Hi,
I am aware that there seem to be questions in the LEED simulation requirements which simply have no obvious solution. However, I am curious how people are actually still finding a way to work around.
What are you actually using as a sky model for simulations aiming at LEED? Just the output of gensky clear without sun? Some available irradiance weather data for the given march / september days as an input for gensky? Anything else?
Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972
jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic
Hi John,
I am aware of that really nice overview. The critique of using an impossible sky model is hard to question. Excluding the sun also means that any technique to make use of direct sunlight by e.g. redirecting it deeper from the perimeter into the building is not accounted for at all. So that is why I was wondering how folks doing their real-life jobs for LEED are handling the problem with the current standards in mind.
Another question is whether direct sunlight, after it got redirected, is still direct sunlight in LEED terms.... or whether redirected means indirect here and I could again include it... leaving me with a more meaningful sky model (clear sky with sun, and only portions directly entering the used spaces being locked out assuming users would block them by sunshades) accounting for redirecting facades.
I am not sure wether this is too much LEED-specific for the mailing list, but I was really curious how Radiance folks is working around the not-so-physically-based specifications of current LEED when setting up simulations.
Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic
Lars,
I have done several LEED compliance calculations in the past using clear
sky with sun (+s as the gensky parameter). This allows for daylight
redirecting devices to push light further into a space, and more
recently the requirement for glare control above 500fc.
My take is that the phrase "clear sky" does not mean "clear sky without
sun" as might be mistaken in general radiance terms. I've always assumed
the sun is included.
None of our submitted calculations have been questioned to date, so
assume that this is acceptable.
Hope this helps!
Cheers.
Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025
Direct: 212.616.0254
Email: chris.coulter@burohappold.com
Website: www.burohappold.com
-----Original Message-----
From: Lars O. Grobe [mailto:grobe@gmx.net]
Sent: Tuesday, June 19, 2012 4:21 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Current practice for LEED sky modelling?
Hi John,
I am aware of that really nice overview. The critique of using an
impossible sky model is hard to question. Excluding the sun also means
that any technique to make use of direct sunlight by e.g. redirecting
it deeper from the perimeter into the building is not accounted for at
all. So that is why I was wondering how folks doing their real-life jobs
for LEED are handling the problem with the current standards in mind.
Another question is whether direct sunlight, after it got redirected, is
still direct sunlight in LEED terms.... or whether redirected means
indirect here and I could again include it... leaving me with a more
meaningful sky model (clear sky with sun, and only portions directly
entering the used spaces being locked out assuming users would block
them by sunshades) accounting for redirecting facades.
I am not sure wether this is too much LEED-specific for the mailing
list, but I was really curious how Radiance folks is working around the
not-so-physically-based specifications of current LEED when setting up
simulations.
Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes
here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development De Montfort
University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic
_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Yeah, the LEED "clear sky" absolutely means a clear sky with a sun (unless
they've changed it recently in LEED). ALL of my clear sky simulations with
Lightscape, AGi32, and Radiance over the years have included the sun.
After all, aren't we trying to predict daylight performance??
Hey Chris, when'd you move to New York? Congrats, and enjoy the humidity.
=8-)
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.gov
On 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com> wrote:
Lars,
I have done several LEED compliance calculations in the past using clear
sky with sun (+s as the gensky parameter). This allows for daylight
redirecting devices to push light further into a space, and more
recently the requirement for glare control above 500fc.My take is that the phrase "clear sky" does not mean "clear sky without
sun" as might be mistaken in general radiance terms. I've always assumed
the sun is included.None of our submitted calculations have been questioned to date, so
assume that this is acceptable.
Hope this helps!Cheers.
Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025
Direct: 212.616.0254
Email: chris.coulter@burohappold.com
Website: www.burohappold.com-----Original Message-----
From: Lars O. Grobe [mailto:grobe@gmx.net]
Sent: Tuesday, June 19, 2012 4:21 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Current practice for LEED sky modelling?Hi John,
I am aware of that really nice overview. The critique of using an
impossible sky model is hard to question. Excluding the sun also means
that any technique to make use of direct sunlight by e.g. redirecting
it deeper from the perimeter into the building is not accounted for at
all. So that is why I was wondering how folks doing their real-life jobs
for LEED are handling the problem with the current standards in mind.Another question is whether direct sunlight, after it got redirected, is
still direct sunlight in LEED terms.... or whether redirected means
indirect here and I could again include it... leaving me with a more
meaningful sky model (clear sky with sun, and only portions directly
entering the used spaces being locked out assuming users would block
them by sunshades) accounting for redirecting facades.I am not sure wether this is too much LEED-specific for the mailing
list, but I was really curious how Radiance folks is working around the
not-so-physically-based specifications of current LEED when setting up
simulations.Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes
here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development De Montfort
University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Hi Chris, Rob, so what are you using as sun luminance? Some average from weather data? A theoretical value from a model? John's examples are a great demonstration for the problem. I am rather sure that an invalid assumption for the direct sun in a sky model would by far outnumber the effect of changing a sky distribution to whatever model. Is there common sense that if "clear sky" is referenced, I should use the CIE clear sky without any modification, just as what I get from gensky? Or should I feed in at least an illuminance reading either from my own measurement or from weather data?
