Windows are more than just openings for light and views—they play a crucial role in a building’s energy efficiency. When it comes to Energy Performance Certificates (EPCs), the type of windows and glazing used can significantly affect a property’s energy rating. Understanding how different window types and glazing options influence EPC outcomes can help homeowners and landlords make smart decisions to improve their property’s energy performance.

Why Windows Matter in EPC Assessments

Windows are one of the main points where heat can be lost or gained. They affect:

  • Heat retention in winter

  • Solar heat gain in summer

  • Air leakage and drafts

  • Natural daylight penetration

All these factors are considered during an EPC assessment and directly impact the energy rating.

Common Window Types and Their EPC Impact

1. Single-Glazed Windows

  • Least energy efficient due to high heat loss.

  • Typically lower EPC scores unless combined with other efficiency measures.

2. Double-Glazed Windows

  • The most common upgrade for better thermal performance.

  • Helps reduce heat loss and improve EPC ratings.

  • Quality of spacer bars and gas fills (argon, krypton) also matters.

3. Triple-Glazed Windows

  • Offer superior insulation and can significantly boost EPC scores.

  • Particularly beneficial in colder climates or for new-build properties.

4. Secondary Glazing

  • An effective retrofit option to improve thermal performance without full window replacement.

  • Can help lift EPC ratings in older buildings.

Types of Glazing and Their Effect on EPC Scores

  • Low-E (Low Emissivity) Coatings: Reflect heat back into the room, reducing heat loss. Improves EPC outcomes.

  • Gas Fills (Argon, Krypton): These inert gases between panes reduce heat transfer. Argon is common; krypton performs better but is costlier.

  • Warm Edge Spacer Bars: Reduce heat loss at the edges of the glass, improving thermal performance.

  • Tinted or Reflective Glazing: Can reduce solar gain in hot climates, lowering cooling demand.

Other Window Features Affecting EPC Ratings

  • Frame Materials: uPVC, timber, and aluminum frames have different insulating properties. Thermally broken aluminum frames perform better.

  • Air Tightness: Proper installation and sealing reduce drafts and improve EPC scores.

  • Window Size and Orientation: Larger windows may increase heat loss if not well insulated but can boost daylight, reducing lighting energy.

Tips to Improve EPC Scores Through Window Upgrades

  • Replace single glazing with double or triple glazing where feasible.

  • Opt for windows with Low-E coatings and quality gas fills.

  • Ensure professional installation to maximize airtightness.

  • Consider secondary glazing in heritage or listed buildings where replacements are restricted.

How EPCRate Supports Your EPC Improvement Journey

At EPCRate, our experienced EPC assessors in London evaluate all aspects of your windows and glazing during energy assessments. We provide tailored recommendations to help you enhance your property’s energy performance and meet regulatory requirements.

Explore our full range of EPC services or book your assessment today. Transparent pricing ensures no surprises.

Contact EPCRate for Expert EPC Assessments in London

For professional advice and accurate EPC ratings considering your window types and glazing, contact us via our contact page. Let EPCRate help you make informed energy efficiency decisions.

Windows are key to your property’s energy efficiency—optimize them with EPCRate, your trusted London EPC experts.