Glare and visual confort indices -- Are they ready?

Dear List,

Even if this is not a question regarding the use of Radiance, it certainly
is something related to this list or at least the expertise of its
participants. I want to start a discussion.

As a small group of you may know, I am the developer of a Radiance-based
lighting tool. This tool has the purpose of taking the state-of-the-art
daylighting calculation methods and practices to industry. However, since
industry sometimes just jump over a software, I am always worried about
methods and tool being used incorrectly.

In this last regard, I have been wondering for a while whether I should add
glare calculation capabilities or not. My impression is that they are
incredibly easy to misuse. For example, at the NREL's 12th Radiance
Workshop, Jan Wienold and Kevin Van Den Wymelenberg made Glare-oriented
presentations that did not really agree much.

So, my question is: are glare indices, such as UGR, DGP, etc. etc. ready
for use? Maybe only the Electric Lighting ones are ready? How about the
Daylighting ones? I do not want to offer something that looks like a magic
black-box, but which leads to incorrect results. I also know that having
something is better than nothing, but that only works as long as that
"something" helps guiding the design in the right direction.

Thanks very much in advance.

Germán

I’m not well-versed enough to give an opinion on which are ready for use in any particular application, but I would give *my* opinion on your closing thoughts. If the calculation method for the metric isn’t changing, but maybe there’s ongoing research into appropriate values and applications, maybe the metric is useful enough to help “guide the design in the right direction.” However there may be some metrics that have gone out of favor or been invalidated by current research that could be excluded – to avoid a curious user applying something they shouldn’t. But sometimes even the outdated metrics may still be referenced in some governing design standard and a user may need it for a particular project.

As with any other metric, the designer has to know the correct application and the appropriate target values, or which magnitude of difference between two designs might be considered negligible. Something as simple as illuminance isn’t changing in principle, but the design standards and recommended values are still changing and being clarified or fine-tuned. And a designer has to know the appropriate application where daylight factor, or daylight autonomy is an appropriate metric. So if a particular metric is in question and has ongoing research into application limits, tolerance thresholds, etc., a designer may not have full confidence to say a value of X.X in a particular metric is “good enough,” but if they have two design options they can hopefully make a reasonable judgment on which is better (as long as the metric hasn’t been invalidated!).

-Chris

···

From: Germán Molina Larrain [mailto:[email protected]]
Sent: Friday, December 02, 2016 7:27 AM
To: Radiance general discussion
Subject: [Radiance-general] Glare and visual confort indices -- Are they ready?

Dear List,

Even if this is not a question regarding the use of Radiance, it certainly is something related to this list or at least the expertise of its participants. I want to start a discussion.

As a small group of you may know, I am the developer of a Radiance-based lighting tool. This tool has the purpose of taking the state-of-the-art daylighting calculation methods and practices to industry. However, since industry sometimes just jump over a software, I am always worried about methods and tool being used incorrectly.

In this last regard, I have been wondering for a while whether I should add glare calculation capabilities or not. My impression is that they are incredibly easy to misuse. For example, at the NREL's 12th Radiance Workshop, Jan Wienold and Kevin Van Den Wymelenberg made Glare-oriented presentations that did not really agree much.

So, my question is: are glare indices, such as UGR, DGP, etc. etc. ready for use? Maybe only the Electric Lighting ones are ready? How about the Daylighting ones? I do not want to offer something that looks like a magic black-box, but which leads to incorrect results. I also know that having something is better than nothing, but that only works as long as that "something" helps guiding the design in the right direction.
Thanks very much in advance.
Germán

Thanks, Chris! I believe this question is meant to be answer based on
opinions.

I agree that people need to know what they are doing... metrics ALWAYS
should be carefuly chosen, even if they have been validated (that is why I
have intentions of writing a good documentation). That being said, I am not
quite sure (just because of my own ignorance) if Evalglare and DGP, for
example, are ready for design use. I mean, *Will it produce useful
information in all or most or enough design cases, provided that all the
parameters are set correctly? Or is it limited to certain positions and
room configurations? How about the other metrics?* I personally usually
design using illuminance-based metrics and am not quite sure when would I
use luminance-based ones.

I am very new at glare, but I have heard people I respect say that we still
do not know much about it, thus my question. Is it worth including such
features in Groundhog? I want to keep this tool at the state-of-the-art,
but only if state-of-the-art methods are ready for use.

Kind regards,

Germán

···

2016-12-02 11:10 GMT-03:00 Christopher Rush <[email protected]>:

I’m not well-versed enough to give an opinion on which are ready for use
in any particular application, but I would give *my* opinion on your
closing thoughts. If the calculation method for the metric isn’t changing,
but maybe there’s ongoing research into appropriate values and
applications, maybe the metric is useful enough to help “guide the design
in the right direction.” However there may be some metrics that have gone
out of favor or been invalidated by current research that could be excluded
– to avoid a curious user applying something they shouldn’t. But sometimes
even the outdated metrics may still be referenced in some governing design
standard and a user may need it for a particular project.

As with any other metric, the designer has to know the correct application
and the appropriate target values, or which magnitude of difference between
two designs might be considered negligible. Something as simple as
illuminance isn’t changing in principle, but the design standards and
recommended values are still changing and being clarified or fine-tuned.
And a designer has to know the appropriate application where daylight
factor, or daylight autonomy is an appropriate metric. So if a particular
metric is in question and has ongoing research into application limits,
tolerance thresholds, etc., a designer may not have full confidence to say
a value of X.X in a particular metric is “good enough,” but if they have
two design options they can hopefully make a reasonable judgment on which
is better (as long as the metric hasn’t been invalidated!).

-Chris

*From:* Germán Molina Larrain [mailto:[email protected]]
*Sent:* Friday, December 02, 2016 7:27 AM
*To:* Radiance general discussion
*Subject:* [Radiance-general] Glare and visual confort indices -- Are
they ready?

Dear List,

Even if this is not a question regarding the use of Radiance, it certainly
is something related to this list or at least the expertise of its
participants. I want to start a discussion.

As a small group of you may know, I am the developer of a Radiance-based
lighting tool. This tool has the purpose of taking the state-of-the-art
daylighting calculation methods and practices to industry. However, since
industry sometimes just jump over a software, I am always worried about
methods and tool being used incorrectly.

In this last regard, I have been wondering for a while whether I should
add glare calculation capabilities or not. My impression is that they are
incredibly easy to misuse. For example, at the NREL's 12th Radiance
Workshop, Jan Wienold and Kevin Van Den Wymelenberg made Glare-oriented
presentations that did not really agree much.

So, my question is: are glare indices, such as UGR, DGP, etc. etc. ready
for use? Maybe only the Electric Lighting ones are ready? How about the
Daylighting ones? I do not want to offer something that looks like a magic
black-box, but which leads to incorrect results. I also know that having
something is better than nothing, but that only works as long as that
"something" helps guiding the design in the right direction.

Thanks very much in advance.

Germán

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