Ample daylighting and window views can help make your next building net-zero, healthier, and more sustainable.
By Lisa Heschong, Fellow Illuminating Engineering Society
“Daylighting” is the process of designing and operating interior spaces to utilize natural daylight as their primary source of illumination. Optimizing the distribution of daylight illumination requires climatically appropriate architectural design, cognizant of locale, climate and orientation. Daylight optimized interior design and furniture layouts enable occupants to take maximum advantage of the available daylight; electric lighting design responds to the dynamics of daylight, providing supplementary illumination only where and when necessary. Occupants in successfully daylit buildings regain control of their environment, with the ability to make local adjustments to furniture, window shading systems, and electric lighting to best meet their changing needs over the course of the day and year.
There are many fenestration design strategies, including windows, skylights, atria, and sunlight redirection devices, that can contribute to successful daylighting. Multiple approaches often make for a more robust system. Ultimately, daylighting both benefits from and encourages a holistic design approach; one which integrates input across design professions and establishes performance goals that are pursued continuously throughout building design and operation. Thus, daylighting is a fundamental benefit of good architectural design and coordination.
How are window views different from daylighting?
Windows designed for views provide occupants with a visual connection to the outdoor environment. While view windows may also deliver daylight illumination into a space, they do not necessarily need to be optimized for that purpose. Via thoughtful design, architects become curators of good views, which can add enormous financial value to buildings.
Occupants may get more circadian health benefits[i] from window views than from interior ambient illumination. This is because window views are generally brighter and more interesting, thereby attracting occupants’ attention, both consciously and unconsciously. Window views have also been associated with many other health benefits, including eye health, cognitive performance, and emotional well-being.
How are daylighting and window views related to climate change?
Efficiency: Using daylight as the primary illumination sources inside of buildings during the daytime is inherently energy efficient. No electricity is needed for most of the daylight hours. Fully daylit buildings can be extremely efficient, by using passive solar design principles. During cold weather, sunlight can be utilized for both light and heat (as long as it is ‘gentled’ first, to avoid overheating or glare.) During warm weather, daylight from the sky and broadly diffused sunlight can be more efficient than equivalent electric light sources, contributing less net heat per unit of light and so further reducing building cooling loads. Views can also add to building energy efficiency, by providing the bright vistas that occupants crave, without a need to increase electric lighting power densities.
Sustainability: Daylighting may be the ultimate sustainable design practice. Well daylit buildings have endured for hundreds of years. Buildings with ample daylight and views are easily repurposed, from offices and factories to schools and homes. Windows and glazing materials are long lasting. They can easily last for 50 (or more) years, compared to a 15-to-20 -year life for many electric lighting systems and the current 5-10 year change-over cycle for new electric lighting technologies . While glass industries do utilize a lot of energy, the materials are simple, widely available, and non-toxic. Likewise, maintenance is a piece of cake: water with a little soap or vinegar
Resilience : Daylight is the most reliable and resilient form of interior illumination. It works regardless of power availability and grid reliability. You want to be in a daylight building when your power supply is uncertain, such as after an earthquake, a flood, or a fire storm.
Simplicity : Daylight from windows is easily managed using common materials and common sense, such as curtains, blinds, awnings. Repairs and re-configuration do not require an electrical engineer or computer programmer (as with advanced electric lighting controls.) Thus, in case of failure or reconfiguration, any problems can be easily and quickly solved.
Emergency response: Window views provide essential information about our environmental context, enabling occupants to assess sudden weather changes and other threats. They can also enable essential emergency communication and egress options.
Health: This is the big one. What’s the point of climate adaptation if it leaves people sick or uncomfortable? We now know that we need the circadian cues from daylight (and dark nights) to stay healthy. We have specialized photoreceptors which seek signals from the dynamic colors of daylight to keep our fundamental body and cellular rhythms in sync. Views are likely the most potent form of circadian stimulus inside of buildings, because they are bright; perfectly in sync with the exterior illumination; and most of all, interesting, drawing our attention. As a result, ample daylighting and views are an essential component of IEQ—indoor environmental quality.
Happiness: Daylight and views make people happy. They have been shown to lower depression and anxiety. They have also been shown to motivate healthy behaviors, like more physical activity and better sleep patterns. We could all use a little more happy.
Things you can do right now:
Design buildings that use daylight as the primary form of interior illumination.
- Create spaces that have daylight entering from more than one orientation, such as view windows on two or three sides, entering from high windows like clerestories, and/or entering from above, such as from skylights, roof monitors or atria.
- Design the electric lighting to supplement the daylight only when and where needed, and to provide appropriate nighttime illumination.
Use clear, highly efficient glazing materials that provide maximum light transmission per window area (VLT of 60% or greater).
