Daylighting Calculations for LEED

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Hi All,

What program do you use to complete the daylighting calculations for LEED
IEQ Credit 8.1 using the simulation method?



No Username provide's picture
Joined: 2011-09-30
Reputation: 200

Hi Karen,

I usually use Ecotect with Radiance Engine, but I did once with Lumen



eddy santosa's picture
Joined: 2011-10-02
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We have been using Daysim for the past few projects.

Umesh Atre's picture
Joined: 2011-09-30
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I regularly use AGI32 for any daylighting studies, though I've not yet
been involved in a project where that credit was not handled by the
non-photometric options of documenting compliance.

Here's a quick writeup describing how you can use AGI32 to handle the
daylight factor grids for LEED 2.1 and 2009:


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805

I ran into limitations with the USGBC's other compliance demonstration
methods all the time at my last job; the so-called glazing factor
spreadsheet can only deal with very basic space types. I always used
Radiance for my simulation-based documentation, because it's what I'm
familiar with. But folks here have mentioned the other popular ones. Any
lighting simulation software that includes a daylight simulation component
will likely work, as long as you can set up grids and define standard CIE
clear and overcast sky types (depending on which compliance path you're
using). Lumen Designer is no longer commercially available, but as
mentioned, AGI32, Radiance, and also 3DStudio Max Design can all be used
for these types of simulations when the spreadsheet the USGBC provides
falls short. DiaLux is a freely available (Windows) program that
incorporates daylighting calculations as well:

- Rob Guglielmetti

Rob Guglielmetti's picture
Joined: 2011-10-02
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Thanks for the heads up, this looks like something worth looking into.
How was the learning curve with the program? And are high quality
renderings fairly simple to produce if you have a dxf file? They have
some nice photo-quality renderings on their website, but it'd be nice to
hear that it doesn't require gobs of time to produce.

Karen, we currently use Rayfront, and I think it takes some workarounds
to produce LEED documentation. I haven't personally used it, and I think
it has a pretty steep learning curve. On the other hand, it does
produce some very nice renderings...If only reviewers appreciated pretty
pictures J


Eric O'Neill's picture
Joined: 2011-09-30
Reputation: 0

IES is perfect for daylight calculations and it's approved for the
Daylighting credit.
I am a former IES consultant and worked for them for a few years so have
carried out many such simulations along with LEED analysis and dynamic

I'm currently working as a building analyst in Vancouver and use the
software for LEED analysis here too.

On Fri, Feb 12, 2010 at 13:33, Eric O'Neill wrote:


Chris2's picture
Joined: 2011-10-02
Reputation: 400

I would not characterize AGI32 as a "pretty rendering" generator - there
are more efficient and appropriate tools for that purpose. I'm a critic
first, and don't like to speak glowingly of any program, but AGI32 is
best characterized as one of the more sophisticated photometric software
solutions among the other options, with a correspondingly difficult
learning curve...

While I am proficient in AGI32 I do the bulk of my photometric work with
Visual, as it's what I'm fastest with.

I do utilize AGI32 for photometrics/renderings/daylight work when I'm
(A) working photometrics from a Sketchup model - as I've worked out how
to move Sketchup into AGI32, (B) need to perform daylighting calcs or
studies, as Visual doesn't have this component, (C) special/complicated
applications, such as sports pool surface illuminance calcs, or (D)
required to use AGI32 for some extraneous reason. My general aversion
is really only rooted in the (to me) unintuitive UI, which if were all I
ever used would be something I'm sure I could get used to. Again I find
I get simpler work done much faster in Visual if only because it's what
I'm familiar with.

Speaking specifically to daylighting with AGI32 - it could certainly be
easier, but AGI32 produces something I've struggled to achieve with
other packages: accuracy. I can model my office building from my desk,
calculate the solar contributions at the current instant at a specific
point, then walk over and measure the exact same reading. It helps that
I happen to know our actual glazing properties and have a local
calibration factor to apply to standard IES sky models.

Let me offer a caution to you and anyone else seeking to get started
with daylighting studies, however: There will be a learning curve with
any new software, yes, but do not make the mistake of assuming that if
you can operate a software package that you will not need to progress
along an independent learning curve for knowledge in daylighting! After
generating your first believable rendering, it's easy to fall into
thinking you must know what you're doing. Read the IES Handbook to
understand where their standard sky models come from. Read up on the
CIE models as well. Test yourself and measure your results with
existing spaces. There is a lot to learn regarding the properties of
glazing that you probably weren't required to learn for energy
modeling/photometric software. Daylight modeling is a specific skillset
that requires knowledge unique from the average photometric or
energy-modeling pro. Just be careful to not treat it as simply learning
to generate numbers/pictures from another piece of software.

Speaking to another question you brought up: AGI32 does import
Autodesk's dwg/dxf. Turning those into into a high quality (and
accurate) daylight rendering however does not happen at the push of a

PS: If you're just looking to do fast, simply sun angle studies without
interreflections/soft shadows, and the ability to generate a pretty
rendering, I think you'd find the (free) Google Sketchup to be right up
your alley. The pro version offers Autodesk proprietary format support
among a myriad of other formats.

Phew! I'm off for the weekend =). Happy Valentine's everybody!


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805

Hi Karen,

I'm using DIALUX for daylight calculation.
Not too detailed and complicated but enough to comply with LEED Daylight Calculation requirements.

And its also FREE! Technical Support and Product Updates are also available.



reniel barroso's picture
Joined: 2011-09-30
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I used dialux and found it differs compared to Radiance. A better fit
is relux.

Tariq Abbas's picture
Joined: 2011-10-02
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Hi Tariq,

When you say "differed", what exactly do you mean? Dialux is radiosity based (like AGI32 and dear departed Lightscape), whereas Relux uses Radiance as the engine so it's essentially a raytracing-based simulation program. Different simulation algorithms, but both are valid approaches in general. In the general sense, especially in the context of documenting LEED certifications, I think both approaches have merit.

- Rob Guglielmetti

Rob Guglielmetti's picture
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Maybe I was doing something wrong in Dialux, but couldn't for love nor
money get them to match for the same simple setup.

Both are free tools and I got much better agreement with Relux and
Radiance IES than with Dialux.

Tariq Abbas's picture
Joined: 2011-10-02
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On Tue, February 16, 2010 6:47 am, Tariq Abbas wrote:

Interesting. Of course both programs approach light transport simulation
differently and they each have different capabilities in that regard. It's
possible that one of your simulations either taxed one of the algorithms
to the brink, or that you didn't exercise the options enough.

Agreement with what? The implication here is that you had some real
world[TM] data that you were comparing to your simulations, which is very
interesting to me. Is this the case? Did you have some sort of benchmark
data that you were measuring against? If it was a case of comparing two
simulations, I'm afraid it will always be apples and oranges. But I'd be
interested in learning more about what your test was all about!

- Rob Guglielmetti

Rob Guglielmetti's picture
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