Cheers, Lars.
--
Dipl.-Ing. Architect Lars O. Grobe
On Jun 19, 2012, at 17:59, "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov> wrote:
Yeah, the LEED "clear sky" absolutely means a clear sky with a sun (unless
they've changed it recently in LEED). ALL of my clear sky simulations with
Lightscape, AGi32, and Radiance over the years have included the sun.
After all, aren't we trying to predict daylight performance??Hey Chris, when'd you move to New York? Congrats, and enjoy the humidity.
=8-)Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.govOn 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com> wrote:
Lars,
I have done several LEED compliance calculations in the past using clear
sky with sun (+s as the gensky parameter). This allows for daylight
redirecting devices to push light further into a space, and more
recently the requirement for glare control above 500fc.My take is that the phrase "clear sky" does not mean "clear sky without
sun" as might be mistaken in general radiance terms. I've always assumed
the sun is included.None of our submitted calculations have been questioned to date, so
assume that this is acceptable.
Hope this helps!Cheers.
Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025
Direct: 212.616.0254
Email: chris.coulter@burohappold.com
Website: www.burohappold.com-----Original Message-----
From: Lars O. Grobe [mailto:grobe@gmx.net]
Sent: Tuesday, June 19, 2012 4:21 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Current practice for LEED sky modelling?Hi John,
I am aware of that really nice overview. The critique of using an
impossible sky model is hard to question. Excluding the sun also means
that any technique to make use of direct sunlight by e.g. redirecting
it deeper from the perimeter into the building is not accounted for at
all. So that is why I was wondering how folks doing their real-life jobs
for LEED are handling the problem with the current standards in mind.Another question is whether direct sunlight, after it got redirected, is
still direct sunlight in LEED terms.... or whether redirected means
indirect here and I could again include it... leaving me with a more
meaningful sky model (clear sky with sun, and only portions directly
entering the used spaces being locked out assuming users would block
them by sunshades) accounting for redirecting facades.I am not sure wether this is too much LEED-specific for the mailing
list, but I was really curious how Radiance folks is working around the
not-so-physically-based specifications of current LEED when setting up
simulations.Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes
here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development De Montfort
University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Yeah, the sun luminance and solar disc size is based on Greg's
implementation of the CIE standard sky model in gensky. The Perez sky
model has been shown to have problems with low sun angles but does a nice
job otherwise, when given weather info (e.g. TMY, EPW).
The problem of course comes when you want to use these sky models in a
daylight coefficient approach, where the sun's luminance is spread around
the three nearest patches to the actual solar location. The Tregenza
subdivisions are way too big to make for accurate estimations. This is why
Reinhart and Bourgeois proposed the finer resolutions you get when you use
the -M:2 or -M:4 options in rtcontrib. -M:4 gives you over 2000 sky
patches instead of the original 145 proposed by Tregenza. Greg, Andy, Rick
Mistrick and Eleanor Lee covered this nicely in a paper a couple years ago
at the IES conference.
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.gov
On 6/19/12 9:41 AM, "Lars O. Grobe" <grobe@gmx.net> wrote:
Hi Chris, Rob, so what are you using as sun luminance? Some average from
weather data? A theoretical value from a model? John's examples are a
great demonstration for the problem. I am rather sure that an invalid
assumption for the direct sun in a sky model would by far outnumber the
effect of changing a sky distribution to whatever model. Is there common
sense that if "clear sky" is referenced, I should use the CIE clear sky
without any modification, just as what I get from gensky? Or should I
feed in at least an illuminance reading either from my own measurement or
from weather data?Cheers, Lars.
--
Dipl.-Ing. Architect Lars O. GrobeOn Jun 19, 2012, at 17:59, "Guglielmetti, Robert" ><Robert.Guglielmetti@nrel.gov> wrote:
Yeah, the LEED "clear sky" absolutely means a clear sky with a sun
(unless
they've changed it recently in LEED). ALL of my clear sky simulations
with
Lightscape, AGi32, and Radiance over the years have included the sun.
After all, aren't we trying to predict daylight performance??Hey Chris, when'd you move to New York? Congrats, and enjoy the
humidity.
=8-)Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.govOn 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com> >>wrote:
Lars,
I have done several LEED compliance calculations in the past using
clear
sky with sun (+s as the gensky parameter). This allows for daylight
redirecting devices to push light further into a space, and more
recently the requirement for glare control above 500fc.My take is that the phrase "clear sky" does not mean "clear sky without
sun" as might be mistaken in general radiance terms. I've always
assumed
the sun is included.None of our submitted calculations have been questioned to date, so
assume that this is acceptable.
Hope this helps!Cheers.
Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025
Direct: 212.616.0254
Email: chris.coulter@burohappold.com
Website: www.burohappold.com-----Original Message-----
From: Lars O. Grobe [mailto:grobe@gmx.net]
Sent: Tuesday, June 19, 2012 4:21 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Current practice for LEED sky
modelling?Hi John,
I am aware of that really nice overview. The critique of using an
impossible sky model is hard to question. Excluding the sun also means
that any technique to make use of direct sunlight by e.g. redirecting
it deeper from the perimeter into the building is not accounted for at
all. So that is why I was wondering how folks doing their real-life
jobs
for LEED are handling the problem with the current standards in mind.Another question is whether direct sunlight, after it got redirected,
is
still direct sunlight in LEED terms.... or whether redirected means
indirect here and I could again include it... leaving me with a more
meaningful sky model (clear sky with sun, and only portions directly
entering the used spaces being locked out assuming users would block
them by sunshades) accounting for redirecting facades.I am not sure wether this is too much LEED-specific for the mailing
list, but I was really curious how Radiance folks is working around the
not-so-physically-based specifications of current LEED when setting up
simulations.Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes
here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development De Montfort
University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972jm@dmu.ac.uk
http://www.iesd.dmu.ac.uk/~jm
http://dmu.academia.edu/JohnMardaljevic_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Hi, just add to Robert's comments:
The journal paper based on the IES paper as mentioned by Robert:
Ward, G., Mistrick, R., Lee, E. S., McNeil, A., & Jonsson, J. (2011).
Simulating the Daylight Performance of Complex Fenestration Systems Using
Bidirectional Scattering Distribution Functions within Radiance. Journal of
the Illuminating Engineering Society of North America (Leukos), 7(4).
Another paper by Andy on related topic:
McNeil, A. (2011). The Three-Phase Method for Simulating Complex
Fenestration with Radiance, from
http://radiance-online.lbl.gov:82/learning/tutorials/three-phase-method-tutorial
- Cheers, Ji
On Wed, Jun 20, 2012 at 12:02 AM, Guglielmetti, Robert < Robert.Guglielmetti@nrel.gov> wrote:
Yeah, the sun luminance and solar disc size is based on Greg's
implementation of the CIE standard sky model in gensky. The Perez sky
model has been shown to have problems with low sun angles but does a nice
job otherwise, when given weather info (e.g. TMY, EPW).The problem of course comes when you want to use these sky models in a
daylight coefficient approach, where the sun's luminance is spread around
the three nearest patches to the actual solar location. The Tregenza
subdivisions are way too big to make for accurate estimations. This is why
Reinhart and Bourgeois proposed the finer resolutions you get when you use
the -M:2 or -M:4 options in rtcontrib. -M:4 gives you over 2000 sky
patches instead of the original 145 proposed by Tregenza. Greg, Andy, Rick
Mistrick and Eleanor Lee covered this nicely in a paper a couple years ago
at the IES conference.Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.govOn 6/19/12 9:41 AM, "Lars O. Grobe" <grobe@gmx.net> wrote:
>Hi Chris, Rob, so what are you using as sun luminance? Some average from
>weather data? A theoretical value from a model? John's examples are a
>great demonstration for the problem. I am rather sure that an invalid
>assumption for the direct sun in a sky model would by far outnumber the
>effect of changing a sky distribution to whatever model. Is there common
>sense that if "clear sky" is referenced, I should use the CIE clear sky
>without any modification, just as what I get from gensky? Or should I
>feed in at least an illuminance reading either from my own measurement or
>from weather data?
>
>Cheers, Lars.
>--
>Dipl.-Ing. Architect Lars O. Grobe
>
>On Jun 19, 2012, at 17:59, "Guglielmetti, Robert" > ><Robert.Guglielmetti@nrel.gov> wrote:
>
>> Yeah, the LEED "clear sky" absolutely means a clear sky with a sun
>>(unless
>> they've changed it recently in LEED). ALL of my clear sky simulations
>>with
>> Lightscape, AGi32, and Radiance over the years have included the sun.
>> After all, aren't we trying to predict daylight performance??
>>
>> Hey Chris, when'd you move to New York? Congrats, and enjoy the
>>humidity.
>> =8-)
>>
>>
>> Rob Guglielmetti IESNA, LEED AP
>> Commercial Buildings Research Group
>> National Renewable Energy Laboratory
>> 15013 Denver West Parkway MS:RSF202
>> Golden, CO 80401
>> 303.275.4319
>> robert.guglielmetti@nrel.gov
>>
>>
>>
>>
>>
>> On 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com> > >>wrote:
>>
>>> Lars,
>>>
>>> I have done several LEED compliance calculations in the past using
>>>clear
>>> sky with sun (+s as the gensky parameter). This allows for daylight
>>> redirecting devices to push light further into a space, and more
>>> recently the requirement for glare control above 500fc.
>>>
>>> My take is that the phrase "clear sky" does not mean "clear sky without
>>> sun" as might be mistaken in general radiance terms. I've always
>>>assumed
>>> the sun is included.
>>>
>>> None of our submitted calculations have been questioned to date, so
>>> assume that this is acceptable.
>>> Hope this helps!
>>>
>>> Cheers.
