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A sufficient supply with daylight and an adequate visual connection to the outside are essential requirements both for the well-being and for the motivation of people who reside in buildings. The required lighting levels can be fulfilled by artificial light, daylight, or a combination of both.

The calculation of daylight occurs in DIALux evo using three different sky models, which are described in the CIE 110-1994:

  • overcast sky
  • average sky
  • clear sky

The daylight quotient, required in some standards, can only be calculated with a cloudy sky. DIALux evo automatically creates a corresponding light scene when you perform a daylight calculation. Direct sunlight can be calculated only in clear or average sky.

The calculation of the illumination takes place only in the interior and only by daylight relevant windows, which conduct the daylight inside the building. Other building openings are not considered in the calculation of daylight. Windows that are inside the building are not relevant for daylight. In most cases DIALux automatically detects this. If necessary, you can change this setting at the window in the apertures tool.

Outside the building the scene is only enlighted for visualization. Illumination levels are not calculated.

Location and North alignment

You can arrange the location along with the building in the site tool in the construction mode.


You can either select a location directly from the list or enter yourself latitude and longitude. With the action “drawing north arrow” you can change the orientation of your building. Simply draw the arrow in the 2D floor plan of your scenes.

The north arrow drawing function only works in the site
Alternatively, you can enter the northern alignment directly as a
degree value.

Calculating with daylight - Creating a daylight scene

To calculate daylight with DIALux evo, create a corresponding light scene. You can find the appropriate tool in the light mode.
To create a daylight scene select another sky model as "No daylight" in the light secene tool.
In combination with a window in your project, DIALux evo recognizes a daylight scene, what you also see because the "start calculation" button is activated.


Here you can select the desired CIE sky model, select the date and time, and if necessary, enable the option "Direct sunlight".

The option of direct sunlight is available only if you have not
selected the overcast sky.

It is up to you whether you want to include artificial light in the calculation of daylight. For a pure daylight scene you must remove all lighting groups from the light scene or fade down all the lights to 0% dimming value. You can create any number of lighting scenes with or without artificial light, each differing in the date, time and sky model.

If you need the results in the outputs please do not forget to activate the "generate outputs for this light scene" setting.


Once you create a light scene with daylight, there will be
automatically crated another light scene “Light scene for the energy
rating”. In this automatically generated light scene, the sky model "overcast"
is always selected. This lights scene is required to display a daylight quotient in the


The Outputs for daylight scenes do not need special settings. In addition to the light technical results they contains only information about the place, date time, sky and zenith luminance. In the space summary a daylight quotient is always given.


Daylight with daylight control systems and skylights

From DIALux evo 6 onwards it is possible for the designer to plan real daylight control systems, skylights and façade elements into his daylight calculation.
In the photorealistic visualization the incidence of sunlight and shadows can be seen at a glance and evaluated.


This includes vertical louvre blinds and textile blinds, skylights, foils and prismatic systems.
Several light control elements may be placed and configured on top of each other on windows.
The daylight quotient and illuminance within the building are defined, depending on the date, the time, the alignment of the building and the sky conditions.


To configure the products a whole new tool is now available for daylight control systems.
Here you can set the site of the lighting installation, the motion /status of movement of window fittings, control strategies and the angle.
Systems which have already been configured can quite easily be transferred to other windows.


In addition to rectangular roof windows DIALux now simulates domes, skylights and continuous roof lights for which photometric parameters have been measured.


The electronic catalogues of reputable manufacturers for sunshade and daylight control systems are available for selection of products.
The catalogue selection can be specially filtered to show suppliers of daylight-relevant products.
Alternatively, you can import product data via the open daylight system ODLS - format or the DIALux DDLS format.
These contain images and product descriptions and all the technical data required for light calculation.
All the calculation results can be viewed in the result overview and in the product documentation.
In addition, there is a documentation of the daylight situation and detailed product descriptions.
The light control properties can be seen at a glance with the help of the new hemispheric transmission diagram.

General information

From version 6 onwards the influence of skylights can be simulated and taken into consideration in the calculation of daylight scenes.
Real, physically measured products are used for which individual catalogues are available.
DIALux evo now employs a new calculation procedure which was developed in cooperation with the Frauenhofer Institute for Building Physics.
This is different from other light simulations in that the calculation of the daylight control systems is not via ray tracing.
The photometric properties of the products are subjected to physical measurement; and the influence of both the daylight situation and of the products on each other is defined algorithmically.
Thus a fast and accurate calculation of the whole scene is possible.

Product types

  • Louvre blinds

Louvre blinds are mobile or fixed daylight control systems which consist of horizontal or vertical ribs.
There are systems for use within buildings or on the façade or both. They are mostly used to protect from direct sunlight and to steer indirect light into the interior of the building.
They are controlled manually or are set to move automatically according to the sun.

  • Blinds

Blinds are systems for darkening a room or are used as sun protection. They are mostly used inside buildings, but there are also systems for outdoor applications.

  • Foils

Foils are placed directly on the window pane. They are used for UV protection, as privacy shields or, if they include microstructures, also have light controlling properties.

