How to Consider Lighting Design for Healthier Buildings
Daylight design is an important aspect of creating brighter, healthier buildings for everyone. Given the unique ability of daylight to shape the experience of space, architects and designers must take this into account in order to create healthier, more sustainable buildings. Good daylighting design can improve the health, mood, cognitive performance and productivity of occupants in a home, school or workplace, while reducing a building’s energy consumption.
We explore some of the key factors that can affect a building’s daylight availability and how to factor them into your next project.
climate and latitude
The prevailing climatic conditions of the building site determine the overall prerequisites for its daylighting design, including daylight availability, visual comfort, thermal comfort and energy performance.
Location latitude determines the altitude of the sun at any given time of day and year. Summer and winter sun height characteristics are important design inputs for the availability and control of direct sunlight. For example, the graph below shows the difference in outdoor illuminance (lux) levels and day lengths between northern and southern Europe.
External obstructions to elements (buildings, vegetation, ground, etc.) surrounding a building site can have a huge impact on the amount of sunlight reaching the interior, the availability of direct sunlight, and the quality of window views. This is a key factor to consider when analyzing the solar performance of a building design. The figure below shows the striking differences in barrier levels between rural and urban environments, underscoring the need for rigorous daylight planning when designing in dense urban environments.
The geometry of a building affects its ability to provide sufficient daylight to interior spaces. When the building is deep, lighting only through the façade windows has its limitations. Regardless of how much glass the façade has, sufficient daylight distribution is only achieved a few meters from the façade (in spaces with typical ceiling heights). The graph below shows the Daylight Factor (DF) levels obtained in a deep room with 3 different window configurations.
The color and reflectivity of the room surfaces are part of the daylighting strategy. Dark surfaces reflect less light than bright surfaces, and the result is likely to be an unsatisfactory glowing environment with little indirect or reflected light. Bright vertical surfaces in rooms are generally preferred over dark surfaces, but shading devices used to control sunlight should use darker materials to limit the risk of glare when prominently visible to building occupants. The graph below shows the effect of surface color and reflectivity on brightness levels.
Window orientation, size and position
The orientation of windows can affect the availability and quality of indoor daylight, especially in the presence of direct sunlight. Roof windows installed on flat or low roof slopes are less sensitive to orientation if they have unobstructed views of the sky.
The amount of sunlight entering a room is directly related to the total glass area of the windows in the room and the visible transmittance value of the glass. As a rule of thumb, double glazing (uncoated) approx. 80% of the light, while triple glass (uncoated) lets in about 80% of the light. 70% light.
The position of the windows affects the distribution of daylight in the room and determines the amount of “useful” daylight. Window placement should also take into account the relationship between the outside view and the occupant’s eye level.
VELUX Daylight Visualizer is a free, easy-to-use and powerful daylighting simulation tool that can be used to evaluate the impact of all these factors on the daylighting performance of a building project. The image below shows how the addition of roof lights improved daylight conditions in a school project in Germany.
Download your free copy of Daylight Visualizer today and start your journey to become a leader in daylighting design.