When properties fail their Energy Performance Certificate (EPC) assessment, many owners immediately think of outdated boilers or insufficient insulation. However, a frequently overlooked factor is poorly sealed doors and windows. These small gaps and drafts can have a surprisingly large impact on your EPC score, potentially dragging a property below the required compliance thresholds.
In this article, we explore how air leakage from windows and doors affects EPC outcomes, and practical steps you can take to address this hidden efficiency culprit.
If you’re concerned about how your property’s air leakage may affect its EPC rating, visit our Services page for tailored assessment solutions.
1. How EPC Assessments Evaluate Draught-Proofing
The Reduced Data Standard Assessment Procedure (RdSAP) — used for domestic EPCs — considers the air-tightness of a building envelope. While specific air permeability testing is not typically conducted for domestic properties, visual inspections play a critical role. Assessors examine:
Door and window seals.
Presence of draught-proofing strips.
Gaps around frames and sills.
Chimneys, vents, and loft hatches.
If obvious gaps or missing seals are observed, the assessor will assume higher air leakage rates, which negatively affect the EPC score. To ensure your draught-proofing measures are properly documented, book an EPC inspection with our experienced assessors.
2. Why Draughty Windows and Doors Lower EPC Ratings
Air leaks result in:
Increased Heat Loss: Warm air escapes in winter, forcing heating systems to work harder.
Higher Energy Consumption: Inefficient thermal performance increases utility bills.
Poor Thermal Comfort: Cold spots and drafts impact occupant comfort.
These factors are translated into the EPC software model, reducing the property’s overall energy efficiency rating.
3. Common Air Leakage Points EPC Assessors Check
Old Wooden Sash Windows: Prone to gaps due to age and movement.
UPVC Frames with Damaged Seals: Worn rubber gaskets and misaligned hinges.
Front and Back Doors: Poor threshold sealing and letterbox drafts.
French and Bi-Fold Doors: Misaligned locking mechanisms causing frame gaps.
Loft Hatches and Service Ducts: Often overlooked, but major leakage points.
During an assessment, we conduct a thorough inspection of these areas. Learn about our detailed approach on the About Us page.
4. Simple Draught-Proofing Solutions That Boost EPC Ratings
Install Draught-Excluder Strips: Self-adhesive foam or brush strips around frames.
Upgrade Door Thresholds: Fit weather bars or threshold seals.
Seal Letterboxes and Keyholes: Use spring-loaded flaps or keyhole covers.
Repair or Replace Window Seals: Ensure rubber gaskets are intact and functional.
Secondary Glazing for Older Windows: Adds an additional air-tight layer.
These low-cost interventions can improve thermal efficiency noticeably and contribute positively to your EPC score.
5. Case Study: EPC Rating Improvement Through Draught-Proofing
A mid-terrace Victorian property in London recently upgraded from an E EPC rating to a D simply by:
Sealing gaps in sash windows.
Installing draught-proofing around external doors.
Adding secondary glazing to a large bay window.
These minor works, costing under £500, delivered sufficient efficiency gains to improve the EPC band — making the property compliant with MEES regulations for rentals.
For an accurate cost estimation and assessment, visit our Pricing page.
6. Homeowner Checklist: Preparing Doors and Windows for Your EPC Assessment
Inspect all external doors and windows for visible gaps.
Check for missing or worn rubber seals and replace where necessary.
Install draught-proofing strips if original joinery is retained.
Ensure letterboxes and keyholes are covered.
Document any draught-proofing improvements and provide to the EPC assessor.
Schedule a reassessment through our Booking page.
7. Why Draught-Proofing is One of the Best ROI EPC Upgrades
| Upgrade | Cost Range | EPC Impact |
|---|---|---|
| Draught-proofing Doors & Windows | £100 – £300 | 3-7 EPC points |
| Secondary Glazing Installation | £300 – £800 | Significant (especially for period properties) |
| Professional Air Tightness Survey | £250 – £400 | Supports EPC documentation |
Given the affordability and high return on EPC scoring, draught-proofing should be a priority for any property struggling to meet efficiency standards.
Conclusion
Poorly sealed doors and windows are a silent but significant contributor to EPC failures. Fortunately, rectifying these issues is often simple and cost-effective. With proper draught-proofing measures, property owners can prevent unnecessary heat loss, improve occupant comfort, and enhance their EPC rating — ensuring compliance with current regulations.
At EPCrate, we specialise in identifying and documenting all efficiency upgrades, including subtle measures like draught-proofing, to ensure your property achieves the highest possible EPC score. Schedule your EPC assessment today through our Booking page or reach out via our Contact page.
