I need feedback or help to calculate daylight for LEED using Radiance.
Have anyone here acomplished this calculations before? I know that I have
to use footcandles for LEED and radiance use cd/m2. I have to convert each
grid point and the scale to footcandle?
Best regards
···
--
Jorge Ignacio Fajardo F-A
Arquitecto *MDCS*
iBSA - Ingeniería Blanda S.A
USGBC Member
Jean Mermoz 12, of. D
Of.: (562) 934.7083
Cel. (567) 8782497
You can indeed calculate the values you need for the LEED daylight credit documentation with Radiance. To be clear, Radiance by default calculates, well, radiance, in w/sr/m^2. This can be converted to luminance (cd/m^2). Now, to get the info you need for LEED, you need to tell Radiance to calculate irradiance instead of radiance, and convert that to lux or footcandles as needed. To do this you would specify the –I (capitol i) option to rtrace, which is the Radiance tool you'd use to calculate values for a grid of points, and then multiply the rgb irradiance values by V lambda. There are plenty of examples in the list archives of little scripts and commands to send Radiance a grid of points and do these calculations and make the proper conversions to the photometric values.
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
1617 Cole Blvd MS:RSF202
Golden, CO 80401
T. 303.275.4319
F. 303.630.2055
E. [email protected]
I need feedback or help to calculate daylight for LEED using Radiance.
Have anyone here acomplished this calculations before? I know that I have to use footcandles for LEED and radiance use cd/m2. I have to convert each grid point and the scale to footcandle?
Best regards
--
Jorge Ignacio Fajardo F-A
Arquitecto MDCS
iBSA - Ingeniería Blanda S.A
USGBC Member
Jean Mermoz 12, of. D
Of.: (562) 934.7083
Cel. (567) 8782497
Our DIVA tool provides calculations in both units (www.diva-for-rhino.com). You of course simply do the calculation in lux and then convert to foot-candles.
I need feedback or help to calculate daylight for LEED using Radiance.
Have anyone here acomplished this calculations before? I know that I have to use footcandles for LEED and radiance use cd/m2. I have to convert each grid point and the scale to footcandle?
Best regards
--
Jorge Ignacio Fajardo F-A
Arquitecto MDCS
iBSA - Ingeniería Blanda S.A
USGBC Member
Jean Mermoz 12, of. D
Of.: (562) 934.7083
Cel. (567) 8782497
Jorge,
This suggestion is not necessarily a help, and may even prove to be a hindrance, but if you're attempting the 'clear sky' option in either LEED or ASHRAE, you may wish to acquaint yourself with some of the er. peculiarities of the specification: http://www.iesd.dmu.ac.uk/~jm/doku.php?id=academic:daylight-compliance#various_guidelines
Whilst one imagines that there must be some rationale behind these ‘clear sky’ formulations, it has never been laid bare and I have to confess bewilderment as to what the reasoning might be.
Good luck!
John
···
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
You make a very good point, reviewing the LEED docs again it does not
clarify the "clear" sky model to use. I have always assumed it was the
IESNA recommended clear sky definition which does give consistent and
predictable horizontal illuminance. In my practice, I have found measured
clear skies to match up very well with these guidelines. I live in sunny
Boulder, true, but last fall we measured 32 mostly clear skies in South
Carolina which all matched up very well with the IESNA predicted horizontal
illuminance. The luminance distributions were not far off either.
From what I understand, IESNA Handbook 9 adopted the same clear, partly
cloudy, and cloudy luminance distributions created by Kittler and also
adopted by the CIE at the time (I believe CIE has now adopted a broader set
of 15 skies or so covering more intermediate conditions). In addition to
this, the IESNA handbook 9 offers a series of tables and equations for
calculating the Zenith Luminance allowing one to predict the magnitude of
these skies under different conditions. Does the CIE not have a similar
recommendation for calculating the zenith luminance? From what I
understand, the CIE sky models rely on input of either zenith luminance or
horizontal illuminance from weather data.
BTW - the latest public review draft of LEED 2012 goes away from this
standard clear sky and requires the user to find the average hourly values
between the clearest and cloudiest days within 15days of Sept 21 and Mar
21st. Someone must have been listening to your concerns!
Cheers,
Zack
PS. I have a python "IES_gensky.py" script and a "IES_skybright.cal" that
generates the IESNA sky definitions. I have been using this solely for
"design day" daylight illuminance calculations for the past 8 years in lieu
of gensky. It is used and available in the SPOT program. I'd be happy to
share with anyone, e-mail me directly and I will respond with it.
