DAYSIM (Dynamic Daylight Simulations)

DAYSIM is a daylighting analysis software that calculates the annual daylight availability in arbitrary buildings as well as the lighting energy use of automated lighting controls (occupancy sensors, photocells) compared to standard on/off switches. Among the dynamic daylight performance metrics calculated by Daysim are daylight autonomy and useful daylight index.

Technical Background

Daysim combines the backward raytracing software Radiance, developed by Greg Ward at the Lawrence Berkeley National Laboratory, with a daylight coefficients approach. The underlying sky model to calculate annual illuminance profiles is the Perez all weather sky model. A stochastic model from Skartveit and Olseth has been adapted to mimic the short-time-step dynamics of indoor illuminances based on hourly mean direct and diffuse irradiances. Annual illuminance profiles are coupled with user occupancy data to predict the annual use of electric lighting in a building zone depending on the lighting and blind control strategy. The underlying Lightswitch manual lighting control model is based on monitored occupancy behaviour from several field studies.

Daysim and Ecotect

Daysim has been linked to the popular Ecotect building design software. Ecotect models can be directly exported to Daysim for further analysis. Vice versa, Daysim results can be imported back into Ecotect for presentation. An example daylight autonomy distribution calculated using Daysim and visualized through Ectoect is shown below.

Getting started

The fastest way to start using DAYSIM is to download the installation files for Windows 2000 or Linux/Unix and work through the Getting Started and DAYSIM Tutorial documents.

Publications

Findings from a survey on the current use of daylight simulations in building design
Reinhart, C.F. Fitz, A.
Energy and Buildings, 38 (7)
pp. 824-835. 2006-07-01
[Full citation / Référence complète]

Development and validation of a radiance model for a translucent panel
Reinhart, C.F. Andersen, M.
Energy and Buildings, 38 (7)
pp. 890-904. 2006-07-01
[Full citation / Référence complète]

Dynamic daylight performance metrics for sustainable building design
Reinhart, C.F. Mardaljevic, J. Rogers, Z.
Leukos, 3 (1)
pp. 1-25. 2006-07-01
[Full citation / Référence complète]

Electric lighting energy savings for a photocell controlled dimmer - a comparative simulation study using DOE.2 and Lightswitch Wizard
Reinhart, C.F. Jones, C.
Proceedings of the ESIM 2004 Conference (Vancouver, 2004-06-10)
pp. 183-189. 2004-06-01
[Full citation / Référence complète]

Lightswitch- 2002: a model for manual and automated control of electric lighting and blinds
Reinhart, C.F.
Solar Energy, 77 (1)
pp. 15-28. 2004-06-01
[Full citation / Référence complète]

Monitoring manual control of electric lighting and blinds
Reinhart, C.F. Voss, K.
Lighting Research & Technology, 35 (3)
pp. 243-260. 2003-08-01
[Full citation / Référence complète]

Dynamic annual daylight simulations based on one-hour and one-minute means of irradiance data
Walkenhorst, O. Luther, J. Reinhart, C.F. Timmer, J.
Solar Energy, 72 (5)
pp. 385-395. 2002-05-01
[Full citation / Référence complète]

Acknowledgement

DAYSIM has been developed at the Lighting Group of the National Research Council Canada and at the Solar Building Design Group of the Fraunhofer Institute for Solar Energy Systems. The overall development of DAYSIM has been coordinated by Christoph Reinhart since 1997. The individual simulation modules within DAYSIM were developed by the following individuals:

• DAYSIM's dynamic daylight simulation module to simulate annual illuminance profiles was developed and implemented by Christoph Reinhart at the Fraunhofer Institute for Solar Energy Systems (Aug 1998 to Jan 2001).
• The DAYSIM subprogram to model the short-time step dynamics on indoor illuminances was developed and implemented by Oliver Walkenhorst at the Fraunhofer Institute for Solar Energy Systems (Oct 1999 - Apr 2001).
• The manual lighting control model Lightswitch and the stochastic user occupancy model were developed by Christoph Reinhart at the National Research Council Canada (Feb 2001 - August 2003).
• DAYSIM's graphical user interface was programmed in JAVA at the National Research Council Canada by the Prashant Jois (Jan 2003 - Apr 2003) and Melissa Morrison (May 2003 - Aug 2003).
• A modified version of the RADIANCE program rtrace that calculates a set of daylight coefficients using either the traditional RADIANCE approach or Roland Schregle PhotonMap forward raytracer was programmed by Augustinus Topor at the Fraunhofer Institute for Solar Energy Systems (Mar 2003 to July 2003).
• Recommended illuminance levels and maximum lighting power densities have been added to the documentation by Annegret Fitz (Oct 2003 to Mar 2004).
• Getting Started document has been written by Guido Petinelli to help simulation newcomers getting started with Ecotect/Radiance/Daysim (July to September 2006).

Related Information

DAYSIM End User License Agreement

Daysim - Download

DAYSIM Download

Institutes:

• NRC Institute for Research in Construction