Daylight shapes the experience of a space like no other material and is a fundamental aspect for designing healthy and sustainable buildings. Good daylighting design can improve the health, mood, cognitive abilities and productivity of the occupants at home, school or work while reducing the energy consumption of buildings.
Daylight Visualizer makes it easy to take informed decisions about architectural and daylighting strategies in your projects, and to evaluate compliance with requirements for daylight performance in building regulations and building rating systems.
How to measure and evaluate daylight in buildings?
Illuminance and luminance
Daylight can be measured in terms of illuminance and luminance, two words that sound similar but should not be confused. Illuminance is the measure of the amount of light received on the surface and is typically expressed in lux (lm/m2). Luminance is the measure of the amount of light reflected or emitted from a surface and is typically expressed in cd/m². The figures below show illuminance and luminance renderings, with and without false colour applied, for an atrium space in a school project.
Illuminance simulations are used to evaluate the quantity of daylight that will be available in interiors, as well as its distribution and uniformity in the space, and it is typically calculated at a work plane height. Luminance simulations are used to evaluate the risk of glare and visual discomfort, and it is typically calculated for a range of occupant positions and view directions in the room.
Daylight factor
Daylight factor (DF) is an illuminance-based daylight availability metric that expresses as a percentage the amount of daylight available inside a room (on a work plane) compared to the amount of unobstructed daylight available outside under overcast sky conditions, as illustrated in the figure below.
The output from a daylight factor simulation is presented in a plan view with false colour or iso-contour lines applied for showing corresponding daylight factor levels in the space. It is common practice to evaluate the daylight performance of a space based on the achieved median daylight factor, which is a valid method to evaluate requirements found in the European Standard for Daylight in Buildings EN 17037 and other building rating systems. The figure below shows a daylight factor simulation performed for an atrium space in a school project where a median daylight factor of 10.87% is achieved.
Why are daylighting simulation tools important?
There are several factors impacting daylight availability and quality in buildings which make simple rules of thumb like glazing-to-floor area ratio inadequate to prescribe good daylighting. The climate, latitude, building site context and building design all have a large influence on the amount and distribution of daylight in interior spaces. Daylighting simulation tools like Daylight Visualizer are capable to address this complexity and accurately predict the daylight performance of a building prior to its realization. The figure below shows how the daylight performance of a room with 10% glazing-to-floor area changes based on the window distribution, where the third situation achieves a median daylight factor 3x higher than the first.
Intuitive workflow and compatibility
The intuitive user interface of Daylight Visualizer makes it easy to create simple 3D models from scratch within minutes with the embedded modeler and lets you import existing projects from your preferred BIM/CAD software in any level of details. Find various tutorials showing how to use the Daylight Visualizer on our YouTube channel VELUX BIM & Building Simulation Tools.