···
On Thu, Apr 14, 2011 at 2:53 PM, John Mardaljevic <[email protected]> wrote:
Jorge,
This suggestion is not necessarily a help, and may even prove to be a
hindrance, but if you're attempting the 'clear sky' option in either LEED or
ASHRAE, you may wish to acquaint yourself with some of the er. peculiarities
of the specification:
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or zenith luminance. Both options of course available in gensky. I'm not too familiar with the procedures used to estimate sky type and magnitude since I invariably use climate data as the basis for defining skies. For what it's worth, I've long believed that there was a 'disconnect' between what the sky model researchers were doing and what end-users might actually want, i.e. a means of selecting sky type from basic quantities in the standardised climate files.
Even if one could claim that a particular clear sky output was plausible, it still seems wacky to predict for a clear sky without sun. I've updated my commentary on this with a graphic to show just how much might be missing if you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this standard clear sky and requires the user to find the average hourly values between the clearest and cloudiest days within 15days of Sept 21 and Mar 21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a confounding notion, and often lead to contortions best left to people who enjoy doing this:
Do you have actual wording from the LEED draft?
Best
John
···
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or
zenith luminance. Both options of course available in gensky. I'm not too
familiar with the procedures used to estimate sky type and magnitude since I
invariably use climate data as the basis for defining skies. For what it's
worth, I've long believed that there was a 'disconnect' between what the sky
model researchers were doing and what end-users might actually want, i.e. a
means of selecting sky type from basic quantities in the standardised
climate files.
Even if one could claim that a particular clear sky output was plausible,
it still seems wacky to predict for a clear sky without sun. I've updated my
commentary on this with a graphic to show just how much might be missing if
you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this
standard clear sky and requires the user to find the average hourly values
between the clearest and cloudiest days within 15days of Sept 21 and Mar
21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a
confounding notion, and often lead to contortions best left to people who
enjoy doing this:
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
- The first is how to specify Radiance calculate irradiance
I was searching where to specify -I (the capitol i) to rtrace in Radiance
to calculate irradiance instead radiance and I found in Autodesk Ecotect
Calculation wizard - Radiance Analysis (step 10-11) the -I blank, but i dont
know what to do because is already wrote and have a blank beside. Others
command have diferents values. I´m in the right place to specify?
- My second doubt is in what place i need to "mutiply the rgb irrandiance
values by V lambda" I need to be in Analysis Grid Management - Edit Grid
Data in Ecotect ?
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or
zenith luminance. Both options of course available in gensky. I'm not too
familiar with the procedures used to estimate sky type and magnitude since I
invariably use climate data as the basis for defining skies. For what it's
worth, I've long believed that there was a 'disconnect' between what the sky
model researchers were doing and what end-users might actually want, i.e. a
means of selecting sky type from basic quantities in the standardised
climate files.
Even if one could claim that a particular clear sky output was plausible,
it still seems wacky to predict for a clear sky without sun. I've updated my
commentary on this with a graphic to show just how much might be missing if
you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this
standard clear sky and requires the user to find the average hourly values
between the clearest and cloudiest days within 15days of Sept 21 and Mar
21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a
confounding notion, and often lead to contortions best left to people who
enjoy doing this:
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
It is always a bit confusing when folks think they ask about Radiance, but actually have questions related to Ecotect's user interface. So without knowing Ecotect, I try to help a bit:
- The first is how to specify Radiance calculate irradiance
I was searching where to specify -I (the capitol i) to rtrace in
Radiance to calculate irradiance instead radiance and I found in
Autodesk Ecotect Calculation wizard - Radiance Analysis (step 10-11) the
-I blank, but i dont know what to do because is already wrote and have a
blank beside. Others command have diferents values. I´m in the right
place to specify?
Probably the blank is because "-I" is a switch to get irradiance instead of radiance as output. So you do not pass any value (and thus there also cannot be a default). Basically rtrace -I interpretes input coordinates/directions as sensor locations (coordinate) and sensor view directions (directions). So 0 0 0 0 0 1 would be location (0,0,0) pointing up (0,0,1).
- My second doubt is in what place i need to "mutiply the rgb
irrandiance values by V lambda" I need to be in Analysis Grid Management
- Edit Grid Data in Ecotect ?
No idea, usually you need to weigh the RGB (unless you do everything with grey values) and multiply with the luminous efficacy in Radiance to get from radiometric to photometric units, but I have no clue where this is hidden in Ecotect.
