Most homeowners are shocked when their Energy Performance Certificate (EPC) rating comes back lower than expected. While some issues are obvious — like old boilers or lack of insulation — many score-dropping factors are subtle, hidden, and easy to overlook. EPC assessors follow a strict methodology, and even small inefficiencies can significantly impact your rating.

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1. Poor or Missing Insulation (The #1 EPC Score Killer)

Nothing lowers an EPC rating faster than inadequate insulation. Assessors check insulation depth, coverage, and material quality. Common problems include:

• Loft insulation below 270mm

• Missing cavity wall insulation

• Solid walls with no insulation layer

• Gaps or patchy insulation from previous work

Without proof or visible insulation, assessors must assume the worst-case scenario.

To learn more about how EPC assessments work, visit our About page:
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2. Outdated or Inefficient Heating Systems

Your heating system contributes heavily to your EPC score. Assessors quickly flag:

• Non-condensing boilers

• Old radiators with no TRVs

• Manual thermostats with no zone controls

• Immersion heaters without insulation

Upgrading your boiler or installing smart heating controls can dramatically increase your score.

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3. Single Glazing or Poor Window Seals

Even if the rest of your home is efficient, old or poorly sealed windows heavily reduce your rating. Assessors look for:

• Single glazed windows

• Failed double-glazing units (condensation inside panes)

• Draughty frames

• No trickle vents

Switching to energy-efficient glazing can boost comfort and your EPC score.

4. Inefficient Lighting Throughout the Home

Lighting may seem minor, but if more than half your home uses halogen or incandescent bulbs, the EPC score drops noticeably.

LED lighting is one of the cheapest, fastest EPC improvements.

5. Uninsulated Hot Water Cylinders & Old Pipework

Another major issue flagged immediately:

• Bare hot water cylinders

• Cylinders with thin or damaged insulation jackets

• Exposed, uninsulated pipework

These cause heat loss, drive energy bills up, and reduce EPC efficiency.

6. Lack of Documentation for Upgrades

One of the most common (and frustrating) reasons for a low EPC score:

Homeowners forget to show the assessor proof of improvements.

This includes:

• Loft insulation certificates

• Boiler installation documentation

• Solar panel system details

• Window or door replacement invoices

Without proof, assessors must default to standard assumptions — often lower than reality.

7. Air Leakage and Draught Problems

Assessors routinely flag unseen air leaks that allow heat to escape:

• Gaps around doors and windows

• Cracks in walls

• Draughty fireplaces

• Uninsulated loft hatches

Draught-proofing is a low-cost solution that provides noticeable EPC improvements.

8. Old Construction Features in Older Homes

Older homes often lose points because they contain original features that aren’t energy-efficient:

• Solid walls

• Suspended timber floors

• Uninsulated roofs

• Inefficient chimneys

While upgrading these can be expensive, even partial improvements can boost a property’s rating.

How to Avoid a Low EPC Rating

To ensure your score reflects your home’s true energy efficiency:

1. Prepare documentation

2. Fix small inefficiencies like draughts, lighting, and insulation gaps

3. Upgrade heating controls

4. Consult with a professional assessor before your EPC appointment

If you’re ready to schedule your assessment, book here:
https://epcrate.co.uk/booking/

For any questions or guidance, contact us directly:
https://epcrate.co.uk/contact-us-epc-services-london/

Conclusion

A low EPC score rarely comes from one major fault — it’s usually a combination of overlooked issues. Assessors immediately flag missing insulation, old heating systems, poor glazing, and lack of documentation. Addressing these areas ahead of your assessment can significantly increase your EPC rating, reduce energy bills, and improve your property’s value.

For expert EPC assessments, reliable guidance, and fast bookings, use the links below:
About Us: https://epcrate.co.uk/about-us-epc-company-london/
Booking: https://epcrate.co.uk/booking/
Pricing: https://epcrate.co.uk/pricing/
Services (EPC Assessors London): https://epcrate.co.uk/services-epc-assessors-london/
Contact Us: https://epcrate.co.uk/contact-us-epc-services-london/

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Does Insulation Always Improve EPC? The Truth About Common Upgrades

Insulation is usually the first upgrade homeowners think of when trying to improve their EPC rating — and for good reason. Insulation reduces heat loss, lowers energy bills, and can significantly boost a property’s efficiency.

