Why Does My EPC Say "Assumed"?
Many homeowners are surprised to see the word "assumed" appearing within their Energy Performance Certificate (EPC).
A common reaction is:
"Why has the assessor assumed something instead of checking it?"
In most cases, the use of assumptions is a normal part of the EPC methodology and does not necessarily indicate that anything is wrong with the assessment.
What Does "Assumed" Mean?
An EPC is produced using a Government-approved methodology known as the Reduced Data Standard Assessment Procedure (RdSAP).
Under this methodology, assessors are required to inspect the property and collect evidence. However, not every element of a building can be physically inspected during a standard EPC assessment.
Where information cannot be verified, the methodology may require the assessor to apply an approved assumption.
Why Are Assumptions Used?
Some parts of a property are hidden from view and cannot be inspected without causing damage or carrying out intrusive investigations.
Examples may include:
Insulation hidden within walls
Floor insulation beneath floor coverings
Construction details concealed by finishes
Insulation installed during previous renovation works
Hidden heating system components
Rather than guessing, assessors must follow the assumptions set out within the approved methodology.
Does "Assumed" Mean the Assessor Didn't Look?
No.
The assessor will inspect all accessible areas of the property and collect evidence wherever possible.
However, if a feature cannot be seen or supported by suitable evidence, the assessor must apply the appropriate RdSAP assumption.
The assessor is not guessing; they are following the approved EPC methodology.
This ensures consistency across all EPC assessments and helps ensure that every property is assessed using the same nationally recognised rules.
Can Assumptions Affect My EPC Rating?
Yes.
In some cases, an assumption may result in a lower energy performance than would be achieved if supporting evidence were available.
For example, if cavity wall insulation has been installed but there is no visible evidence and no supporting documentation, the assessor may be unable to record the insulation and may have to apply a default assumption instead.
This can affect the final EPC rating.
What Evidence Can Be Used?
Examples of acceptable supporting evidence may include:
Building Control completion certificates
Installation certificates
Guarantees and warranties
Photographs taken during building works
Documentation from installers
New-build specifications
Providing suitable evidence can sometimes enable a more accurate assessment of the property's energy performance.
Why Doesn't the Assessor Just Take My Word For It?
The EPC methodology requires assessors to rely on verifiable evidence.
Accredited assessors are subject to quality assurance procedures and independent audits. For this reason, they must be able to demonstrate how information recorded within the EPC has been verified.
Without supporting evidence, the assessor may be required to apply a standard assumption.
Common Examples of EPC Assumptions
The EPC may include assumptions relating to:
Wall insulation
Floor insulation
Roof insulation
Hot water cylinder insulation
Heating controls
Property construction details
Renewable energy installations where documentation is unavailable
Can an EPC Be Updated If Evidence Is Found Later?
In some circumstances, yes.
If suitable evidence becomes available after an assessment has been completed, it may be possible to review the information and determine whether a revised EPC is appropriate.
Property owners should contact the assessor who produced the EPC to discuss the available evidence.
How Can I Help Ensure My EPC Is Accurate?
Before the assessment, it can be helpful to gather any documentation relating to:
Insulation improvements
Boiler installations
Heating upgrades
Renewable energy systems
Building extensions or alterations
Providing supporting evidence at the time of the assessment may help ensure that the property is assessed as accurately as possible.
How A1 Home Inspectors Can Help
At A1 Home Inspectors, we follow the approved EPC methodology and record evidence wherever possible.
If an assumption is required, it will be applied in accordance with the assessment rules and not as a matter of personal opinion.
If you have documentation relating to insulation, heating systems, renewable energy technologies, or other energy efficiency improvements, providing it before the assessment may help ensure the most accurate EPC rating possible.
Have questions about assumptions within your EPC? Contact A1 Home Inspectors today and speak with one of our assessors.
Official Guidance
EPC assessments are carried out using approved methodologies that include prescribed assumptions where information cannot be verified. Property owners should refer to the latest Government guidance and EPC regulations for further information.
Disclaimer
The information provided on this page is for general guidance only. EPC assessments are carried out using approved methodologies and evidence requirements in force at the time of inspection. Where information cannot be verified, assessors may be required to apply assumptions in accordance with the relevant assessment rules. The application of assumptions does not necessarily indicate an error in the assessment.