As Lars pointed out, your questions at this point are more about how to get Ecotect to tell Radiance what you want to do. Hopefully some Ecotect users on the list can chime in about this…
Hi Rob
I feel a litle lost here .... have two doubt :
- The first is how to specify Radiance calculate irradiance
I was searching where to specify -I (the capitol i) to rtrace in Radiance to calculate irradiance instead radiance and I found in Autodesk Ecotect Calculation wizard - Radiance Analysis (step 10-11) the -I blank, but i dont know what to do because is already wrote and have a blank beside. Others command have diferents values. I´m in the right place to specify?
- My second doubt is in what place i need to "mutiply the rgb irrandiance values by V lambda" I need to be in Analysis Grid Management - Edit Grid Data in Ecotect ?
Rob I´m really thankful for your help.
Best regards
2011/4/15 Ignacio Fajardo <[email protected]<mailto:[email protected]>>
Thanks for your help! I´m gonna be honest, I need to study your answers.
Once I get there, I will certainly write you again!
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or zenith luminance. Both options of course available in gensky. I'm not too familiar with the procedures used to estimate sky type and magnitude since I invariably use climate data as the basis for defining skies. For what it's worth, I've long believed that there was a 'disconnect' between what the sky model researchers were doing and what end-users might actually want, i.e. a means of selecting sky type from basic quantities in the standardised climate files.
Even if one could claim that a particular clear sky output was plausible, it still seems wacky to predict for a clear sky without sun. I've updated my commentary on this with a graphic to show just how much might be missing if you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this standard clear sky and requires the user to find the average hourly values between the clearest and cloudiest days within 15days of Sept 21 and Mar 21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a confounding notion, and often lead to contortions best left to people who enjoy doing this:
Do you have actual wording from the LEED draft?
Best
John
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
Rob I visit your website and I like a lot your radiance renders!! just
perfect, I render with other programs and maxell is closer to radiance, but
radiance gives you data... more usefull.
About my LEED doubts I answer myself, because Ecotect give the options to
calculate Radiance (luminace) cd/m2 or Irradiance (illuminance) lx/m2, so,
I´m sure that we are ok with that because you choose cd/m2 option.
Now, to convert cd/m2 to cd/ft2 for LEED I need to convert each node
values - V*0.092903 (V is the node value, and 0.09... is the value to
transform 1cd/m2 to cd/ft) in Ecotect you can do that in grid management.
I hope this informations can be usefull ... anyway, comments are welcome to
be sure what I´m doing.
As Lars pointed out, your questions at this point are more about how to get
Ecotect to tell Radiance what you want to do. Hopefully some Ecotect users
on the list can chime in about this…
Hi Rob
I feel a litle lost here .... have two doubt :
- The first is how to specify Radiance calculate irradiance
I was searching where to specify -I (the capitol i) to rtrace in Radiance
to calculate irradiance instead radiance and I found in Autodesk Ecotect
Calculation wizard - Radiance Analysis (step 10-11) the -I blank, but i dont
know what to do because is already wrote and have a blank beside. Others
command have diferents values. I´m in the right place to specify?
- My second doubt is in what place i need to "mutiply the rgb irrandiance
values by V lambda" I need to be in Analysis Grid Management - Edit Grid
Data in Ecotect ?
Rob I´m really thankful for your help.
Best regards
2011/4/15 Ignacio Fajardo <[email protected]<mailto:[email protected]>>
Thanks for your help! I´m gonna be honest, I need to study your answers.
Once I get there, I will certainly write you again!
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or
zenith luminance. Both options of course available in gensky. I'm not too
familiar with the procedures used to estimate sky type and magnitude since I
invariably use climate data as the basis for defining skies. For what it's
worth, I've long believed that there was a 'disconnect' between what the sky
model researchers were doing and what end-users might actually want, i.e. a
means of selecting sky type from basic quantities in the standardised
climate files.
Even if one could claim that a particular clear sky output was plausible,
it still seems wacky to predict for a clear sky without sun. I've updated my
commentary on this with a graphic to show just how much might be missing if
you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this
standard clear sky and requires the user to find the average hourly values
between the clearest and cloudiest days within 15days of Sept 21 and Mar
21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a
confounding notion, and often lead to contortions best left to people who
enjoy doing this:
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
What website did you visit? Because I can point you to a bunch of other websites with far nicer Radiance renderings than mine! =) I agree though, Radiance is nice because it gives you useful data, not just "pretty pictures".