>>>
>>> Chris Coulter
>>> Senior Lighting Designer
>>> Buro Happold Consulting Engineers
>>> 100 Broadway, 23rd Floor
>>> New York, NY 10005
>>> Tel: 212.334.2025
>>> Direct: 212.616.0254
>>> Email: chris.coulter@burohappold.com
>>> Website: www.burohappold.com
>>>
>>> -----Original Message-----
>>> From: Lars O. Grobe [mailto:grobe@gmx.net]
>>> Sent: Tuesday, June 19, 2012 4:21 AM
>>> To: Radiance general discussion
>>> Subject: Re: [Radiance-general] Current practice for LEED sky
>>>modelling?
>>>
>>> Hi John,
>>>
>>> I am aware of that really nice overview. The critique of using an
>>> impossible sky model is hard to question. Excluding the sun also means
>>> that any technique to make use of direct sunlight by e.g. redirecting
>>> it deeper from the perimeter into the building is not accounted for at
>>> all. So that is why I was wondering how folks doing their real-life
>>>jobs
>>> for LEED are handling the problem with the current standards in mind.
>>>
>>> Another question is whether direct sunlight, after it got redirected,
>>>is
>>> still direct sunlight in LEED terms.... or whether redirected means
>>> indirect here and I could again include it... leaving me with a more
>>> meaningful sky model (clear sky with sun, and only portions directly
>>> entering the used spaces being locked out assuming users would block
>>> them by sunshades) accounting for redirecting facades.
>>>
>>> I am not sure wether this is too much LEED-specific for the mailing
>>> list, but I was really curious how Radiance folks is working around the
>>> not-so-physically-based specifications of current LEED when setting up
>>> simulations.
>>>
>>> Cheers, Lars.
>>>
>>>> There's a critique of daylight modelling for LEED and other codes
>>> here:
>>>>
>>>>
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
>>>>
>>>> It includes a discussion on sky models.
>>>>
>>>> Best
>>>> John Mardaljevic
>>>>
>>>> Reader in Daylight Modelling
>>>> Institute of Energy and Sustainable Development De Montfort
>>>> University, The Gateway, Leicester, LE1 9BH, UK
>>>> Tel: +44 (0) 116 257 7972
>>>>
>>>> jm@dmu.ac.uk
>>>> http://www.iesd.dmu.ac.uk/~jm
>>>> http://dmu.academia.edu/JohnMardaljevic
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
>>> Radiance-general@radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>>
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
>>> Radiance-general@radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>
>>
>> _______________________________________________
>> Radiance-general mailing list
>> Radiance-general@radiance-online.org
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>_______________________________________________
>Radiance-general mailing list
>Radiance-general@radiance-online.org
>http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Thanks for doing the legwok, Ji! Here's the other paper I mentioned in that post:
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.gov
Hi, just add to Robert's comments:
The journal paper based on the IES paper as mentioned by Robert:
Ward, G., Mistrick, R., Lee, E. S., McNeil, A., & Jonsson, J. (2011). Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance. Journal of the Illuminating Engineering Society of North America (Leukos), 7(4).
Another paper by Andy on related topic:
McNeil, A. (2011). The Three-Phase Method for Simulating Complex Fenestration with Radiance, from http://radiance-online.lbl.gov:82/learning/tutorials/three-phase-method-tutorial
- Cheers, Ji
Yeah, the sun luminance and solar disc size is based on Greg's
implementation of the CIE standard sky model in gensky. The Perez sky
model has been shown to have problems with low sun angles but does a nice
job otherwise, when given weather info (e.g. TMY, EPW).
The problem of course comes when you want to use these sky models in a
daylight coefficient approach, where the sun's luminance is spread around
the three nearest patches to the actual solar location. The Tregenza
subdivisions are way too big to make for accurate estimations. This is why
Reinhart and Bourgeois proposed the finer resolutions you get when you use
the -M:2 or -M:4 options in rtcontrib. -M:4 gives you over 2000 sky
patches instead of the original 145 proposed by Tregenza. Greg, Andy, Rick
Mistrick and Eleanor Lee covered this nicely in a paper a couple years ago
at the IES conference.
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319<tel:303.275.4319>
robert.guglielmetti@nrel.gov<mailto:robert.guglielmetti@nrel.gov>
On 6/19/12 10:28 AM, "Ji Zhang" <hope.zh@gmail.com<mailto:hope.zh@gmail.com>> wrote:
On Wed, Jun 20, 2012 at 12:02 AM, Guglielmetti, Robert <Robert.Guglielmetti@nrel.gov<mailto:Robert.Guglielmetti@nrel.gov>> wrote:
On 6/19/12 9:41 AM, "Lars O. Grobe" <grobe@gmx.net<mailto:grobe@gmx.net>> wrote:
Hi Chris, Rob, so what are you using as sun luminance? Some average from
weather data? A theoretical value from a model? John's examples are a
great demonstration for the problem. I am rather sure that an invalid
assumption for the direct sun in a sky model would by far outnumber the
effect of changing a sky distribution to whatever model. Is there common
sense that if "clear sky" is referenced, I should use the CIE clear sky
without any modification, just as what I get from gensky? Or should I
feed in at least an illuminance reading either from my own measurement or
from weather data?Cheers, Lars.
