Shedding Light on Daylighting: A Comparison of LEED, WELL, Fitwel, and LBC Credits
By Shruti Narkar
Shruti is a Project Management & LEED Intern at Verdical Group. She is currently a student at Savannah College of Art and Design (SCAD) pursuing her Master of Arts in Design for Sustainability. She is a LEED AP BD+C and Fitwel Ambassador.
The positive effects of daylight on human health & wellbeing have been studied for many years, and the results of these studies have been well-integrated into green-building & wellness-centered rating systems.
This article will analyze daylight credits across four rating systems: LEED, WELL, Fitwel, and the Living Building Challenge, to understand their unique intent and documentation requirements. Understanding the nuances, synergies, and interconnections within these rating systems can help us in designing better strategies for successful green buildings. It will also enable us to see the possibilities and likely outcomes of combining different rating systems to improve occupant health and maximize building performance.
We created a table listing the four rating systems and discovered the following similarities & differences:
All four rating systems highlight the importance of daylight and its impact on occupant health. In addition, LEED goes a step further by also considering the benefits of daylighting in reducing the total electricity usage of the building, while WELL specifically emphasizes the importance of lighting to reinforce circadian rhythms.
LEED and WELL requirements for daylight focus on using simulated daylight analysis and actual measurements to estimate daylight quality and daylight levels, while Fitwel requirements focus on calculating the planned percentage of daylit area within the project by taking window design into account.
While LEED uses daylight as a natural resource to conserve energy, WELL uses it to stimulate circadian rhythm in the human body.
Both LEED and WELL have an option to demonstrate compliance using either daylight modeling to simulate Spatial Daylight Autonomy (sDA) or through illuminance calculations. The criteria for the LEED daylight credit align with WELL and Fitwel, with a range of options available for alternative compliance.
While circadian rhythm is such a large part of WELL, there is no equivalent in LEED that corresponds to WELL L03: Circadian Lighting Design. On the other hand, while LEED pushes for less energy use, WELL often requires more energy use to produce lighting that promotes emotional and physical wellness.
In terms of documentation, LEED methods of using simulated daylight analysis and actual measurement help in accurately predicting daylight access and support the design process for optimizing daylight. The Fitwel method for calculating daylight using window design less accurately accounts for project-specific factors such as building orientation, exterior conditions, the interaction with interior finishes, time of day and year, and other performance variables.
While each of these rating systems have their own unique lens of looking at daylight credits, it is important to note that they were all designed with a common intent to promote occupant health, and in some cases also improve building performance. Creating a balance with a combination of these rating systems, or bridging the gap between these rating systems, will in turn allow the project to be both environmentally responsible and cognizant of human health benefits.
Download the complete chart here.