OK, your second paragraph below is quite the unit salad. Let's sort this out as best I can, not having Ecotect to look at. You say "Ecotect give the options to calculate Radiance (luminace) cd/m2 or Irradiance (illuminance) lx/m2". You're mixing and matching quantities here. For LEED daylighting calcs, you ultimately need illuminance. This is lumens/m^2, NOT lux/m^2. 1 Lux = 1lm/m^2. So, just make sure you are asking for illuminance. Not irradiance, not luminance, but illuminance -- which should be in lux, or lumens/m^2. Next, you mention this node value conversion. I assume a node value is a calculation grid point. Your conversion value is correct to convert from metric units to imperial units. So, assuming you are indeed calculating illuminance, in lux (lumens/m^2), then multiplying those values by 0.0929030436 will convert the values to footcandles (lumens/m^2).
Hope this helps, I'm not really sure about any of the GUI specific questions you have because I don't use or have Ecotect.
Rob Guglielmetti IESNA, LEED AP
Commercial Buildings Research Group
National Renewable Energy Laboratory
1617 Cole Blvd MS:RSF202
Golden, CO 80401
T. 303.275.4319
F. 303.630.2055
E. [email protected]<mailto:[email protected]>
Rob I visit your website and I like a lot your radiance renders!! just perfect, I render with other programs and maxell is closer to radiance, but radiance gives you data... more usefull.
About my LEED doubts I answer myself, because Ecotect give the options to calculate Radiance (luminace) cd/m2 or Irradiance (illuminance) lx/m2, so, I´m sure that we are ok with that because you choose cd/m2 option.
Now, to convert cd/m2 to cd/ft2 for LEED I need to convert each node values - V*0.092903 (V is the node value, and 0.09... is the value to transform 1cd/m2 to cd/ft) in Ecotect you can do that in grid management.
I hope this informations can be usefull ... anyway, comments are welcome to be sure what I´m doing.
As Lars pointed out, your questions at this point are more about how to get Ecotect to tell Radiance what you want to do. Hopefully some Ecotect users on the list can chime in about this…
Hi Rob
I feel a litle lost here .... have two doubt :
- The first is how to specify Radiance calculate irradiance
I was searching where to specify -I (the capitol i) to rtrace in Radiance to calculate irradiance instead radiance and I found in Autodesk Ecotect Calculation wizard - Radiance Analysis (step 10-11) the -I blank, but i dont know what to do because is already wrote and have a blank beside. Others command have diferents values. I´m in the right place to specify?
- My second doubt is in what place i need to "mutiply the rgb irrandiance values by V lambda" I need to be in Analysis Grid Management - Edit Grid Data in Ecotect ?
Rob I´m really thankful for your help.
Best regards
2011/4/15 Ignacio Fajardo <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>>
Thanks for your help! I´m gonna be honest, I need to study your answers.
Once I get there, I will certainly write you again!
Indeed, the CIE skies can be defined by diffuse horizontal illuminance or zenith luminance. Both options of course available in gensky. I'm not too familiar with the procedures used to estimate sky type and magnitude since I invariably use climate data as the basis for defining skies. For what it's worth, I've long believed that there was a 'disconnect' between what the sky model researchers were doing and what end-users might actually want, i.e. a means of selecting sky type from basic quantities in the standardised climate files.
Even if one could claim that a particular clear sky output was plausible, it still seems wacky to predict for a clear sky without sun. I've updated my commentary on this with a graphic to show just how much might be missing if you don't include the sun:
BTW - the latest public review draft of LEED 2012 goes away from this standard clear sky and requires the user to find the average hourly values between the clearest and cloudiest days within 15days of Sept 21 and Mar 21st. Someone must have been listening to your concerns!
Perhaps, half-listening. Averages for daylighting quantities can be a confounding notion, and often lead to contortions best left to people who enjoy doing this:
Do you have actual wording from the LEED draft?
Best
John
-----------------------------------------------
Dr. John Mardaljevic
Reader in Daylight Modelling
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
On Apr 22, 2011, at 0:37, "Guglielmetti, Robert" <[email protected]> wrote:
So, assuming you are indeed calculating illuminance, in lux (lumens/m^2), then multiplying those values by 0.0929030436 will convert the values to footcandles (lumens/m^2).
Actually lm/ft2. You see what a mess the mixing of metric and imperial system leads to if these typos appear even in Rob's explanation.
If it was my office, the first thing I'd do is to establish a policy to only use metric units everywhere (geometry, results,...). The conversion to imperial units can be done on the fly when filling out a form.
By the way, it is rather important to understand the difference between Radiance W/m2sr and Irradiance W/m2. Going from radiometric (W aka Watts) to photometric (lm aka lumens) is just to match the human eye's perception according to wavelengths, and in many cases Radiance can internally do this on your behalf.