- Both people and plants benefit from the full spectrum of sunlight, so avoid glazing tints or coatings that change the appearance of the glass.
- Instead, minimize heating and cooling impacts via proper shading, orientation, use of triple or quadruple glazing layers, and by keeping total glazing area to the minimum needed for well-balanced daylight and views.
- Operable shading systems can also be designed to improve both heating and cooling profiles, thus reducing whole building energy use. When closed during nighttime operations, such operable shading systems also improve privacy and reduce light pollution.
Avoid allowing too much direct sunlight into the space that may cause visual or thermal discomfort for the occupants.
- Pay careful attention to solar geometry, and wherever possible, provide exterior shading for windows during the hottest times of the year.
- View windows should also include occupant-controlled blinds or shades to provide intermittent privacy and glare control.
- Skylights should be diffusing to ‘gentle’ the sunlight and spread daylight broadly
- Clerestories and roof monitors should be carefully sized and oriented so that any direct sunlight entering the space will reflect off of another surface at least once before it reaches any eyeballs.
Use design analysis tools that will help you understand the dynamics of daylight in the space. This can include physical models combined with photography and physical measurements, or computerized simulation models that are capable of hourly daylighting analysis.
- If you don’t have the expertise to do daylighting analysis in-house, hire a daylighting consultant.
- Go visit well-daylit buildings and analyze the strategies used. Learn from the masters.
- Read up on daylighting design and analysis in the resources listed below.
Advocate for daylighting design to your clients, to other building owners and occupants, and to public officials.
- Access to daylight and window views during the day should be a basic right for all workers. It is a fundamental equity issue for healthy indoor environments.
- Help your mechanical and electrical subcontractors better understand how to design in response to the dynamics of daylight, rather than ignoring it or fighting it.
- Advocate for minimum daylighting and view requirements in building codes, especially for vulnerable populations such as children, the elderly and low-wage workers.
Seven very different books that cover a wide range of the art and science of daylighting:
- Visual Delight in Architecture: Daylight, Vision and View by Lisa Heschong, Routledge 2021.
An exploration of the many ways that daylighting and view are important for our health, well-being, social structures and culture, derived from both recent research and personal experience.
- The Architecture of Natural Light by Henry Plummer, The Monacelli Press 2009
A lush photographic tour of beautiful daylit spaces designed by great architects
- Approved Method: IES Spatial Daylight Autonomy(sDA) and Annual Sunlight Exposure (ASE), published by the Illuminating Engineering Society, 2013
A manual explaining a methodology used to analyze daylight illuminance adequacy in commercial spaces. Soon to be updated. preview_IES+LM-83-12.pdf (ansi.org)
- Effective Daylight for High Performance Facades by Kyle Konis and Stephen Selkowitz. Springer 2017
The latest synthesis of work by Lawrence Berkeley National Labs on advanced daylighting strategies and technologies, packed with technical data and examples.
- Daylighting: Architecture and Lighting Design by Peter Tregenza and Michael Wilson, Routledge, 2011
A seasoned educator’s guide to architectural daylighting design, including tools, graphics, and case studies.
- Windows on the World by Matteo Pericoli, Penguin, 2014
A delightful collection of hand drawings of window views from around the world, accompanied by loving descriptions by the writers who live and work with those views.
- Sunlighting as a Form Giver for Architecture by William Lam, Van Nostrand Rienhold, 1986
Old school daylighting advice and case studies by one of the early masters, using physical models for analysis. Out of print, but available used:
More extensive daylighting bibliographies with short reviews:
BOOKS – The Daylight Site | Daylighting research, architecture, practice and education The Daylight Site
77 Best Lighting Design Books | ArchDaily
Daylighting Pattern Guide – New Buildings Institute
A free, interactive tool that helps design teams incorporate proven daylighting strategies into commercial building projects for reductions in lighting power consumption and overall building energy use, from 2015.
“Visual Delight – The Importance of Views in the Workplace” by Lisa Heschong – YouTube
A preview of some topics covered in Visual Delight in Architecture, from a17 minute talk by Lisa Heschong in 2019.
[i]The term ‘circadian’ refers to our body’s daily rhythms, synchronized to the 24-hour day-night cycles of the planet. Biologists have found that every cell in our body follows these rhythms, and just like a complex orchestra, they need a steady signal from a conductor to keep them all in sync. That signal is provided via light receptors in the retina. Disruption of circadian rhythms is associated with impaired sleep, cognitive performance, immune response, and metabolic function; it is also associated with weight gain and obesity, diabetes, hypertension, heart disease, stroke and depression. (For further detail see Chapters 1-3 of Visual Delight in Architecture (Routledge 2021) in references)