When it comes to Energy Performance Certificate (EPC) ratings, a property’s design plays a critical role. Two of the most influential design factors are building orientation and window placement. Both determine how much natural light, solar gain, and ventilation a home benefits from—factors that can significantly influence energy efficiency scores.

1. Why Building Orientation Matters for EPC

The direction a property faces impacts how much solar energy it naturally gains throughout the year.

  • South-facing homes typically receive more sunlight, reducing heating demand in winter.

  • North-facing properties may require more artificial lighting and heating.

  • East- and west-facing orientations can lead to overheating risks during summer months.

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2. The Impact of Window Placement

Windows directly affect EPC ratings through their influence on:

  • Thermal performance – poor glazing can increase heat loss.

  • Solar gain – strategically placed windows can capture free heat from the sun.

  • Natural lighting – well-placed windows reduce the need for artificial lighting during the day.

Homes with excessive or poorly insulated glazing, however, may suffer reduced EPC scores due to heat loss.

3. Optimising Orientation and Windows for Higher EPC Scores

Homeowners and developers can improve EPC outcomes by:

  • Installing high-performance glazing such as double, triple, or Low-E glass.

  • Using solar shading devices to prevent overheating in summer.

  • Designing window-to-wall ratios that balance natural light with insulation needs.

  • Leveraging zoned heating and cooling to manage varied solar exposure.

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4. EPC Challenges in Existing Homes

Older homes may not have been designed with energy efficiency in mind. Retrofitting solutions include:

  • Adding secondary glazing to improve insulation.

  • Installing internal or external blinds and louvres.

  • Enhancing roof and wall insulation to balance heat gain and loss.

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5. Professional EPC Assessment

A qualified EPC assessor will consider:

  • How building orientation impacts heating and lighting demand.

  • The type and performance of windows.

  • Opportunities to improve efficiency without compromising comfort.

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Conclusion

Building orientation and window placement are major drivers of EPC scores. South-facing homes with efficient glazing can achieve strong energy ratings, while poorly designed window layouts or excessive glazing may reduce scores. With careful design or targeted retrofits, homeowners can balance natural light, solar gain, and insulation to maximise both comfort and EPC performance.