Solar Light Pipe simulation for option 1 method in LEED v4

It depends on the program that you are using for the simulations.  Some programs and the method that i have used before was to simulate the light tubes as electric lights. Solar tube used to have an IES file that you could use in your simulation.  Not sure how some programs would handle the simulation of the light tubes. If they are long, the simulation might not even document any illumination from them. Since the parameters for simulation are 5 bounces, it might not be enough for the light tube based on its length.  Measurement may be a viable option if the project is built. 

Hi,

I am looking at the possibility of inserting solatubes in my revit model and running the daylighting simulations using the Insight plugin. I can run the simulations by making the software factor in electrical lighting. I will delete all electric lights except solatubes so that it counts only that in the analysis. Has anyone tried that before. Does it work? 

Kavita

I have not done in it in Revit with Insight, but i have done it in other programs.  I believe Solar Tube has an IES file you can download that will represent the performance, but its been awhile since i have done this and things may have changed. 

I am working through this challenge right now using IES.  IES can account for the solar tubes as a fixture in option 2 calculations but not for SDA which is challenging. I think they may end up having to be modeled as geometry and then hoping with high reflectance for the tube that some daylight comes in to help SDA scoring.   Would be great if anyone has any other recommendations?

I have not gotten results from light tubes that are close to their actual performance when modeling it as a tube with high reluctance. You can only have up to five bounces (double IES LM 83 for specific modeling parameters) and that has them performing well below what they actually do.

Have you thought about another program. I know Light Stanza can do solar tubes for sDA.

Tubular daylighting devices are extremely complicated to physically model, as they use multi-bounce specular reflections to pipe light down the tube.  The normal ray-tracing algorithms used by Insight Lighting and Radiance and most others can't handle this (needs hundreds of bounces and forward-ray-tracing), and the tools made to model this condition take a very, very long time to simulate the effects.  It's a similar difficulty with other complex glazing like light-redirecting glass, etc.

The way some tools handle it is to use some sort of Specular Distribution definition for the interior panel of the device.  Radiance takes BSDF files for complex glazing and light sources, and Insight Lighting uses IES distribution files.  BSDF files are nice in that they calculate the interior distribution in relation to the exterior incident light, but I haven't found a tubular device maker that can provide these.

To model tubular daylighting devices like SolaTube in Insight Lighting, create a lighting fixture and apply the IES light distribution profile definition file appropriate for your location and time-date.  I've worked with SolaTube on projects like that, and they can provide a set of IES files for any location or time by defining the solar angle of incidence to the skylight.  There's some good info on the Insight Forum (search for 'SolaTube'), and I can send you more extensive instructions and IES files if you like.

Running a full annual sDA analysis using IES files is going to be a bit difficult though, as the IES file is specific for the incident solar angle for each hour.  You can do it easily for the equinox versions of the analysis types, but for full annual, you'd have to do some work with Dynamo using the Daylighting nodes, or move to Rhino-Grasshopper using Radiance and BSDF files.

BTW, I'm a developer of the Insight Lighting Revit addin, so feel free to post any further questions through the Autodesk Insight Lighting & Solar Analysis Forum, as we watch that regularly.

BSDF files are strongly preferable for the reasons you described David over IES files for modeling Tubular Daylight Devices and now available by manufacturers like Sunoptics, Solatube, and possibly Velux. 

LightStanza implemented this using Radiance, and from a user perspective, all you have to do is place the diffuser of the TDD where it is in the model and LS will take the sky and map it through the tube (via the manufacturer BSDF-- Sunoptics LightFlex system is currently in our library, but you can upload other manufacturers) and produce illuminances for renderings, animations, point calcs, LEED scores, etc.