How to make buildings more energy efficient with skylights?

This article explores how skylights influence energy efficiency in commercial buildings, the balance they create between natural light and thermal performance, and how they contribute to overall building sustainability goals.

The holistic approach to building design

Good building design requires a holistic approach to ensure good functionality of a building. During the design and decision process, aspects of indoor environmental quality and comfort, structural stability, weather protection, energy efficiency, security and safety should be considered. Achieving top performance in all these areas can be challenging and costly, with priorities varying based on the project. Therefore, it is a matter of delicate balance to choose the right product with the right set of characteristics for the right purpose. However, energy efficiency and sustainability are key, especially when selecting skylights.

In terms of glazing and energy efficiency, that balance means contributing to thermally efficient, airtight building fabric with the right area of glazed openings. The result is reduced electric lighting use, thanks to the availability of natural light, but at the same time avoiding excessive solar gains - as well as giving occupants a connection to the outside.

Skylights play a major role as basis for building performance assessments

This holistic approach is supported by whole-building assessment methods like BREEAM (Building Research Establishment Environmental Assessment Method), LEED (Leadership in Energy and Environmental Design), the DGNB (German Sustainable Building Council), and the Well Building Standard. They all emphasize the importance of daylight in enhancing occupant well-being and reducing energy consumption. By incorporating skylights, buildings can achieve higher daylight factors and better uniformity in light distribution, which are critical for meeting daylighting requirements of performance-based criteria and sustainability goals.

Industry trends in commercial daylighting

The commercial daylighting landscape continues to evolve with several notable trends:

• Integration with smart building systems
  Modern skylights can now connect with building automation systems, adjusting based on occupancy, time of day, and weather conditions.
  
  
• Net-zero building design
  As more organizations commit to carbon neutrality, skylights play a crucial role in reducing dependence on artificial lighting.
  
  
• Biophilic design principles
  The growing recognition of nature's influence on human wellbeing has positioned skylights as key elements in connecting indoor spaces with the natural environment.
  
  
• Resilient building strategies
  With increasing focus on building adaptability, skylights that offer passive cooling and natural ventilation contribute to overall building resilience.

The impact of daylight on energy use

Using daylight to its full potential can reduce, or even eliminate, the electricity demand for artificial lighting during the day. To reach this conclusion, VELUX investigated the effect of daylight on energy use in a building.

A scenario was modelled where a house had no windows and light levels had to be achieved with electric lighting only. Using electric lighting influences heating and cooling demand, so the energy use for lighting, cooling and heating was evaluated together.

The results showed that relying on electric lighting to provide lux levels equivalent to daylight resulted in an energy demand some five times greater than an equivalent house with well-designed glazing and no electric lighting.

Studies of office buildings have demonstrated similarly positive results. While they are more complex in terms of having unique occupancies, internal layouts and lighting controls (manual and automatic), and therefore less suited to a ‘definitive’ assessment, energy savings of 20 to 60% have been evidenced.

A real-world project: Copenhagen school's success with skylight replacement

The refurbishment of Peder Lykke School in Copenhagen highlights the role of skylights in boosting energy efficiency while enhancing the learning environment. The project involved replacing 68 rooflights with 184 modular, double-unit skylights, providing natural daylight and comfort ventilation throughout the building.

The skylights reduce the need for artificial lighting, cutting electricity consumption, and improve air quality by supporting passive ventilation. Automated features like rain sensors optimize energy efficiency and maintain comfort without heavy reliance on HVAC systems.

With minimal disruption to learning, the installation was completed in just one weekend, and the school now accommodates 700 students. This upgrade not only saves energy but also enhances well-being and productivity, ensuring daylight and fresh air are part of everyday school life.

The unique benefits of roof glazing

Roof windows and skylights:

• Deliver double the daylight compared to façade (vertical) windows of the same surface area.
• Achieve required illuminance levels with smaller glazing areas.
• Provide better light distribution in rooms.

Using daylight modelling to help refine the requirements means the balance of façade windows and roof windows can be part of initial design concepts, addressing any overheating concerns and keeping electric lighting demand to a minimum. When whole-building performance is eventually addressed, these benefits will contribute to a positive outcome.

Understanding skylight thermal performance

Thermal performance is crucial to a building's energy efficiency, indoor comfort. High-performance glazing plays a key role in this by helping to regulate heat flow, making buildings more sustainable. Low-emissivity (Low-E) coatings reduce heat loss in winter and minimize heat gain in summer, contributing to better energy efficiency throughout the year. Additionally, advanced technologies like electrochromic and solar cell glazing offer further improvements in building performance, enhancing both energy conservation and sustainability.

