Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page
Ask Your Question

daylight glare simulation in terms of DGPs

asked 2018-11-02 04:24:42 -0500

Yi.Z gravatar image

updated 2018-11-26 20:04:29 -0500

Hi everyone! I decide to use OpenStudio to simulate the impact of opposite buildings reflection on daylight glare conditions of open office. I know that the OpenStudio can only do daylight glare simulation with DGPs index but the simplified DGP(DGPs) ignores the size of glare source and other parameters related to glare source. I wonder is the DGPs applicable to my cases when the reflection of opposite buildings can't be ignored. Or is there any other index that you recommend for my case? I've considered the DGP but the simulation in Radiance is really time consuming cause I have to run a yearly simulation to reflect the temporal influence.

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted

answered 2018-11-02 09:32:31 -0500

Yes, the expression "there's no such thing as a free lunch" applies here. Simplified DGP takes eye illuminance as the input, which is a simple integral of the incoming flux across the hemisphere and therefore lacks the information to do a proper DGP as you state. It's a fast enough thing to compute that doing so over an annual basis is actually tractable, which is why we put it in the OpenStudio Radiance measure. But it's kinda only valid in cases where there isn't a lot of unruly stuff like direct solar views (or reflections) going on. There may be cases where DGPs overstates the problem because high-angle flux that may be in a non-problematic position index will smear its way into the illuminance input value. Conversely, there could be a tiny reflection of direct sun directly in the everyday field of view that's being minimized, due to the same smearing.

I'm a firm believer in the value of UDI for doing a rough first pass of glare analysis on an annual basis, but for serious detail work or for difficult cases (which it sounds like you have there), I recommend augmenting those studies with high-quality point-in-time images-based glare analysis using the full DGP. Also look at Ladybug Tools, I believe they offer the "enhanced DGPs" option, which is also a nice middle ground.

Friday Bonus Links!

edit flag offensive delete link more


Thanks a lot for your advice! I decide to use UDI to do a rough first pass on an annual basis to find out some comparatively worse situation and then do accurate simulation of DGP, using RADIANCE, on those comparatively worse hours. Hope that the discrepancy between the annual UDI change trend and DGP would be small.

Yi.Z gravatar image Yi.Z  ( 2018-11-11 21:23:14 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer


Question Tools



Asked: 2018-11-02 04:24:42 -0500

Seen: 248 times

Last updated: Nov 02 '18