--
Dipl.-Ing. Architect Lars O. GrobeOn Jun 19, 2012, at 17:59, "Guglielmetti, Robert" ><Robert.Guglielmetti@nrel.gov<mailto:Robert.Guglielmetti@nrel.gov>> wrote:
Yeah, the LEED "clear sky" absolutely means a clear sky with a sun
(unless
they've changed it recently in LEED). ALL of my clear sky simulations
with
Lightscape, AGi32, and Radiance over the years have included the sun.
After all, aren't we trying to predict daylight performance??Hey Chris, when'd you move to New York? Congrats, and enjoy the
humidity.
=8-)Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319<tel:303.275.4319>
robert.guglielmetti@nrel.gov<mailto:robert.guglielmetti@nrel.gov>On 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com<mailto:Chris.Coulter@burohappold.com>> >>wrote:
Lars,
I have done several LEED compliance calculations in the past using
clear
sky with sun (+s as the gensky parameter). This allows for daylight
redirecting devices to push light further into a space, and more
recently the requirement for glare control above 500fc.My take is that the phrase "clear sky" does not mean "clear sky without
sun" as might be mistaken in general radiance terms. I've always
assumed
the sun is included.None of our submitted calculations have been questioned to date, so
assume that this is acceptable.
Hope this helps!Cheers.
Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025<tel:212.334.2025>
Direct: 212.616.0254<tel:212.616.0254>
Email: chris.coulter@burohappold.com<mailto:chris.coulter@burohappold.com>
Website: www.burohappold.com<http://www.burohappold.com>-----Original Message-----
From: Lars O. Grobe [mailto:grobe@gmx.net<mailto:grobe@gmx.net>]
Sent: Tuesday, June 19, 2012 4:21 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] Current practice for LEED sky
modelling?Hi John,
I am aware of that really nice overview. The critique of using an
impossible sky model is hard to question. Excluding the sun also means
that any technique to make use of direct sunlight by e.g. redirecting
it deeper from the perimeter into the building is not accounted for at
all. So that is why I was wondering how folks doing their real-life
jobs
for LEED are handling the problem with the current standards in mind.Another question is whether direct sunlight, after it got redirected,
is
still direct sunlight in LEED terms.... or whether redirected means
indirect here and I could again include it... leaving me with a more
meaningful sky model (clear sky with sun, and only portions directly
entering the used spaces being locked out assuming users would block
them by sunshades) accounting for redirecting facades.I am not sure wether this is too much LEED-specific for the mailing
list, but I was really curious how Radiance folks is working around the
not-so-physically-based specifications of current LEED when setting up
simulations.Cheers, Lars.
There's a critique of daylight modelling for LEED and other codes
here:
http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance<http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance>
It includes a discussion on sky models.
Best
John MardaljevicReader in Daylight Modelling
Institute of Energy and Sustainable Development De Montfort
University, The Gateway, Leicester, LE1 9BH, UK
Tel: +44 (0) 116 257 7972<tel:%2B44%20%280%29%20116%20257%207972>jm@dmu.ac.uk<mailto:jm@dmu.ac.uk>
http://www.iesd.dmu.ac.uk/~jm<http://www.iesd.dmu.ac.uk/~jm>
http://dmu.academia.edu/JohnMardaljevic_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org<mailto:Radiance-general@radiance-online.org>
http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
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http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
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http://www.radiance-online.org/mailman/listinfo/radiance-general
Lars,
In my understanding, USGBC does not provide the specific guideline for
skymodel. There was a CIR that requested clarification and questioned about
the skymodels (Perez and CIE) and USGBC responded: that "while this CIR
cannot provide any specific rules for selection of the sky model to be
used, both methodologies are acceptable as long as the applicant submits a
narrative explaining the methodology in the submittal.". CIR number for
that one is 9/5/2008 ID# 5148.
I use the same approach as Chris and, not like for energy model, I guess
there is no specific reviewer for daylight credit in the GBCI reviewer
team. I never get any clarification request regarding the simulation
methodology.
Thanks,
Eddy Santosa
Hi Lars, Rob,
From what I understand, gensky produces accurate CIE sky descriptions
according to the older definitions of 3 different sky types (clear, partly
cloudy, and cloudy) - but does not include definitions for the newer CIE
standard that has 15 different sky types derived from 5 different
parameters (A-E). For the older CIE sky types, I am not clear on what
gensky uses to predict the magnitude (zenith luminance, Lz) but from what I
have seen it does not match the methodology that the IESNA lays out for
predicting Lz. With gensky alone I might get around 70,000 lux on a sunny
summer day where as the IESNA guidelines would predict around 100,000lux.