What is the U-value?

The U-value measures how well a building component, like a window, insulates against heat transfer. A lower U-value indicates better insulation, meaning less heat escapes in winter and less heat enters in summer. For windows, the U-value considers factors like the type of glazing, the frame material, and any gaps or bridges that might allow heat to pass through. By improving these elements, such as using insulating gases between the glass panes, buildings can reduce energy loss and improve overall thermal performance. Read more about U-values.

Skylight solutions for every building need

VELUX Commercial Modular Rooflights and Modular Skylights offer a versatile and high-performance solution for bringing natural light into buildings. These products feature double glazed roof panels with low emissivity coatings, enhancing energy efficiency by minimizing heat loss. Triple glazing options are also available for even greater thermal performance.

In addition to these glass roof systems, dome rooflights provide another excellent option for enhancing energy efficiency in buildings. Dome rooflights are typically made from acrylic or polycarbonate materials. They feature a multi-wall construction with air gaps that provide additional insulation, significantly reducing heat transfer compared to single-skin alternatives.

At Messe Karlsruhe dome rooflights with electric SHEV enhance fire safety and thermal insulation

Both glass skylights and dome rooflights come with a variety of coating options specifically designed to optimize the levels of solar heat gain, sun protection, and light transmittance. For instance, some coatings can minimize the amount of solar heat entering the building, which is particularly beneficial in warmer climates. Others can enhance light transmittance, ensuring that spaces are well lit with natural daylight while still providing adequate sun protection.

The choice between glass skylights and dome rooflights often depends on specific project requirements:

• Glass solutions typically offer superior thermal performance (lower U-values) and clarity, making them ideal for occupied spaces where aesthetics and energy efficiency are primary concerns.
• Plastic dome rooflights provide lightweight construction and generally lower initial cost. When made with high-quality compounds and advanced features, they also provide safety and protection from UV and harsh weather conditions, ensuring a long service life for many applications. These rooflights are ideal for projects where thermal performance requirements are less stringent than what insulating glass provides.

When properly specified and installed, both solutions contribute significantly to reducing a building's carbon footprint by decreasing reliance on artificial lighting and potentially lowering heating costs through passive solar gain in colder months.

The human factor: Occupant well-being benefits

While energy efficiency provides clear financial returns, the impact of natural daylight on human performance may represent an even greater value proposition. Research consistently shows that exposure to natural daylight improves productivity, health, cognitive function, mood and satisfaction. For businesses, these benefits translate to improved workforce performance, reduced absenteeism, and greater employee retention.

Aligning with the Healthy Buildings framework

The VELUX Healthy Buildings Barometer 2024 introduces a comprehensive framework for healthy buildings, consisting of five key dimensions:

1. Improving mental and physical health
   Skylights directly contribute to this dimension by providing natural daylight, which has been proven to enhance both physical and mental wellbeing.
2. Designed for human needs
   Strategic skylight placement creates spaces that respond to human biological needs for natural light and connection to the outdoors.
3. Sustainably built and managed
   Energy-efficient skylights reduce dependence on artificial lighting, lowering carbon emissions and operational costs.
4. Resilient and adaptive
   Operable skylights provide natural ventilation, reducing cooling loads while adapting to changing external conditions.
5. Empowering people
   Modern skylight solutions with user controls allow occupants to take charge of their environment, enhancing satisfaction and engagement.

By investing in high-quality skylight solutions, building owners can address multiple dimensions of this framework simultaneously, creating spaces that are not just energy-efficient, but truly healthy for their occupants.

Bespoke skylight solutions tailored to suit any space, shape, or design vision

Conclusion: The future is bright

As building energy codes become more stringent and organizations increasingly prioritize sustainability, skylights will continue to play a crucial role in commercial building design. Their unique ability to deliver abundant natural light while managing thermal performance positions them as essential components in the energy-efficient buildings of tomorrow.

By taking a holistic approach that considers both building energy performance and human factors, building owners and designers can leverage skylights to create spaces that are not only more sustainable but also more productive, comfortable, and appealing to occupants.

Ready to transform your commercial building with energy-efficient skylights? Contact our VELUX Commercial experts for a customized daylighting solution that will reduce your energy costs while enhancing occupant wellbeing.

Sources:

1. Guide to Daylighting and EN 17037
2. VELUX, "Window systems," Daylight, Energy and Indoor Climate Basic Book
3. VELUX, 2024, Healthy Buildings Barometer