It’s a surprising but common trend: in a newly built apartment block, top-floor flats often receive lower EPC ratings than identical units below. This can be frustrating for buyers, landlords, and developers who assume that all flats in the same building should perform the same on energy efficiency.

But the EPC (Energy Performance Certificate) system—especially under the SAP (Standard Assessment Procedure) model—has built-in limitations that can penalise upper-floor properties, even when their real-world performance may be equal or better.

Let’s dive into why this happens—and what can be done about it.

🔍 Understanding the EPC Assessment for Flats

EPCs for residential buildings in the UK are calculated using SAP, a theoretical model that estimates:

  • Energy consumption

  • Heating demand

  • Carbon emissions

  • Running costs based on standardised conditions

The SAP model treats each flat as a standalone unit, accounting for its orientation, floor area, insulation, heating type, and exposure to external elements. This is where top-floor flats get caught out.

Learn more about our EPC approach here: EPC Assessors London

🧱 Why Top-Floor Flats Score Lower: 4 Technical Reasons

1. Increased Heat Loss Through the Roof

Unlike middle-floor flats, top-floor units share a ceiling with the roof, which is exposed to outdoor temperatures. Even with high-quality insulation, SAP assumes a greater heat-loss area than for a flat with another unit above.

🔸 Bottom and middle flats benefit from “heated neighbours” above and below, which SAP counts positively.

2. Reduced Thermal Buffering

Internal flats have at least 3 or 4 shared walls or floors/ceilings, meaning they lose less heat overall. In contrast, top-floor flats often have:

  • External walls on 2–3 sides

  • An unheated roof space or direct roof exposure

  • Possibly a cold stairwell or lift shaft on one side

This adds to the external heat-loss perimeter, reducing the SAP score.

3. Flat-Specific Heating Loads

Even if the building uses a central heating system, each flat’s individual heat demand is assessed separately. A top-floor flat may:

  • Need more energy to stay warm

  • Score lower despite using the same system as others

This is especially evident in buildings without underfloor insulation between flats.

4. SAP Doesn’t Reward Passive Heat Gains Properly

Top-floor flats often enjoy better sunlight exposure and gain more natural warmth in winter. But SAP doesn’t model dynamic solar gain effectively—it uses static window factors, so that extra performance isn’t credited fully.

⚠️ The Real-World Impact

This scoring discrepancy creates issues such as:

  • Lower property values or reduced buyer interest due to a B-rating instead of an A

  • MEES compliance problems for landlords renting out top-floor units

  • Confusion when identical layouts show different EPCs

And in many cases, tenants in top-floor flats report lower heating bills, suggesting the model doesn’t reflect reality.

Looking for a fair EPC reassessment? Book with us now.

🧾 What Can Developers and Owners Do?

✅ Work with Experienced EPC Assessors

Our assessors understand how to model apartment buildings for maximum fairness—especially in SAP 10.2 and post-2021 building regs. See how we help: About Us

✅ Provide Accurate Construction Data

  • Roof insulation thickness and U-values

  • Air tightness test results

  • Floor/ceiling insulation between units

Better data leads to better scores.

✅ Consider Roof-Level Enhancements

For developers:

  • Improve flat roof insulation (especially cold deck roofs)

  • Use warm roofs or green roofs

  • Add MVHR or PV systems to top-floor units

These can offset the EPC penalty and boost overall performance.

📉 Final Thoughts: EPC Blind Spots in Flat Blocks

The EPC model is useful but not always fair—especially for top-floor flats in otherwise efficient new builds. Until the SAP methodology better reflects dynamic heat gains and real-life performance, upper-level properties may continue to be underrated.

Whether you’re a buyer, landlord, or developer, understanding these EPC pitfalls can help you make better design decisions, defend your property’s value, or plan upgrades wisely.

📅 Ready to check your flat’s EPC or explore improvement options?
🔍 Book your EPC today
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