VELUX America Study Finds Skylights Offer Energy Efficiency to Single-family Homes

Homes that depend more on skylights in combination with vertical windows to provide adequate levels of daylight tend to be more energy efficient, according to a study commissioned by VELUX America.

“A Study of the Energy Impacts of Residential Skylights in Different Climates,” prepared by Group14 Engineering, used computer models based on a 1-story, open plan, single-family home modeled under code-compliant conditions of California’s Title 24 regulations (California Energy Commission, 2008), Residential Package D. The baseline-modeled home has a maximum 20 percent window-to-floor area (with no skylights) with windows evenly distributed on all facades to achieve an average daylight factor of 5 percent.

Researchers added skylights and adjusted the amount and configuration of vertical windows to test how the model would perform in different climate zones, while giving the living space sufficient daylight to allow lights to be switched off. The study explored the effects of these configurations on the utility bills generated by the model homes in Los Angeles and Napa, California, and then expanded the models to Boston, Chicago, Denver, Dallas, Minneapolis, Orlando and Seattle, using their specific code requirements.

It found that by providing daylight from above via skylights, the total fenestration area could be reduced from a maximum 20 percent of floor area to as low as 12 percent of floor area while achieving the same baseline average of daylight factor target of five percent.

This was found to reduce annual heating and cooling energy use and costs in all but two of the 108 models with skylights that the group analyzed. Lighting savings, shading efficiencies, and increased natural ventilation attributable to skylights were not evaluated for simplicity. Further studies are planned to look into quantifying these additional efficiency contributions.
“While we have always known the intangible benefits of adding daylighting from above to homes, this study provides empirical evidence that natural light from skylights can contribute to the home’s overall energy efficiency,” said Stephan Moyon, direct of sales for VELUX America.

An in-depth discussion of the study, as part of a GreenExpo365 webinar titled “How To Reduce Energy Use By Improving Daylighting,” is available online. The full study report is available from VELUX upon request. VELUX continues to study and document the role and effectiveness of skylights in providing daylighting and passive ventilation.

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