Essentials of designing with LED

LED lighting design has many advantages over previous lighting sources, enabling designers to deliver more to their clients.

08/21/2018


Learning Objectives

  • Identify key characteristics and functional lighting advantages of LED technology.
  • Understand how to apply LEDs to support project-specific lighting goals and criteria.
  • Understand considerations and coordination items required to design a project using LED systems.

LED technology offers several key advantages over legacy lighting sources, enabling lighting designers to deliver more to their clients. With proper identification of LED opportunities at the onset of a project and thoughtful coordination of the systems and equipment needed to achieve the team's design goals, these advantages are leveraged to create lighting solutions that are more sustainable, flexible, and maintainable than before.

Before diving into product selection and lighting layouts, designers should always begin by assessing the needs of their clients. Each project is unique in size, shape, and geographical location, let alone programmatic and stylistic requirements, which call for a fresh set of lighting solutions at the onset of each endeavor. A client's opinions on the way they'd like their spaces to look, feel, and function and their energy efficiency goals will have a direct effect on the designer's approach in establishing the project's sustainability guidelines, as well as determining color temperature, color-rendering requirements, and other design criteria.

One of the biggest advantages of LED technology is the ability to save energy. LED technology is continuously advancing, and with that comes improved energy efficiency. Today's LED boards and drivers are able to produce more light at lower wattages than the majority of older lighting technology-many manufacturers now have the ability to provide products with 100+ lumens/W. As lighting-power density (LPD) requirements for building codes become more stringent and sustainability certifications become more prevalent, the efficacious lumens per watt provided by LEDs become necessary elements to include in the design of energy-efficient lighting systems.

Figure 1: This cafeteria uses linear lensed LED slots, curving LED tapelight, backlit stretched ceiling with LED arrays, recessed LED downlights, and suspended LED cylinders. All graphics courtesy: Cannon Daylight harvesting

Access to daylight can contribute significant energy savings within a building. Whether required by code or installed for best practice, photosensors monitor light levels in a space and adjust fixture outputs to maintain a footcandle level acceptable to the space. As the LEDs are dimmed, the current supplied to the fixtures decreases, lowering the wattage required to power the fixture.

The energy usage is fairly linear when dimming LEDs, meaning when reduced to 50% they are using roughly 50% of their full energy consumption, depending on the quality of the driver. Along with the energy savings, daylight controls also provide the benefit of longer fixture life. As LEDs dim in response to higher daylight levels, the lower drive current to the LED boards produces less heat, which prolongs life. The more daylight dimming control in a building, the longer the fixtures will last.

The low power consumption of LEDs enables greater efficacies, and their ability to be easily controlled allows them to be leveraged for daylight harvesting and other energy-saving control strategies. The resulting energy savings can be significant-often upward of 35% to 40% when compared with legacy systems like fluorescent, incandescent, and high-intensity discharge (HID)-making lighting a major contributor to project sustainability.

Sustainability requirements are determined by a number of factors, but the most basic design drivers are the codes and standards established by local governing bodies. The assigned code can greatly affect the lighting design and fixture criteria, making early consideration critical. These standards must be met in order to obtain approval to construct.

Codes, standards, and guidelines

Relevant codes for lighting design include but are not limited to the International Building Code (IBC), International Energy Conservation Code (IECC), and ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings. While there are variations within each code, these codes establish LPD metrics, emergency and egress light levels, and minimum lighting control strategies as the major requirements. Each code has multiple editions and is updated regularly (typically a 3-year cycle), as technology changes drive improved efficiency and safety requirements.


The version of code is assigned to a project based on the start year and the building standards that the local governing body follows. Some areas of the country follow stricter codes-such as California's Title 24-making it important to stay up to date with lighting requirements in various regions.

Another strategy for addressing sustainability is choosing to design to the U.S. Green Building Council's LEED guidelines. The LEED system establishes a checklist of design guidelines to follow, but unlike building codes, designers don't have to satisfy all items. The more sustainable strategies incorporated into the building design, the more points earned, and the higher the level of certification received: LEED Platinum, Gold, Silver, or Certified can be achieved through sustainably focused design.

There are slightly different checklists for different project typologies, but each contains several credits related to lighting, which include control strategies, building LPD, lighting-fixture quality, daylighting, and other best practices. These credits are significantly more achievable with LED technology. Like codes, LEED is updated as technology improves, and the current version is LEED v4. Other certification programs, like the WELL Building Standard, are emerging with a slightly broader range in addition to a focus on energy efficiency and the role lighting can play.


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