by Monika Maragkou and Nicolas Roy, VELUX Group

Sunlighthouse is a VELUX Model Home 2020 residential building in Austria. The main objective of the Model Home 2020 initiative is to create environmentally-friendly low-energy buildings with a strong focus on the health and well-being of their occupants. A key factor for achieving this is to provide the interiors with generous levels of natural light. Daylight performance analyses were actively used during the design process of Sunlighthouse and following are the final results from the evaluation in Daylight Visualizer.

Daylight Factor

The images below show the simulated daylight factor for the ground (left) and first floor (right). Daylight factor calculations are a recognized method for evaluating the light levels (at workplane height) in the different rooms of the house. Simulations like these can assist design decisions, for example when deciding how many windows should be used and where they should optimally be placed, depending on the design goals of the project.

F0 (smaller) F1 (smaller)

Results by individual zones

It is possible to model individual zones in imported geometry in order to obtain additional results such as the maximum, minimum, average and median Daylight Factor and uniformity indicators and to generate an html report including all these values.

Click here to view the html report.


Besides the Daylight Factor, the daylight performance of Sunlighthouse was also evaluated by simulating the illuminance levels in different parts of the house during various times of the year and sky conditions. The following two images show the illuminance levels in the dining room under a CIE intermediate sky on June 21st (top) and December 21st (bottom) at 12:00.

Connected_Illuminance_June_1200 (smaller)

Connected_Illuminance_Dec_1200 (smaller)

The values displayed in a grid on each image are in lux. The glazing appears black because it is recognized as a light source and therefore not a light-receiving surface. With the rendered images and the calculated values it is possible to understand the fluctuation of the available light levels over the course of a year. The difference in the results is even more evident when the images are displayed in false colour.


While illuminance simulations calculate the amount of light received on a surface, luminance refers to the light that is reflected off the surface, and therefore visible to us. Luminance images are basically photorealistic renderings that can be used to evaluate light contrast and distribution. In the two images below is a comparison of a simulated luminance image (left) and an actual photo of the space (right).

comparison_A4_300dpi (smaller)

A useful way to evaluate the building’s light levels on a whole is to simulate the luminance (or illuminance) on a cross section view. The following image is an example of a cross section luminance rendering, both in false colour and black-and-white. Just like the daylight factor on the floor plan view, these images make it easier to compare the different parts of the building and determine how natural light is distributed.

section (smaller)

Luminance images are also very useful in showing the variation in light availability and distribution under different sky conditions or during different times of the day. The following images dispaly the luminance levels in one of the bedrooms during a sunny day in March, at 09:00, 12:00 and 15:00 respectively.

Connected_Luminance_March_0900 (smaller)

Connected_Luminance_March_1200 (smaller)

Connected_Luminance_March_1500 (smaller)

Sunlight animation

Finally, an animation of the daylight conditions during the course of a certain day shows the sun path and the light patches it creates in the interior space.