This is the reason I wrote a IES_gensky.py python script, it produces the
same CIE sky distribution functions (adopted by IESNA) but also uses IESNA
guidelines to determine Lz based on some lookup tables. I recall some
babbling from me on this topic around when I developed this:
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001074.html
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001090.html
IES_gensky.py and a corresponding IES_skybright.cal are part of all the
SPOT releases and I would be happy to send them along individually (not
sure I can attach to an e-mail to the group). So I use this script to
define an IESNA standard clear sky with a sun (I agree that although likely
vague in the manual, a sun is supposed to be part of the clear sky calc)
and do my LEED calcs with that sky. When I have looked at weather data and
very clear sky days, the illuminance seems to match this IESNA clear sky
model fairly well.
I have also never had this part of the calc questioned on LEED reviews.
Cheers,
Zack
On Tue, Jun 19, 2012 at 9:41 AM, Lars O. Grobe <grobe@gmx.net> wrote:
Hi Chris, Rob, so what are you using as sun luminance? Some average from
weather data? A theoretical value from a model? John's examples are a great
demonstration for the problem. I am rather sure that an invalid assumption
for the direct sun in a sky model would by far outnumber the effect of
changing a sky distribution to whatever model. Is there common sense that
if "clear sky" is referenced, I should use the CIE clear sky without any
modification, just as what I get from gensky? Or should I feed in at least
an illuminance reading either from my own measurement or from weather data?Cheers, Lars.
--
Dipl.-Ing. Architect Lars O. GrobeOn Jun 19, 2012, at 17:59, "Guglielmetti, Robert" < > Robert.Guglielmetti@nrel.gov> wrote:
> Yeah, the LEED "clear sky" absolutely means a clear sky with a sun
(unless
> they've changed it recently in LEED). ALL of my clear sky simulations
with
> Lightscape, AGi32, and Radiance over the years have included the sun.
> After all, aren't we trying to predict daylight performance??
>
> Hey Chris, when'd you move to New York? Congrats, and enjoy the humidity.
> =8-)
>
>
> Rob Guglielmetti IESNA, LEED AP
> Commercial Buildings Research Group
> National Renewable Energy Laboratory
> 15013 Denver West Parkway MS:RSF202
> Golden, CO 80401
> 303.275.4319
> robert.guglielmetti@nrel.gov
>
>
>
>
>
> On 6/19/12 7:16 AM, "Chris Coulter" <Chris.Coulter@burohappold.com> > wrote:
>
>> Lars,
>>
>> I have done several LEED compliance calculations in the past using clear
>> sky with sun (+s as the gensky parameter). This allows for daylight
>> redirecting devices to push light further into a space, and more
>> recently the requirement for glare control above 500fc.
>>
>> My take is that the phrase "clear sky" does not mean "clear sky without
>> sun" as might be mistaken in general radiance terms. I've always assumed
>> the sun is included.
>>
>> None of our submitted calculations have been questioned to date, so
>> assume that this is acceptable.
>> Hope this helps!
>>
>> Cheers.
>>
>> Chris Coulter
>> Senior Lighting Designer
>> Buro Happold Consulting Engineers
>> 100 Broadway, 23rd Floor
>> New York, NY 10005
>> Tel: 212.334.2025
>> Direct: 212.616.0254
>> Email: chris.coulter@burohappold.com
>> Website: www.burohappold.com
>>
>> -----Original Message-----
>> From: Lars O. Grobe [mailto:grobe@gmx.net]
>> Sent: Tuesday, June 19, 2012 4:21 AM
>> To: Radiance general discussion
>> Subject: Re: [Radiance-general] Current practice for LEED sky modelling?
>>
>> Hi John,
>>
>> I am aware of that really nice overview. The critique of using an
>> impossible sky model is hard to question. Excluding the sun also means
>> that any technique to make use of direct sunlight by e.g. redirecting
>> it deeper from the perimeter into the building is not accounted for at
>> all. So that is why I was wondering how folks doing their real-life jobs
>> for LEED are handling the problem with the current standards in mind.
>>
>> Another question is whether direct sunlight, after it got redirected, is
>> still direct sunlight in LEED terms.... or whether redirected means
>> indirect here and I could again include it... leaving me with a more
>> meaningful sky model (clear sky with sun, and only portions directly
>> entering the used spaces being locked out assuming users would block
>> them by sunshades) accounting for redirecting facades.
>>
>> I am not sure wether this is too much LEED-specific for the mailing
>> list, but I was really curious how Radiance folks is working around the
>> not-so-physically-based specifications of current LEED when setting up
>> simulations.
>>
>> Cheers, Lars.
>>
>>> There's a critique of daylight modelling for LEED and other codes
>> here:
>>>
>>> http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance
>>>
>>> It includes a discussion on sky models.
