What is the most sustainable light source for public spaces?

Daylight is the most sustainable light source because it is a natural, renewable resource that consumes zero operational energy. The primary goal of sustainable lighting design is to maximize the use of daylight to reduce or eliminate the need for electric lighting during daytime hours. This approach significantly lowers a building's energy consumption, operational costs, and carbon footprint. While LED technology is the most sustainable electric option, it still requires energy and has environmental impacts from manufacturing and disposal. Daylight, as a source, has none of these operational or end-of-life drawbacks, making it the superior choice from a holistic sustainability perspective.

A. LED: While the most energy-efficient and long-lasting electric light source, it still consumes energy and has an environmental footprint from its manufacturing and disposal lifecycle.

C. Halogen: This is an inefficient incandescent technology with a very short lifespan and high heat output, making it one of the least sustainable choices.

D. Fluorescent: Although more efficient than halogen, fluorescent lamps are less efficient than LEDs, have a shorter lifespan, and contain toxic mercury, which poses a disposal hazard.

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1. The IES Lighting Handbook

10th Edition. Illuminating Engineering Society

2011.

Section 26.4

"Sustainable Lighting

" states

"The first consideration for sustainable lighting design is to use daylight as the primary source of daytime illumination whenever and wherever it is available and practical." This establishes daylight as the top priority in sustainable practice.

Chapter 8

"Daylighting

" details the methods and benefits of using natural light

emphasizing its role in energy conservation.

2. Grondzik

W. T.

& Kwok

A. G. (2019). Mechanical and Electrical Equipment for Buildings (13th ed.). Wiley.

Chapter 17

"Lighting

" discusses the principles of sustainable lighting design

consistently prioritizing daylighting strategies (sidelighting

toplighting) before considering electric sources. It notes that "the most energy-efficient light source is daylight."

3. U.S. Green Building Council. (2019). LEED v4.1 Building Design and Construction.

Credit: EQc Daylight

The existence and high point value of this credit within the world's leading green building rating system formally recognizes daylighting as a critical and highly valued component of sustainable design

intended to "reduce the use of electrical lighting by introducing daylight into the space."