Design and assessment of daylit spaces—the best way to use daylighting metrics

The end goal of daylighting is often better defined than the path to success. Correctly applying daylighting design in major retrofits and new buildings can be challenging.

08/15/2016


Learning objectives:

  • Describe the complexities of daylighting design and analysis.
  • Understand the type of simulation used for various daylighting metrics.
  • Recall considerations of fabric selection for a daylighting design.

Craig Casey is a senior building science engineer at Lutron Electronics Co. Inc. He works in the Energy Information and Analytics group conducting applied research on energy and the human benefits of lighting and daylighting controls. Courtesy: Lutron EleDaylighting, almost an afterthought less than a decade ago, is quickly becoming a cornerstone of high-performance building design. The U.S. Department of Energy acknowledges both the energy-saving and human-centric benefits of daylighting in its Lighting Development, Adoption and Compliance Guide, and federal requirements increasingly include daylight control in building codes and standards. Lighting and light control is connected to just about everything in a building—building energy systems, building codes, occupant health, and productivity.

Learning objectives:

  • Describe the complexities of daylighting design and analysis.
  • Understand the type of simulation used for various daylight metrics.
  • Recall considerations of fabric selection for a daylighting design.

As with many emerging trends and technologies, the end goal of daylighting is often better defined than the path to success. Correctly applying daylighting design in major retrofits and new buildings can be very challenging.

Tools for accurately simulating daylight metrics, creating appropriate system layouts, and calculating energy savings are limited, but progressive manufacturers are working on new simulation techniques that empower lighting consultants and specifiers to get involved early, understand available data, and provide their clients with the ideal total lighting environment.

What's so tricky about daylighting design?

It's simple. Daylight is dynamic; constantly changing throughout the building environment. The sun moves within the space. It's very bright. Sky conditions change. And every change to the exterior environment has a direct, measurable effect on the daylight space it impacts.

Good design requires multiple decisions based on the dynamic nature of daylight. The size, number, and location of apertures is a key piece of information, along with the specific space layout, and knowledge of the glazing materials and shading devices (such as manual or automated shades, light shelves, louvers) planned for use throughout the space or building.

New tools, such as the Performance Shading Advisor from Lutron, allow specifiers to simulate daylight conditions for their projects, helping to ensure appropriate shade-fabric selection. Courtesy: Lutron Electronics

Heating and cooling loads are significantly affected by lighting control, and energy saving goals typically demand effective total-light-management strategies. Developing products that fit this increasingly complex mix of needs—healthy daylighting, not too much glare, and artificial lighting controlled to maximum efficiency and productivity—depends on well-implemented integration and professional collaboration.

Simulation methods and essential metrics

Space simulations help you specify the ideal lighting control environment, the right shading fabrics, and the right control methods. The earlier these simulations are performed, the more accurate your data is—and the more value you can bring to your client. Work with a manufacturer who can help you identify the right data points and the best methods for collecting and analyzing cogent project information. Once you collect the right data, you'll be better able to analyze lighting system needs and calculate key metrics.

Effective daylighting strategies rely upon accurate information about shade-fabric performance with regard to glare reduction, daylight autonomy, and view preservation. Courtesy: Lutron ElectronicsPoint-in-time simulations help provide data for specific times of day in specific building locations. Analyzed as a unit, these simulations paint an accurate picture of how lighting affects the total space over time. Simulation options may include:

  • Renderings for assessing daylight distributions and sunlight patterns at particular times of day
  • Illuminance calculations and/or contours at analysis points across the space/building 
  • Applying standard sky conditions, such as clear vs. overcast skies.

Annual simulations will, in turn, help develop metrics, such as:

  • Hourly illuminance values at each calculation point
  • Annual metrics that include continuous daylight autonomy and useful daylight illuminance
  • New data points that can help contribute to LEED certification; spatial daylight autonomy and annual sunlight exposure metrics

Metrics empower you to make the best recommendations for every client. Another critical factor in effective daylighting management is shade-fabric selection. Once you understand the subtleties of the space environment, there are simple tools to help you find the perfect balance of aesthetics and performance in the shade material itself. The optimal fabric is essential to reducing glare, maximizing daylight, and preserving views, all of which have a profound impact on the occupants in the space.

Effective daylighting strategies rely upon accurate information about shade-fabric performance with regard to glare reduction, daylight autonomy, and view preservation. Courtesy: Lutron ElectronicsProgressive manufacturers are developing tools to make these simulations easier and to help you use the information to design an integrated lighting and shading control solution that meets the unique needs of your space. Integrated lighting and shading controls automatically, and unobtrusively, respond to defined environmental conditions to maximize comfort, reduce energy use, and meet the constantly changing needs of the building environment.

Work with companies committed to empowering you with updated tools and product solutions so you can make informed lighting control recommendations to your clients, meet and exceed building codes and standards, and ensure clients have solutions that will meet the needs of their building today and for the life of the space.

-Craig Casey is a senior building science engineer at Lutron Electronics Co. Inc. He works in the Energy Information and Analytics group conducting applied research on energy and the human benefits of lighting and daylighting controls.



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