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asked 2016-04-13 11:37:29 -0600

luis melo gravatar image

updated 2016-04-17 10:02:01 -0600

Wich is the most suitable tool for monthly energy consumption assessment, in terms of daylighting benefits?

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answered 2016-04-17 10:01:25 -0600

Are you truly interested in only these two applications? I ask because both of these tools are somewhat dated, and development based on these two has shifted to other tools, and other tools exist as well. The short answer to this question is "neither, you should use DAYSIM 4.0", but there is more to this story (see below).


Currently, the DAYSIMps developers (basically (The) Penn(sylvania) State University) are working on a tool called STADIC, which is their evolution of DAYSIMps. The project was to overhaul the daylighting calculations to use Radiance proper and leverage the 5-phase method, and then build on the electric lighting controls piece. Currently it's still focused on the daylighting calculations bit. The code is located here.

The developers behind DAYSIM have DIVA for Rhino, which is a very robust application for doing climate based daylight modeling (CBDM) and relating it to electric lighting energy savings.

But then there is also the Sensor Placement + Optimization Tool (aka SPOT). I would argue that SPOT is the tool that has been most focused on (as its name implies) the lighting controls piece, as they relate to daylighting. SPOT can export lighting schedules for you to place in energy models (EnergyPlus/eQuest).

There is also a Radiance script or "measure" in current versions of OpenStudio, which will automatically do a Radiance daylighting simulation of your entire building, and modify the electric lighting schedules accordingly, even passing these to the EnergyPlus whole building simulation, thus automatically giving you what you have requested in your original question: monthly lighting energy consumption. You can even use OpenStudio's PAT application to set up a parametric analysis comparing your design (or generating an array of designs, even) both with and without the daylighting controls.

My point is that there are a lot of options out there, and this isn't even all of them. You need to consider what it is you're trying to get out of these simulations, the level of detail required, and how much time you have.

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Thank you Rob!! I already ran your last alternative, and the results were more accurate than in energyplus. About 5 times lower because the splitflux method used in Eplus overestimated the illuminance values, I guess!!

Thank so much for help

luis melo gravatar image luis melo  ( 2016-04-17 13:30:14 -0600 )edit

5x lower, huh? Well it could be an overestimation in the EnergyPlus calculation, but it could also be an underestimation by Radiance. Or they could each be off by 2.5x, in different directions. ¯_(ツ)_/¯ Seriously, you need to think about sensor placement, illuminance map size, Radiance settings, zone size and shape, etc. All of these things can affect the results.

rpg777 gravatar image rpg777  ( 2016-04-17 16:45:40 -0600 )edit

Technically, they would each have to be off by a factor of sqrt(5), which is closer to 2.2x than 2.5x. Sorry. Had to.

__AmirRoth__ gravatar image __AmirRoth__  ( 2016-04-17 20:25:39 -0600 )edit

Ok Rob, I'll check this parameters, for instance, the illumminance map is closer than 0,30 m from walls and probably it can affect the result. Thank you!

luis melo gravatar image luis melo  ( 2016-04-18 03:50:21 -0600 )edit

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Asked: 2016-04-13 11:37:29 -0600

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Last updated: Apr 17 '16