels
Battery storage systems
PV diverters (which direct surplus solar energy to heat your hot water)
Air source or ground source heat pumps
Mechanical ventilation with heat recovery (MVHR)
Installation certificates and any manufacturer documentation will help ensure these are captured correctly and credited to your rating.
Will the Assessor Need Access Everywhere?
For most properties, your assessor will need to:
Walk through all rooms (though not every identical room, for example, if two bedrooms are the same size and layout, they’ll only need to assess one)
Access the loft hatch (but not enter if it’s unsafe or unboarded)
See the boiler, heating controls, and hot water cylinder
What they won’t need to do: move furniture, lift floor coverings, remove ceiling boards, or access any space that isn’t safely reachable.
It’s also worth knowing that the assessment rates the property itself, not the current occupants’ energy habits. The software uses standardised assumptions for heating patterns and occupancy, so how you actually use the heating won’t affect the outcome.
FAQs: EPC Assessment Questions Answered
Is a property inventory a legal requirement?
No, there is no legal requirement in England for landlords to produce an inventory. However, without one, it is extremely difficult to make a successful deposit deduction if a tenant disputes it. In practice, a thorough inventory is one of the most important documents a landlord can have.
What is the difference between a check-in report and an inventory?
An inventory is the document that records the condition and contents of the property. A check-in report is the process of going through that inventory with the tenant at the start of the tenancy and getting them to agree to it. Both are needed: the inventory provides the record, and the check-in process confirms that the tenant has accepted it.
What happens if I do not have an inventory and a dispute arises?
Without an inventory, it is very difficult to prove the condition of the property at the start of the tenancy. Deposit adjudicators rely on evidence, and without a baseline record, most decisions will go in the tenant's favour. This is why it is important to produce a thorough inventory before the tenancy begins, not after a problem has arisen.
Do I need a new inventory for each tenancy?
Yes. Each new tenancy should begin with a fresh inventory that accurately reflects the current condition of the property. Using an old inventory from a previous tenancy is risky, as the condition of the property may have changed and the new tenant will not have signed to confirm it.
Can a tenant refuse to sign the inventory?
A tenant cannot be forced to sign, but refusal is unusual. If a tenant has concerns about the recorded condition of the property, these should be noted and addressed at check-in rather than left unresolved. Giving the tenant a reasonable window to review and raise any queries after check-in is good practice.
Book Your EPC with EPC247
EPC247 are a family-run business based in Hull, providing domestic and commercial EPC assessments across the Yorkshire and Humber region. Our fully accredited assessors are trained to the latest RdSAP 10 standard, so you can be confident your certificate is accurate, compliant, and up to date.
We offer fast turnaround times, flexible appointments, and a straightforward, friendly service backed by over 350 five-star reviews.
If you have questions before booking, or want a chat about what to prepare, we’re always happy to help.
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