>>>
>>> Best
>>> John Mardaljevic
>>>
>>> Reader in Daylight Modelling
>>> Institute of Energy and Sustainable Development De Montfort
>>> University, The Gateway, Leicester, LE1 9BH, UK
>>> Tel: +44 (0) 116 257 7972
>>>
>>> jm@dmu.ac.uk
>>> http://www.iesd.dmu.ac.uk/~jm
>>> http://dmu.academia.edu/JohnMardaljevic
>>
>> _______________________________________________
>> Radiance-general mailing list
>> Radiance-general@radiance-online.org
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>
>>
>>
>> _______________________________________________
>> Radiance-general mailing list
>> Radiance-general@radiance-online.org
>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>
> _______________________________________________
> Radiance-general mailing list
> Radiance-general@radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
--
Zack Rogers, P.E., LEED AP BD+C
Daylighting Innovations, LLC
211 North Public Road, Suite 220
Lafayette, CO 80026
(303)946-2310
Hi Lars, Rob,
From what I understand, gensky produces accurate CIE sky descriptions according to the older definitions of 3 different sky types (clear, partly cloudy, and cloudy) - but does not include definitions for the newer CIE standard that has 15 different sky types derived from 5 different parameters (A-E). For the older CIE sky types, I am not clear on what gensky uses to predict the magnitude (zenith luminance, Lz) but from what I have seen it does not match the methodology that the IESNA lays out for predicting Lz. With gensky alone I might get around 70,000 lux on a sunny summer day where as the IESNA guidelines would predict around 100,000lux. This is the reason I wrote a IES_gensky.py python script, it produces the same CIE sky distribution functions (adopted by IESNA) but also uses IESNA guidelines to determine Lz based on some lookup tables. I recall some babbling from me on this topic around when I developed this:
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001074.html
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001090.html
Hi Zack,
It's my understanding that gensky produces sky type 1, which is the standard overcast sky, and sky type 12 for the clear sky from the 15 in the CIE table from 2003. I'm not sure which one it uses for the intermediate sky, nor do I know if it's using the 5 parameter method or something else.
- Rob
On 6/19/12 11:23 AM, "Zack Rogers" <zrogers@daylightinginnovations.com<mailto:zrogers@daylightinginnovations.com>> wrote:
I wish I had more to offer to this conversation. Gensky was written some aeons ago before IESNA updated their standards. I'm not familiar with the later standards, though I probably have them in my files somewhere...
The bottom line is that the zenith luminance calculation in gensky is based on a turbidity & luminance study published back in the 70's (I think) and hasn't been changed. The general assumption was that anyone who cared about absolute levels would input their own zenith value, which is still the recommended practice when working from a weather tape or the the like. Honestly, I didn't realize people were relying on the turbidity-estimated luminance anymore.
I would have no objection to a volunteer updating the zenith luminance calculation in gensky if that's what people want. Adding the new sky types would probably be of even greater interest, though that might exacerbate the already sticky issue of choosing which sky model is appropriate. This is why a general sky model like Perez is usually preferred. I don't really have time to dig into the new standard and sort it all out.
Cheers,
-Greg
From: "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov>
Date: June 19, 2012 10:33:09 AM PDTOn 6/19/12 11:23 AM, "Zack Rogers" <zrogers@daylightinginnovations.com<mailto:zrogers@daylightinginnovations.com>> wrote:
Hi Lars, Rob,
From what I understand, gensky produces accurate CIE sky descriptions according to the older definitions of 3 different sky types (clear, partly cloudy, and cloudy) - but does not include definitions for the newer CIE standard that has 15 different sky types derived from 5 different parameters (A-E). For the older CIE sky types, I am not clear on what gensky uses to predict the magnitude (zenith luminance, Lz) but from what I have seen it does not match the methodology that the IESNA lays out for predicting Lz. With gensky alone I might get around 70,000 lux on a sunny summer day where as the IESNA guidelines would predict around 100,000lux. This is the reason I wrote a IES_gensky.py python script, it produces the same CIE sky distribution functions (adopted by IESNA) but also uses IESNA guidelines to determine Lz based on some lookup tables. I recall some babbling from me on this topic around when I developed this:
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001074.html
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001090.htmlHi Zack,
It's my understanding that gensky produces sky type 1, which is the standard overcast sky, and sky type 12 for the clear sky from the 15 in the CIE table from 2003. I'm not sure which one it uses for the intermediate sky, nor do I know if it's using the 5 parameter method or something else.
- Rob
In our office, we use gensky clear sky model (with sun) but explicitly define the diffuse and direct radiance component using the IESNA methodology, in lieu of the gensky defaults (which I recall Greg saying were not correct).
Zack's python script would be pretty handy for this!
Galen Burrell
Senior Consultant | Arup Lighting
Arup
560 Mission Street Seventh Floor San Francisco CA 94105 United States
t +1 415 957 9445 d +1 415 946 2367
f +1 415 957 9096
www.arup.com/lighting
Message: 3
Date: Tue, 19 Jun 2012 11:33:09 -0600
From: "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov>
To: Radiance general discussion <radiance-general@radiance-online.org>
Subject: Re: [Radiance-general] Current practice for LEED sky
modelling?