  • Skylights

Light domes or continuous roof lights can be used as skylights in DIALux. Light domes have firmly prescribed dimensions.
Continuous roof lights can be scaled within predefined limits. Skylights perforate the shell of the building just like windows.
They are automatically adjusted to the incline of the roof and cut into the surface of the roof at right angles. Skylights can be rotated by the user.
However, the user must ensure that no further apertures are formed where the skylight adjoins the surface of the roof.

  • Material for roof windows

In DIALux it is not possible to mount new layers with sun shades and daylight control systems on skylights as with windows.
Standard roof windows can however be fitted with additional materials as can windows.
So special forms of roof windows, e.g. roof windows in old projects can later be furnished with light control properties.

  • Prismatic systems

Light directing filters are static systems, not adjustable systems, which can be fitted in the cavity between the glass panels or directly on the window pane.
With the aid of specially formed profiles or structures it is possible to direct the sunlight selectively into the interior of the building.

  • Self-rotating prismatic systems

This special type of light directing filter has a mirrored micro-louvre structure which is rotated according to the alignment of the building and the angle of the roof.
The direct incidence of sunlight is thus kept to a minimum. The alignment is set once when the light directing filter is manufactured.
This is therefore also a non-dynamic system. The optimal alignment of self-rotating light directing filters is carried out automatically in DIALux.
Later adjustment of the rotation by the user is not possible.


Calculating with daylight control systems is subject to certain limitations which the designer must take into consideration and to which we would now like to draw your attention:

  • Calculation time

When calculating with daylight and daylight control systems, the building apertures are divided into small areas.
The division takes place according to the situation and depends on the size, the construction and the system used.
A light distribution curve is calculated for each of the small areas. So the calculation time is longer for many large windows with many daylight control systems.

  • Outdoor areas

Calculation is only for the interior of the building. No conclusions can be drawn about the daylight conditions outside.
For this reason the sky is shown as black when a ray tracer is used.
For calculation the ray tracer uses luminance ( light density) values which cannot be calculated in areas of daylight outside.

  • Inner courtyards

At present DIALux evo is not able to recognize windows opening onto a courtyard as relevant for daylight. The daylight entering from a courtyard cannot be calculated.

  • Visualization

Skylights are displayed with highly simplified geometry. The angle at which the ribs are positioned is not shown in the visualization but the photometric calculation is correct.

  • Standardized skies

Calculation takes place on the basis of standardized skies as described in CIE 110-1994 „Spatial Distribution of Daylight – Luminance distributions of various reference skies“
Overcast sky, partially overcast sky, clear sky. A luminance (light density) is allocated to each point of the sky.
The luminance depends on the angle of altitude of the sun, the solar azimuth and the zenith and the azimuth of the sky.
The calculation of photometric values using standardized skies may deviate from the actual values on site.

  • Quantity of sun shade and daylight control systems

Because of the calculation algorithms used is only possible to calculate façade elements up to a thickness of 0.4 m.
DIALux evo calculates a maximum of four layers of sunshade and light control systems.

Working with sun shade and daylight control systems

A prerequisite for planning sun protection and daylight control systems are building apertures such as windows
and roof windows as well as at least one light scene with active daylight calculation.
Daylight calculation is activated by selecting a sky in the appropriate light scene.



You obtain product data in the form of ODLS files from the manufacturer of the daylight control system.
Activating "Load daylight system" opens the file dialogue. After loading an ODLS file you must allocate a product type (louvre blind, blind, foil, prismatic system, material for roof window)
to the product you have selected.
You can optionally install the electronic catalogue. The catalogue provides a detailed presentation of the product and is of great assistance in searching for products.




In the mode "Construction" you will find the tool "Façade elements".

Under "Active façade element" you will find a product image, the name of the façade element selected and a manufacturer logo.
Via "Select" you can access the façade elements last used, your personal favourites or the catalogues installed.
In "Manufacturer" mode you will find the catalogues or the source from which you can obtain the catalogues.


  • Placing façade elements

To position a facade element you first select a window in CAD by activating "Add façade element".


add a new layer to the window selected. You will find it again under "Layer configuration".
Please check the position of the façade element (inside or outside) and the distance from the window pane which is already there.



You can change the order directly with the mouse or by using the two arrows. You can configure up to four layers per window.

  • Layer properties

Here you can change the properties of the individual layers, e.g. the position of a textile blind or the angle of a louvre blind system.
Not all products have position status, e.g. foils. The position status can be entered as a value in percent for whole window pane,
as an absolute value in metres, or with the aid of the slide bar.



  • Calculation

As with artificial light and previous calculation of daylight, calculation is via the buttons "Start calculation" or "Continue calculation".


  • Outputs

Under output you will find two separate outputs for daylight control systems

  • Product data sheets

On the product data sheets for sun protection and daylight control systems you will find not only images,
a description and the product dimensions but also a hemispheric transmission diagram.
Depending on the incidence of light, this shows the transmission of a product in percent.
For each configurable product there is a separate diagram depending on the sets of measured data.



  • Daylight systems

The output "Daylight systems" shows the position and the layer configuration of the individual daylight systems.
In the settings on the side you can set the types of daylight in the output.