# LEED v4 - Credit 7: Daylight, Option 2 (Point in time)

Dear DIVA team

In LEEDv4 EQc7 Option 2 we have to do a point in time evaluation of the illuminance level at 9 am and 15pm. The LEED guide writes:

4) From the TMY, select a day within 15 days of march 21 that has the clearest sky condition at 9am

5) Determine the direct horizontal irradiance (Wh/m2) values at 9am selected in September and at 9am for the day selected in march. Average the two values and use the result in the 9am simulation as the direct horizontal irradiance input. If the file does not explicitly state direct horizontal irradiance, calculate it as follows:

Direct horizontal irradiance = Global horizontal irradiance - Diffuse horizontal irradiance.

Has DIVA any built in function of finding the clearest sky condition within a range of days?

Best regards Mathias

Tags: EQc7, LEED, LEEDv4, Option2

Views: 1445

### Replies to This Discussion

Hi Mathias,

That is fascinating -- I hadn't read through the option 2 component of LEED v4. Unfortunately, this would have to be a manual exercise in DIVA. May I ask why you don't use Option 1. Simulation: Spatial Daylight Autonomy? It is included in the DIVA 3 Alpha under Climate-Based Metrics.

Alstan

Dear Alstan

Thanks for the reply.

We've done the option 1 and the results so far are too bright (working on a Saudi project). But we love the addition of the function - saved us a lot of postprocessing work with huge result files, thanks! But as we are a larger office, we are trying to optimise processes around LEED certification in general, including both options.

Mathias

Just a follow up:

Using ladybug and grasshopper we've made the following GH definition to find an average of the irradiance values from the clearest days +/-15 days of equinox.

However, this custom sky is made based on direct normal irradiance and diffuse horizontal irradiance, whereas the LEEDv4 book suggests a sky made from direct horizontal irradiance and diffuse horizontal irradiance. I suppose it ends up in the same sky, but I am awaiting confirmation from LEED. (see thread from Jody: http://www.leeduser.com/credit/NC-v4/EQc7#comment-53203 )

Hope this helps anyone else looking for their parameters :-)

Best, Mathias

Attachments:

Hi Matthias,

I see they also changed the lighting thresholds from 10-500fc to 300-3000 lx in the new iteration. We'll have to at least add in a new loading method to make the old LEED 8.1 display possible with option 2.

As for seeding a sky model with direct normal rather than direct horizontal, there should really be no difference in the resulting sky model (just a cosine correction). If I were a LEED reviewer, I would definitely allow it.

Best,

Alstan

Hi Alstan

Yes, this is true.

One has to make two simulations: one at 9am and one at 3pm, on equinox date (either september 21st or march 21st) using the averaged sky as described before. The simulations must be made with the two custom perez skies based on the average values for 9am and 3pm.

75% of the area must then be between 300 and 3000 lux (to obtain 1 LEED point)

90% of the area must then be between 300 and 3000 lux (to obtain 2 LEED points)

Thanks! It would be nice if the next diva version could either do this (to skip postprocessing, but it doesnt take too long), or, atleast, rename the option for "old" LEED 8.1 to something indicating which version of LEED it is refering to, to avoid confusion.

Best, Mathias

There's an update to this topic here:

http://diva4rhino.com/forum/topics/automatic-shading-not-working-wi...

Mathias Sonderskov said:

Just a follow up:

Using ladybug and grasshopper we've made the following GH definition to find an average of the irradiance values from the clearest days +/-15 days of equinox.

However, this custom sky is made based on direct normal irradiance and diffuse horizontal irradiance, whereas the LEEDv4 book suggests a sky made from direct horizontal irradiance and diffuse horizontal irradiance. I suppose it ends up in the same sky, but I am awaiting confirmation from LEED. (see thread from Jody: http://www.leeduser.com/credit/NC-v4/EQc7#comment-53203 )

Hope this helps anyone else looking for their parameters :-)

Best, Mathias

Diva Team,

Has there been any update to Diva to add in LEED v4 Option 2 calculations & display options?

I haven't tried the Grasshopper option discussed & updated above yet. But I'm wondering how to load the results since the LEED v3 results option uses 10-500fc.

The reason I want to use Option 2 in lieu of Option 1 is this particular building is that we are using Solatubes which, if I remember correctly, can only be modeled using the point-in-time simulations (not the annual).

Thanks!

Sandy

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