Ever noticed your EPC certificate lists vague phrases like “assumed,” “unknown,” or “defaulted” in key areas such as wall types, insulation, or heating controls?
These EPC data gaps aren’t just technical oversights—they can significantly lower your property’s rating, mislead buyers and tenants, and cost you in legal compliance or mortgage negotiations.
In this article, we’ll explore:
Why EPC data gaps happen
How missing inputs affect your EPC rating
What you can do to fix data gaps and improve your certificate accuracy
What Are EPC Data Gaps?
EPC data gaps occur when the assessor:
Cannot access or verify specific construction details
Is not provided with adequate documentation for installed upgrades
Encounters parts of the property that are physically inaccessible during inspection
➡️ When this happens, default values (usually worst-case assumptions) are applied to the missing data, dragging down the overall EPC score.
➡️ Learn how EPCrate identifies and corrects defaulted EPC data.
Common Areas Where EPC Data Gaps Occur
| Data Field | Typical Gap Cause | Default Penalty |
|---|---|---|
| Wall Type & Insulation | Inability to verify cavity or solid wall insulation | Defaulted to “uninsulated” |
| Roof Insulation Thickness | Loft areas inaccessible or boarded over | Defaulted to minimal insulation |
| Floor Construction & Insulation | Lack of underfloor access | Defaults to uninsulated |
| Window Glazing Specification | No manufacturer labels or documents | Defaults to basic single glazing |
| Heating System Controls | Complex or undocumented control systems | Defaults to “basic programmer & thermostat only” |
| Air Tightness & Ventilation | Absence of air permeability test results | Assumed high air leakage |
Why Do These Data Gaps Occur?
1. Lack of Documentation
If you can’t provide:
Insulation certificates
Heating upgrade invoices
Product specification sheets
the assessor is forced to default that component to the least efficient option.
2. Physical Access Restrictions
Lofts, basements, or service ducts may be:
Boarded up
Inaccessible due to safety concerns
Locked or sealed off
No access = no verification = default value applied.
3. Older or Converted Properties
Older homes, barn conversions, and flats above shops often lack:
Modern construction records
Clearly identifiable building fabric
These complexities increase the likelihood of defaults unless meticulously assessed.
➡️ Check how EPCrate handles heritage and complex properties.
4. Time-Pressed or Inexperienced Assessors
If an assessor is:
Rushing the survey
Unfamiliar with handling non-standard properties
they may default ambiguous areas rather than investigate thoroughly.
The Impact of EPC Data Gaps on Your Rating
| Scenario | EPC Band Without Gaps | EPC Band With Defaults |
|---|---|---|
| Modern flat with verified insulation | Band B | Band C or D |
| 1930s semi-detached with documented retrofits | Band C | Band D |
| Listed building with undocumented upgrades | Band D | Band E or F |
Real-World Consequences:
Lower EPC bands impact property valuations
Mortgage lenders may penalise inefficient ratings
MEES non-compliance fines if rental properties default below Band E
Missed opportunities for green financing products
➡️ Correct EPC data gaps to unlock better mortgage and rental prospects.
How to Fix EPC Data Gaps & Improve Your Certificate
1. Gather Documentation Before Assessment
Prepare:
Insulation installation certificates
Heating system manuals and commissioning records
Product specifications for glazing and ventilation systems
Air tightness test results (if available)
2. Ensure Full Access to Survey Areas
Unblock loft hatches and service panels
Provide keys or access to basements, crawl spaces, etc.
Clear obstacles that might hinder a thorough inspection
3. Hire an Experienced EPC Assessor
At EPCrate, we specialise in:
Minimising default assumptions through comprehensive inspections
Using advanced tools (e.g., endoscopes, thermal imaging) where access is limited
Advising clients on how to gather missing documentation pre-survey
➡️ Book a data-gap-free EPC assessment today.
What If Documentation is Lost or Unavailable?
If original documents are missing:
Alternative proof methods (photos, invoices, installer contacts) may still suffice
A deeper on-site inspection can sometimes verify construction details
If certain upgrades are visible but undocumented, assessors can apply “as-built” evidence credits
➡️ Ask EPCrate about alternative verification strategies.
Conclusion: Don’t Let Data Gaps Sabotage Your EPC Rating
An EPC certificate full of defaulted “unknowns” isn’t just a technicality—it’s a direct hit on your property’s marketability, legal compliance, and financial flexibility.
By proactively addressing EPC data gaps, you can ensure your rating reflects your property’s true efficiency.
With EPCrate’s data-accuracy-driven assessments, we make sure no efficiency upgrade goes unrecognised.
➡️ Book a comprehensive EPC assessment to eliminate data gaps
➡️ Contact us for documentation advice and EPC corrections
