Draught proofing is one of the most affordable and effective ways to make your home feel warmer and reduce energy bills. Yet many property owners are surprised to find that EPC ratings don’t always improve after they’ve sealed windows, added letterbox covers, or blocked chimney flues.
So, why doesn’t this seemingly logical upgrade always translate to a better Energy Performance Certificate (EPC) score?
In this article, we’ll uncover the reasons why draught proofing may not be fully recognised in your EPC—and what you can do about it.
🧐 What Is Draught Proofing?
Draught proofing involves sealing unintended gaps in a building that allow cold air in and warm air out. These gaps are not part of the controlled ventilation system (like extractor fans or trickle vents) and typically occur around:
Windows and doors
Letterboxes and keyholes
Chimneys and loft hatches
Floorboards and skirting boards
Pipe and cable penetrations
Draught-proofing reduces heat loss and improves thermal comfort, often at a low cost. So why isn’t it always factored into your EPC?
🔍 EPC Methodology: The Key Reason Draught Proofing May Be Overlooked
The EPC for existing homes is calculated using RdSAP (Reduced Data Standard Assessment Procedure). This method makes generalised assumptions based on:
Property age
Construction type
Visual evidence only (no intrusive inspections)
Standardised default values when data is missing
❗ Here’s the catch:
RdSAP does not directly include draught proofing as a separate data input.
Unless draught proofing is part of a broader airtightness strategy (like in new builds tested via SAP), its impact is not formally captured in the EPC software.
💬 What the Assessor Sees vs What You’ve Done
An EPC assessor is only allowed to record what they can physically verify at the time of inspection. This means:
If draught-proofing strips are hidden or subtle, they may go unrecorded.
Sealed floorboards or pipe gaps behind skirting may not be visible.
Chimney balloons or interior flue blockers might be missed unless clearly pointed out.
Even if present, these improvements might be lumped into default assumptions for air leakage based on the building’s construction age.
🔎 For example: A 1930s semi-detached house is assumed to have high air permeability unless there’s substantial and visible evidence to prove otherwise.
📉 EPC Limitations: Default Values Trump Real Upgrades
RdSAP uses standardised assumptions about air infiltration for properties built in different eras. For instance:
| Property Age | Default Air Leakage Rating | Assumed Draught Level |
|---|---|---|
| Victorian (pre-1919) | High | Leaky/draughty |
| 1980s | Moderate | Mixed |
| Post-2012 | Low | Well-sealed |
Even if you’ve added excellent draught proofing to an older home, the model may not adjust unless supported by extensive visible proof or part of a whole-building retrofit.
🏗️ New Builds vs Existing Homes: A Different Approach
New builds and major refurbishments follow the full SAP methodology, which includes:
Air permeability testing (blower door test)
Detailed recording of airtightness strategies
In these cases, draught proofing efforts can significantly influence the EPC because they’re integrated into the design, build, and test process.
For older homes assessed via RdSAP? The system just isn’t as precise.
🧠 So, Is Draught Proofing a Waste of Time?
Absolutely not. Even if it doesn’t boost your EPC score, draught proofing still:
Lowers your heating bills
Reduces your carbon footprint
Improves indoor comfort
Makes your home more attractive to buyers or tenants
Plus, when combined with other upgrades—like loft insulation, LED lighting, or efficient heating controls—you might see a cumulative EPC uplift.
💡 Pro Tips to Maximise Recognition in Your EPC
Point it out during the assessment.
Tell your assessor what you’ve draught-proofed and where.
Show visible products like door seals or chimney blockers.
Pair with other recognised upgrades.
Add loft insulation or LED lights for measurable gains.
Use professional installation if possible.
Certified work, especially under a retrofit scheme, may hold more weight.
Consider a blower door test.
For major retrofits, this may quantify airtightness and shift your EPC rating more accurately.
🏠 For Landlords: Does Draught Proofing Help MEES Compliance?
The Minimum Energy Efficiency Standards (MEES) require most rented homes to have an EPC rating of E or higher. While draught proofing alone might not be enough to lift a low-rated F or G property to compliance, it’s still:
Cost-effective
A good first step before pricier upgrades
Useful for tenant comfort and lower utility costs
🔚 Final Thoughts: The Silent Hero of Home Efficiency
Draught proofing might not be the star of your EPC certificate, but it’s a low-cost powerhouse for practical energy savings. While RdSAP may overlook it, the real-world benefits are impossible to ignore.
Need help navigating EPC improvements?
At EPCrate.co.uk, we guide you through both visible and invisible upgrades that can boost your energy rating—and your home’s efficiency.
✅ Book a qualified assessor
✅ Get tailored EPC improvement advice
✅ Maximise every opportunity for a better score