On Apr 21, 2011, at 11:54 PM, "Lars O. Grobe" <[email protected]> wrote:
Hi!
On Apr 22, 2011, at 0:37, "Guglielmetti, Robert" <[email protected]> wrote:
So, assuming you are indeed calculating illuminance, in lux (lumens/m^2), then multiplying those values by 0.0929030436 will convert the values to footcandles (lumens/m^2).
Actually lm/ft2. You see what a mess the mixing of metric and imperial system leads to if these typos appear even in Rob's explanation.
If it was my office, the first thing I'd do is to establish a policy to only use metric units everywhere (geometry, results,...). The conversion to imperial units can be done on the fly when filling out a form.
By the way, it is rather important to understand the difference between Radiance W/m2sr and Irradiance W/m2. Going from radiometric (W aka Watts) to photometric (lm aka lumens) is just to match the human eye's perception according to wavelengths, and in many cases Radiance can internally do this on your behalf.
Searching on internet I realize that I´m very lucky to be in the same mail
list with both of you. Let me show me respect and gratitude.
I still have a question in units to use for LEED calculations and I write
below some important data to remember:
* Robert told us to use for LEED :*
Illuminance lm/m2 (lumens/m2)*
···
*
*Radiance web site :*
Radiance / Luminance (W/sr.m2, cd/m2)
Irradiance / Iluminance (W/m,lux)
*Ecotect options:*
Luminance Image (cd/m2)
Iluminance Image (lux/m2) may be, must mean lm/m2
* LEED requeriements :*
25 footcandle min
500 footcandle max
So, Rob and Lars I´m going to use *Iluminance image* Options on Ecotect to
have result in lux (lumens/m^2), then multiplying those values by
0.0929030436 will convert the grid values to footcandles (1lm/m2 = 0.09
foot-candle) http://www.convertworld.com/en/illuminance/
LEED mentions that 75% of the zone must be between 25 and 500 footcandle, So
If I do the conversion (Lumens/m2) x (0.09) that value in the grid point
can be use to complete the % of area for LEED.
Lars you correct Rob about a mistake in theunits…
ROB: *“So, assuming you are indeed calculating illuminance, in lux
(lumens/m^2), then multiplying those values by 0.0929030436 will convert the
values to footcandles (lumens/m^2).”*
LARS: *Actually lm/ft2. You see what a mess the mixing of metric and
imperial system leads to if these typos appear even in Rob's explanation.***
… But the units still footcandles right? The confusion was that Rob meant
lumens/ ft2.
Guys…please confirm the information above is correct and have a look to the
website if you have time.
There are a whole bunch of people on this list that I'm thankful for knowing; it's truly a great bunch, and I have learned a lot from these people, both on- and off-list. To answer your question, yes, it sounds like the "illumimance image" option is what you want, since it gives you a result in SI illuminance units (lux) -- which you can convert to footcandles with that multiplier so that the LEED reviewers are happy. Sorry for adding confusion by botching the units in my previous post. For the record: one footcandle is equal to one lumen in a square foot!
Searching on internet I realize that I´m very lucky to be in the same mail list with both of you. Let me show me respect and gratitude.
I still have a question in units to use for LEED calculations and I write below some important data to remember:
Robert told us to use for LEED :
Illuminance lm/m2 (lumens/m2)
Radiance web site :
Radiance / Luminance (W/sr.m2, cd/m2)
Irradiance / Iluminance (W/m,lux)
Ecotect options:
Luminance Image (cd/m2)
Iluminance Image (lux/m2) may be, must mean lm/m2
LEED requeriements :
25 footcandle min
500 footcandle max
So, Rob and Lars I´m going to use Iluminance image Options on Ecotect to have result in lux (lumens/m^2), then multiplying those values by 0.0929030436 will convert the grid values to footcandles (1lm/m2 = 0.09 foot-candle) http://www.convertworld.com/en/illuminance/
LEED mentions that 75% of the zone must be between 25 and 500 footcandle, So If I do the conversion (Lumens/m2) x (0.09) that value in the grid point can be use to complete the % of area for LEED.
Lars you correct Rob about a mistake in theunits…
ROB: “So, assuming you are indeed calculating illuminance, in lux (lumens/m^2), then multiplying those values by 0.0929030436 will convert the values to footcandles (lumens/m^2).”
LARS: Actually lm/ft2. You see what a mess the mixing of metric and imperial system leads to if these typos appear even in Rob's explanation.
… But the units still footcandles right? The confusion was that Rob meant lumens/ ft2.
Guys…please confirm the information above is correct and have a look to the website if you have time.
