Architects such as Alvar Aalto and Tadao Ando showcase the ability of natural light to shape architectural spaces. Aalto's projects employ extensive glass elements, carefully positioned windows and skylights, harnessing the ever-changing characteristics of daylight. Meanwhile, Ando's Church of Light serves as a striking example of how light can hold profound spiritual significance within a space. Its concrete facade features a symbolic cross-shaped opening, which beautifully and symbolically illuminates the interior, creating a unique spiritual ambiance. In addition to being an essential element that enhances interior aesthetics, natural light profoundly impacts the overall quality of life, promoting better well-being and productivity. By taking advantage of the power of natural light, spaces can reduce their dependence on artificial lighting, leading to greater energy efficiency and a more sustainable design approach.
This is why daylight modeling is crucial for designing and implementing effective strategies to incorporate this (free!) resource into buildings. Done through advanced 3D simulation software, it makes it possible for architects, designers, and engineers to evaluate and compare different design options, check light levels between spaces, or even predict sources of excessive glare that may be unpleasant to occupants. It can be incorporated from even the earliest stages of design, assisting with the most appropriate solar orientation and in the massing study. It can also compare design options, select the most suitable materials for each part of the project, and assist in the sizing and location of openings such as windows, skylights, and sunscreens.
Kalwall is a company specializing in the production of energy-efficient daylighting systems. Its flagship product is the lightweight Kalwall panel, a high-performance structural translucent composite used in a wall or roof system known for its unique ability to diffuse natural light while maintaining superior thermal insulation properties and providing visual privacy. In addition, it offers products related to translucent building systems including windows, skylights, and curtain walls, designed to optimize the use of natural light in architectural design. To really help designers take maximum advantage of natural lighting in their projects, it also offers daylight modeling support.
Several metrics are used to assess the performance of a building to be built or renovated. By understanding these metrics and applying them to projects, architects and designers can optimize the project's objectives according to its use, while also adapting to local regulations or even sustainability certifications, such as Leed®, CHPS, BREEAM®, and Well ™ V2, which make use of metrics to confer scores. The main lighting metrics are the following:
Radiance and Illuminance are the two initial concepts to be considered. Radiance refers to the total energy that is reflected, transmitted, or received by a surface, per angle per area. It is a metric that evaluates specific light levels on a predetermined day and time, simulating localized sky conditions. Illuminance, on the other hand, measures the amount of light emitted by a source and received by a surface. It is quantified in lux (lumens per square meter) or footcandles (lumens per square foot).
Useful Daylight Illuminance (UDI) is a lighting metric that measures different lux levels (luminous flux per unit area) in a space. Specifically, it calculates the percentage of the floor area in that space where the illuminance level falls within a certain range, considering this over 50% of the time. Lux levels below 100 are generally insufficient for most tasks, while 100-300 lux is sufficient but may require additional artificial lighting. The desirable lighting level falls within the range of 300-3000 lux. Exceeding this can lead to visual and thermal discomfort.
Spatial Daylight Autonomy (SDA) measures the amount of daylight throughout the year that exceeds a specified illuminance level (e.g. 300 lux) in a given area, typically 10 hours per day, 365 days per year.
Annual Sunlight Exposure (ASE) assists in limiting excessive exposure to sunlight in a space, which can cause excessive glare and solar heat gains. As such, it represents the percentage of a space where direct sunlight exposure exceeds a predefined threshold (e.g. 1000 lux) for a given number of hours during a year.
Another similar metric is the Visual Daylight Glare Probability (DGP), which helps identify problem areas where glare is a concern, particularly in work and study areas. Different levels of DGPs indicate varying degrees of glare, ranging from noticeable to disruptive and intolerable.
On the other hand, Equivalent Melanopic Lux (EML) is used to measure the biological effects of light on humans, considering the impact of lighting on circadian rhythms.
To exemplify the analysis, Kalwall provides an example of a common area at a high school in the Pacific Northwest. In this project, Kalwall's unit skylights are used, as well as a vision glass wall. The power of daylight modeling allows the design team to see where direct sunlight through glass could be an issue that needs to be addressed. This can be done through materials in separate glass panes or by changing the openings created.
By utilizing daylight modeling to analyze and optimize design strategies, architects and designers can provide evidence of meeting specific requirements and sustainability goals, facilitating the certification process for sustainable building designs. This helps maximize the benefits of natural light, including reduced energy consumption, improved occupant well-being, and enhanced architectural aesthetics. By leveraging technology and scientific analysis, daylight modeling creates well-designed, sustainable, and human-centric spaces.
