DAYSIM 4.0 plus new web site

Dear colleagues:

In Short

· We have new DAYSIM version (4.0) plus web site. Check it out at

· Andy McNeil from LBNL kindly added a new DAYSIM discussion list to Radiance Online at

For those interested in the details

Apart from offering a download link for the latest DAYSIM version, the new site also offers an interactive API documentation that describe all DAYSIM subprograms and header file keywords<>. Focus users of the site are Daysim expert users who want to go beyond the capabilities of the various DAYSIM GUIs (see below) as well as third party GUI developers who want to implement DAYSIM into their programs. The development of the site was supported by the US Department of Energy Energy-Efficiency HUB<>. (Thank you to all US tax payers among you.) The current DAYSIM development team includes MIT, the Fraunhofer Institute for Solar Energy Systems (ISE) and Penn State University (PSU). With the new version come a few changes and new features.

Given the rising number of DAYSIM GUIs, we decided to phase out the old, rather unattractive JAVA GUI that came with the old Daysim and instead rely on third parties to develop plug-ins. In case you are still interested in using the old GUI, you can still download Daysim 3.1e from the new web site. DAYSIM GUIs that I am aware are listed below. If your GUI is missing or if the table below misrepresents a software, please let me know.

Table 1. Overview of DAYSIM Plug-in Capabilities








Climate-based Illuminance Metrics

Annual Glare Analysis

Electric Lighting Control

Electric lighting Systems (IES files)

Photo Sensor Placement

#Modified JAVA GUI developed by Rick Mistrick at Penn State.

Annual Glare Analysis
Daysim 4.0 includes and improved, more robust version of gen_dgp_profile<> written by Jan Wienold (ISE). The program calculates annual daylight glare probabilities profiles at selected view points within a scene based on a Radiance scene file, a Radiance View File and an epw weather file.

With support from SAGE Electrochromic we implemented the capability to model show shading groups independently in Daysim. This allows users to model a variety of rather complicated dynamic facades<>.

Electric Lighting
The shading module can be integrated with various electric lighting controls. Rick Mistrick (PSU) is currently expanding the list of supported controls. PSU is also working on a new DAYSIM program that allows to explicitly model and control electric light sources using IES files. There will also be a module that supports the placement of photo sensors within a scene. We expect these new programs to make their way into DAYSIM later this year.

Happy Daylight Simulations,

Christoph Reinhart
Associate Professor
Department of Architecture
Massachusetts Institute of Technology
77 Massachusetts Ave, Rm 5-418, Cambridge, MA 02139, USA


t: 617 253 7714, f: 617 253 6152, [email protected]<mailto:[email protected]>