daylighting results do not change during the day, thought the year

[cabalakornelia]

Hello, I'm writing to You, because I have a problem with my daylighting results. When I'm clicking the earth icon and changing from for example spring equinox to winter solstice and then calculating again daylighting analysis the results do not changing, the same situation is when I'm changing hour of the day. I'm checking it for desk height 700. The another thing is that when I put three points on the first grid and then calculating daylighting at specific points in the model for selected points only and comparing the value from selection information from attribute1 (56.6466) and the nearest value on the grid (15.99) the difference of the values for daylight factor is huge. I would be grateful if you help me solve that problems. I'm enclosing the file.

[Pennetier1]

Hello cabalakornelia, 

The Daylight factor analysis is independent of the time of day, year or even location; it is only dependent on your design configuration, such as the size of your windows or the reflectivity of your material.  This enable designers to compare designs independent of their location. 

The reason it is not dependent on the time of day or year is because it uses an overcast sky model; since the sky is assumed to be overcast (worst case scenario), then there is no sun.  So time of day, year or even location is irrelevant.

If you want to get actual illuminance values for particular times of day, year, or location, you have to export your model/grid to Radiance.

Your point's value is indeed way too high compared to that of the grid's node.  Something is off as it should be pretty close, if not quite perfectly the same. 

I am assuming you got all this correct, but let's go through a quick checklist:

* Make sure the point object is located at the same height as the grid. It almost looks like you point object is somehow on the exterior of your zone or very close to the ceiling or floor given its value.

* Again, make sure you are using exactly the same analysis setting for both the point object and the analysis grid.

* Double check that your object attribute is indeed the same units as the analysis grid (Daylight factor) - it could be set to another unit but I doubt it.

If you cannot figure this out, go ahead and send me your .eco file - I might be able to have a quick look for anything obvious.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[cabalakornelia]

Now the problem is that i followed all the instructions from the link http://www.youtube.com/watch?v=VSw-DYrgS68 and there were used three additional links: http://openstudio.nrel.gov/getting-started-developer/getting-started-radiance and http://pyrat.googlecode.com/files/falsecolor2.exe and http://www.ise.fraunhofer.de/en/downloads-englisch/software/evalglare_windows.zip/view, and when i tried to run a simulation with radiance i got the following error: It said: missing vital files:"falsecolor.exe" and "rview.exe". I had two files falsecolor2.exe and rvu.exe so I changed their names for required and started to render, but unfortunately no image had appeared. 

My points's value are fine now 🙂 You were right the height was different than the height of the grid.

[cabalakornelia]

I also installed Desktop Radiance 2.0 Beta, although it was't able to find the dayfact.exe file ( after that I didn't find it on the net I ignored that fact and completed the installation without it) and there still is no image in image viewer.

[Pennetier1]

Hi cabalakornelia, 

The only 2 plug-ins to Ecotect for Light analysis are Desktop Radiance and DAYSIM.

I am attaching two documents here to guide you on the Desktop Radiance installation and how to get you started with the analyses with both Radiance and DAYSIM.

Dayfact.exe is not part of the Desktop Radiance program; however, you will still have the option to calculate the daylight factor using Desktop Radiance. See more info on that here.

You also have access to the Ecotect Wiki pages for Radiance analysis tutorials here.

I hope that helps.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[Mohammad_Asl]

Hi,

This might be not directly related to your question but I wanted to make sure that you know about our new options for lighting and daylighting analysis in Revit. Here is some more information on this:

• Illuminance Rendering in Revit (Rendering as Service) - Learn about Illuminance renderings which are used to help understand if the space is adequately light for its intended use. Learn how to use the tool from BPA Help.

• Lighting Analysis for Revit - Lighting Analysis for Revit is a fast cloud service that uses Autodesk 360 Rendering to expose electric and solar lighting results directly on the Revit model. The results are validated against Radiance, a commonly used simulation tool, and displayed in-canvas more quickly. The service also offers automated daylighting analysis for LEED. Learn how to use the tool from BPA Help about Lighting Analysis for Revit.

Please try these applications if relevant and ask your questions on Lighting and Daylighting Analysis page on BPA Froum.

[Pennetier1]

Hi cabalakornelia

Here are the Radiance Intall attachment...

Here is a link to the Radiance/DAYSIM tutorial.

Cheers,

[cabalakornelia]

Hi, 

Firstly I would like to thank You for Your help 😄 The Radiance is running well right now, so it is a huge relief 🙂 Now I'm wondering on what norms, standards are you basing in case of lighting analysis done by Ecotect if there is no sun and if is not dependent on the time of the day, year? is it an average of results though the whole year or is it an average of two extreme values or like in Leed it is 21 September on 9 and 3 p.m.?

[Pennetier1]

Hi cabalakornelia, 

I am glad radiance is working out for you.

The internal daylight analysis engine in Ecotect uses the Daylight Factor method which is a standard in itself and is used in some building codes throughout the world, even though it may not be the most accurate methodology; it is fast and relatively simple enough to allow designers to estimate (sometimes by hands) the amount of daylight the space will receive on a worst case scenario, i.e. a typical winter day with no sun.

Here is an exerpt from the Ecotect Help files on the Daylight Factor:

It is a good metric to compare daylighting designs regardless of their locations or time of the day and year (as some locations have obviously brighter skies than others).

Ecotect offer the user this DF analysis to check for compliance with local codes (especially in the UK), but also allows the user to perform more accurate studies by integrating the Desktop Radiance interface, which will estimate the actual illuminance or luminance within a space for specific time of day and year, and accounting more multiple reflectances based on the materials reflectivities.

I hope that clarifies things a bit.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,