Roof windows and skylights are popular features in modern homes, providing natural light, ventilation, and an open feel. However, they can significantly impact a property’s Energy Performance Certificate (EPC) rating. Understanding how these features influence EPC performance is essential for homeowners, landlords, and property developers.
How Roof Windows and Skylights Affect EPC Ratings
1. Heat Loss and Thermal Efficiency
Roof windows generally have lower insulation than solid roofing materials. This can increase heat loss, raising the building’s U-value—a key factor in EPC assessments.
Glazing type: Double or triple glazing reduces heat loss compared to single glazing.
Frame materials: Thermally broken frames improve insulation.
Size and quantity: Larger or numerous skylights can lead to greater heat loss.
2. Solar Gain
Skylights can also provide passive solar heating, reducing the need for artificial heating during colder months.
Orientation matters: South-facing windows maximize solar gain in the Northern Hemisphere.
Glazing coatings: Low-emissivity (Low-E) coatings control heat gain while minimizing heat loss.
Shading solutions: External blinds or shades prevent overheating in summer.
3. Ventilation and Cooling
Operable roof windows and skylights improve natural ventilation, reducing reliance on mechanical cooling. This can have a positive effect on energy efficiency and EPC performance.
4. Installation Quality
Even high-performance skylights can lower EPC ratings if installed poorly. Air leaks, improper sealing, and lack of insulation integration all contribute to heat loss.
Practical Tips to Maintain EPC Performance with Roof Windows
Choose high-performance glazing – Double or triple-glazed units with Low-E coatings.
Ensure proper insulation – Surrounding roof areas should be well-insulated.
Optimize size and orientation – Balance natural light and solar gain for energy efficiency.
Consider shading solutions – Blinds, overhangs, or external shades.
Regular maintenance – Check seals and glazing to prevent drafts.
Internal Resources for EPC Guidance
For more detailed guidance on maintaining and improving your EPC rating with roof windows and other features, visit:
Contact Us for a consultation with our experts.
About Us to learn more about Urgent EPC services.
Conclusion
Roof windows and skylights enhance natural lighting, ventilation, and home aesthetics but have a measurable impact on EPC performance. Careful selection, proper installation, and ongoing maintenance are essential to maintain energy efficiency and improve EPC ratings.