But here’s the truth most people don’t realise: insulation doesn’t always improve your EPC score, and in some cases, it may not affect the rating at all. Your results depend on the type of insulation, the property’s age, what already exists, and whether documentation is available.

Before spending money on insulation upgrades, it’s important to understand how EPC software actually evaluates your home. For expert help, explore our EPC assessor services:
https://epcrate.co.uk/services-epc-assessors-london/

1. When Insulation WILL Increase Your EPC Rating

Insulation boosts your EPC score only when it meaningfully reduces heat loss. The biggest improvements come from:

✔ Loft / Roof Insulation

Properties lose up to 25% of heat through the roof.
Increasing insulation depth to 270mm or more creates measurable, guaranteed gains.

✔ Cavity Wall Insulation

For homes with unfilled cavity walls, insulation can dramatically improve the EPC rating.

✔ Floor Insulation

Insulating suspended timber floors adds a strong efficiency boost, especially in older homes.

✔ Pipework and Hot Water Tank Insulation

Cylinder jackets and pipe insulation also improve your hot water system efficiency.

To learn more about how EPC assessors evaluate insulation, see our About page:
https://epcrate.co.uk/about-us-epc-company-london/

2. When Insulation Might NOT Improve Your EPC Rating

Many homeowners are surprised to learn that some insulation upgrades have little to no effect on their EPC. This happens when:

✖ Your Property Already Has Enough Insulation

If loft insulation is already around 250–270mm, adding more won’t improve the score.

✖ The EPC Software Uses Assumptions

If insulation cannot be seen or documented, assessors must assume standard defaults.
This can eliminate the expected rating boost.

✖ Your Home Has Solid Walls

Solid wall insulation does improve EPC — but only if:

• Installed correctly

• Documented

• Clearly visible

Costly improvements like internal/external wall insulation don’t always deliver as much EPC gain as homeowners expect.

✖ The Insulation Is Poorly Installed

Gaps, damp insulation, or partial coverage stop EPC software from marking it as “effective.”

✖ Other Areas of the Home Are Weaker

Even if you insulate the loft, a poor boiler or single glazing may overshadow the improvement.

3. The Insulation Upgrade Most Homeowners Overrate

Loft Top-Ups Beyond 270mm

Once loft insulation passes a certain depth, EPC software stops giving extra credit.
So adding an extra layer from 300mm to 400mm makes no difference.

4. Upgrades That Often Improve EPC MORE Than Insulation

If your insulation is already adequate, these upgrades may boost EPC faster:

• Replacing an old boiler with a condensing model

• Adding smart heating controls

• Installing thermostatic radiator valves (TRVs)

• Switching to low-energy LED lighting

• Upgrading to double or triple glazing

• Adding renewable technology such as solar PV

Check EPC pricing and compare upgrade options:
https://epcrate.co.uk/pricing/

5. The Biggest EPC Mistake Homeowners Make: No Documentation

Even if your home is well insulated, your EPC will not improve unless you provide proof such as:

• Loft insulation certificates

• Cavity or solid wall insulation reports

• Installer invoices

• Photographs taken during installation

Without evidence, assessors must assume the insulation is missing or inadequate.

To ensure your assessor records all improvements accurately, book your EPC assessment early:
https://epcrate.co.uk/booking/

Conclusion

Insulation is one of the most powerful EPC upgrades — but it doesn’t automatically increase your rating. EPC improvement depends on:

• What insulation already exists

• Whether installation is visible and documented

• Other weak areas in the property

• The type and condition of the insulation

Before investing in upgrades, consult a qualified EPC assessor who can identify exactly where your home is losing points.

Email :info@epcrate.co.uk

Phone:020 34884142