Message-ID: <CC0612D0.11881%robert.guglielmetti@nrel.gov>
Content-Type: text/plain; charset="us-ascii"
On 6/19/12 11:23 AM, "Zack Rogers" <zrogers@daylightinginnovations.com<mailto:zrogers@daylightinginnovations.com>> wrote:
Hi Lars, Rob,
From what I understand, gensky produces accurate CIE sky descriptions according to the older definitions of 3 different sky types (clear, partly cloudy, and cloudy) - but does not include definitions for the newer CIE standard that has 15 different sky types derived from 5 different parameters (A-E). For the older CIE sky types, I am not clear on what gensky uses to predict the magnitude (zenith luminance, Lz) but from what I have seen it does not match the methodology that the IESNA lays out for predicting Lz. With gensky alone I might get around 70,000 lux on a sunny summer day where as the IESNA guidelines would predict around 100,000lux. This is the reason I wrote a IES_gensky.py python script, it produces the same CIE sky distribution functions (adopted by IESNA) but also uses IESNA guidelines to determine Lz based on some lookup tables. I recall some babbling from me on this topic around when I developed this:
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001074.html
http://www.radiance-online.org/pipermail/radiance-general/2003-October/001090.html
Hi Zack,
It's my understanding that gensky produces sky type 1, which is the standard overcast sky, and sky type 12 for the clear sky from the 15 in the CIE table from 2003. I'm not sure which one it uses for the intermediate sky, nor do I know if it's using the 5 parameter method or something else.
- Rob
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses
Juicy subject matter. It's be cool if Zacks work could get incorporated
into Radiance. I also agree though that the Perex model is preferred, and
Ian Askdown has written his own version of gendaylight in C++ and
validated it. Only issue there is that his tool puts out data in the way
he wishes to use for his work. There's beed to be some effort writing a
wrapper for the Ashdown_gensky output to be able to use his source in
Radiance, but it's totally open source. Food for thought.
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
15013 Denver West Parkway MS:RSF202
Golden, CO 80401
303.275.4319
robert.guglielmetti@nrel.gov
On 6/19/12 12:20 PM, "Greg Ward" <gregoryjward@gmail.com> wrote:
I wish I had more to offer to this conversation. Gensky was written some
aeons ago before IESNA updated their standards. I'm not familiar with
the later standards, though I probably have them in my files somewhere...The bottom line is that the zenith luminance calculation in gensky is
based on a turbidity & luminance study published back in the 70's (I
think) and hasn't been changed. The general assumption was that anyone
who cared about absolute levels would input their own zenith value, which
is still the recommended practice when working from a weather tape or the
the like. Honestly, I didn't realize people were relying on the
turbidity-estimated luminance anymore.I would have no objection to a volunteer updating the zenith luminance
calculation in gensky if that's what people want. Adding the new sky
types would probably be of even greater interest, though that might
exacerbate the already sticky issue of choosing which sky model is
appropriate. This is why a general sky model like Perez is usually
preferred. I don't really have time to dig into the new standard and
sort it all out.Cheers,
-GregFrom: "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov>
Date: June 19, 2012 10:33:09 AM PDTOn 6/19/12 11:23 AM, "Zack Rogers" >><zrogers@daylightinginnovations.com<mailto:zrogers@daylightinginnovations >>.com>> wrote:
Hi Lars, Rob,
From what I understand, gensky produces accurate CIE sky descriptions
according to the older definitions of 3 different sky types (clear,
partly cloudy, and cloudy) - but does not include definitions for the
newer CIE standard that has 15 different sky types derived from 5
different parameters (A-E). For the older CIE sky types, I am not clear
on what gensky uses to predict the magnitude (zenith luminance, Lz) but
from what I have seen it does not match the methodology that the IESNA
lays out for predicting Lz. With gensky alone I might get around 70,000
lux on a sunny summer day where as the IESNA guidelines would predict
around 100,000lux. This is the reason I wrote a IES_gensky.py python
script, it produces the same CIE sky distribution functions (adopted by
IESNA) but also uses IESNA guidelines to determine Lz based on some
lookup tables. I recall some babbling from me on this topic around when
I developed this:http://www.radiance-online.org/pipermail/radiance-general/2003-October/00
1074.htmlhttp://www.radiance-online.org/pipermail/radiance-general/2003-October/00
1090.htmlHi Zack,
It's my understanding that gensky produces sky type 1, which is the
standard overcast sky, and sky type 12 for the clear sky from the 15 in
the CIE table from 2003. I'm not sure which one it uses for the
intermediate sky, nor do I know if it's using the 5 parameter method or
something else.- Rob
_______________________________________________
Radiance-general mailing list
Radiance-general@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
Hi all,
just a note on the 15 "new" CIE sky types from 2003: these luminance
distributions can be
used in Radiance using Philipp Greenup's ssldlum.cal that can be downloaded
from
www.radiance-online.org/patches/ssld/SSLD algorithm with PDF.zip
However, afaik these models are not commonly used (and even not really well
known)...
A short note on Rob's comment: if I remember right the new CIE sky type 1
is slightly different
from the "good old" overcast sky. That's why the classical overcast sky
(with the 3:1 distribution
L(gamma)/L(zenith) = (1+2*sin(gamma))/3 ) is defined as additional 16th sky
type in the CIE Standard.
Best,
David