Daylighting is a common component of any newly designed commercial or residential space. By controlling the admission of natural light into a building, the architectural design can affect not only how well the inhabitants see, but feel. Natural lighting has been shown to increase worker happiness, decrease absenteeism, and increase productivity. Thoughtfully including daylighting techniques into the whole building design will create a visually comfortable environment and reduce as much as one-third of total energy costs.
Daylight Design Standardization
In 2000, the U.S. Green Building Council introduced the Leadership in Energy and Environmental Design (LEED) rating system to standardize metrics for many sustainable design characteristics, including daylight. Realistic comparisons of daylight design and performance were further developed in 2013, when the Illuminating Engineering Society adopted and published the test and calculation guide Lighting Measurement 83 (LM-83).
LM-83 is an evidence-based daylighting performance metric that has helped to standardize the practice and provide expectations that can be referenced in project specifications and requirements. For example, as part of the metric, floor areas in a building that achieve 300 lux (the SI unit of illuminance equal to one lumen per square meter) for at least half of the analysis hours counts as meeting the daylighting threshold.
A Spatial Daylight Autonomy (sDA) associates a value with how much of the space receives adequate natural light and can range from 0-100 percent. Generally speaking, an sDA value of 75% indicates a space where daylighting is enough for employees to work comfortably without the use of electric lights. As such, lighting designers should aim for an sDA value of 75% or higher in commonly occupied spaces like classrooms, offices, and storefronts.
Daylighting Design Best Practices
Space Planning and Windows
When designing a building, place rooms that will be highly occupied during the day along the south-facing walls. Rooms facing this direction will receive the majority of the day’s sunlight. Window’s not only open the space up to beautiful vistas, but if thoughtfully placed, can increase worker productivity and save on energy use.
Windows placed on the south facing wall of any building in the United States are best for maximum natural light, especially during the shorter winter months. They also receive little direct sunlight during the summer, avoiding an interior cooling issue when things really start to heat up outside. North facing windows will also let in natural light with reduced glare and summer heat, but windows facing east or west won’t bring in that coveted daylight. There is light, but also excess heat and glare. Keep in mind, windows designed high on the wall will bring in the most natural light, but also the most heat.
To account for glare and reduce heat in the summer, place hoods on the exterior of the windows or get tech savvy by installing “smart glass” windows that change from light to dark with the push of a button.
Combine window placement with skylight installations to optimize daylight within any space. There are a variety of skylights on the market, so be sure to access your building’s needs, geographic climate, and the energy star performance ratings of skylights before planning.
The size of the skylight will affect the illumination level and temperature of the space. The size should never be more than 5% of the floor area in rooms with many windows and no more than 15% of the room’s total floor area for spaces with few windows. Skylight on roofs that face north provide constant, cool illumination, those on east-facing roofs will provide maximum light in the morning, while west-facing skylights provide afternoon sunlight. South-facing skylights will bring increased solar heat in the winter months, but potentially unwanted heat in the summer. Skylight glazes and movable window coverings on the outside or inside of the space can help control heat gain and loss.
Lighting Control Systems
Spaces generally can’t function on daylight alone and some level of electric lighting is required, but installing a lighting control system along with LED lightbulbs can help control utility use.
With lighting control, it’s possible to adjust the level of electric light depending on time of day and sunshine intensity. Switching, stepped, and dimming controls paired with sensors and timing devices allow users to remotely adjust the level of light in use at any time.
It’s best to design a space with a lighter colored ceiling to reflect and enhance daylight. Mirrors are also a great tool in shadowed areas as they will bounce and redirect any natural light available. Using bright colors and finishes on the walls will also help reflect sunlight.
LEDs: The Best Alternative
Architects and designers who are considerate of daylighting techniques also look for the next best alternative when it comes to sustainable electric lighting. EarthTronics eco-friendly LED EarthBulbs emit a bright, pure white light that is comparable to natural light, and greatly reduces energy usage when compared to their fluorescent lighting counterparts and EarthTronics offers an advanced T8 LED product line that works with daylight harvesting dimming controls.
Daylighting requires an integrated design approach that involves decisions related to building form, climate, space planning, building components (such as skylights and windows), and lighting design. To learn more about whole building design click here. When daylighting isn’t possible, LEDs serve as the best alternative to natural daylight – and EarthTronics carries an extensive inventory of environmentally friendly, cost effective EarthBulbs, made to fit the needs of your next construction project or retrofit.