modeling hourly daylight illuminance/daylight factor values for a year

Hi all,

I ask this question with a very basic knowledge of radiance's functioning so
excuse me if the question is not framed well.

Is it possible to program/loop radiance modeling to produce daylight
illuminance or daylight factor values at various points on a work surface of
a space for each hour through the year? (24x365 = 8760 values for a point on
a work plane)

If any, what are the constraints to such a process and how can they be
overcome so as not to model each hour individually?

I am using Radiance on Cygwin.

Thanks in advance,


Venkata Ramana Koti
MS in Building Design (Energy/Climate)
School of Architecture and Landscape Architecture
College of Design
Arizona State University, Tempe AZ 85287


A brute-force approach (i.e. a new simulation for every hour) can be done, but it is computationally very inefficient. A better approach is to use daylight coefficients. Background, theory and implementation are described in chapter 6 here:
[Web pages seem to be down at the moment - try again later/tomorrow]

An end-user DC version called DAYSIM is available from here:
DAYSIM is different in detail from the description noted above, but does more or less the same thing.



Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]