"Impossible" to achieve option 2

Did you  design the project to meet the daylighting requirements?  If you do not have performance goals established at the beginning of the design process and do not check to ensure that those goals are being during the design process then you are setting your project up for a yes or no result at the end of the design.  Just following a set of good rules of thumbs will not always provide you with the results you want or need, it is a start but only simulations during design will ensure design decisions are meeting the requirements. 

If noted you have automated blinds, so why are not doing option 1? 

Its not unfair, the work of the Committee for Daylighting for IESNA was composed of many people in the daylighting profession with many years and projects. They established these requirements based on alot of work, studies and experience. Not every project can meet it. An like i said, if you just did simulations at the end of design to determine compliance, you can;t blame anyone or anything but yourselves for not ensuring your design met the requirements.

Todd,

LI#100002149 accepts dynamic shading for Option 1. We just assumed it is acceptable for Option 2 - is it? 
If it is, Option 2 could quite reasonably be achievable if there is adequate daylight penetration.

thanks,

Option 2 does not. But you noted that the project has automated exterior shading, correct? Option 2 notes to exclude blinds or shades, but exterior shading would be a exterior shading device, not interior.  I would model  with the automated shading positioned to handle the worst case scenario. If it still is not meeting the requirement i would try option 1.  You need to adjust the blind properties in whatever program you are using to represent the properties of the exterior shading as best as possible. 

Have you checked the number of bounces in your simulation program. IES LM 83 inidcates a setting of 5. Not sure what you are using, but if you have more than 5 bounces you show might higher than normal values. 

Hi Sarah, Deborah, Todd!

Sarah, per Todd's suggestion, LEEDv4 Option 1 removes the ASE Penalty if you are using automated systems.  Please check out this LEED Interpretation:

• Additionally, spaces with an automated dynamic façade system* OR spaces smaller than 250 square feet are exempt from the ASE requirement.

Deborah, this new allowance should encourage more use of Option 1 and automated systems since as you noted, it will remove high values (but will still not get the team exemplary credit).

Option 1 also gives up to 4 points (1 is for exemplary credit) versus 2 points for Option 2.

Option 1 is a more robust way of analyzing daylight, correlating with field studies of occupant preferences.  Option 2 is simplistic, similar to LEED 2009, hence a transition to new metrics like Option 1.

From my experience, both Options 1 and 2 are achievable for teams that use tools that accurately compute sDA and ASE early on and iterate.   

I agree that Option 1 is extremely detailed to get right, but there are software tools that accurately prepare a model and compute both Option 1 and 2 with a single click.  You can use this information for both "getting LEED points" and improving your design.

I sincerely hope you encourage your clients to employ natural light in their designs.

I highly suggest you read IES LM 83.  It states, to include surrounding buildings, how to model windows and openings along with including external shading devices for your simulations. If its an external shading device, regardless of whether its automated or not, you should include it in your simulation.  IES LM 83 is the standard referenced and confirms that you can use the external shading system. 

Sarah,

Yes, for you can still get high ASE scores with automated shades (internal/external) with Option 1, but not get the exemption in the addendum.  You will not be able to get exemplary credit with an automated system with high ASE. The reasoning is that if the automated system fails, its not going to be as robust as a fixed design/system that eliminates glare.  So the metric encourages designers to use passive techniques to block unwanted sun first, but also recognizes the value of automated facades.

I will explain in more detail my full quote:

• I agree that Option 1 is extremely detailed to get right, but there are software tools that accurately prepare a model and compute both Option 1 and 2 with a single click.  You can use this information for both "getting LEED points" and improving your design.

I disagree that you have to build a second model to compute an accurate Option 1 score.  Architects, engineers, others can use their detailed design model (assuming it doesn't have light leaks like forgetting to put on a roof :) so this is not expensive to do.

I also disagree that its "peanuts" to compute :).  See Andy Mcneil's method to accurately calculate climate-based annual simulations with buildings with complex fenestration (e.g. blinds and shades).  There are many challenging areas to implement this simulation method correctly (e.g. from how to correctly calculate light for atrium spaces to just really detailed details "In order to avoid mirror specular reflections, we can create a new material file with specularity of all materials to be set to zero, however later we will need to change all materials to black for similar reasons (see section 4.1) so for simplicity we will change materials to black here too").  As well as sections of IES LM-83 on blind operation and window grouping are non-trivial problems.

Running Option 2 on a model with paper-thin walls without modeling the ergonomics of how people or electronics control blinds can ultimately cost more to achieve exemplary design, since after its constructed it can have non-optimal performance and a retrofit may be needed.

So do you have any more reservations for trying Option 1 yet?! :).  

Hello, do you have an answer for the Sarah's question: "This still leaves the question open about option 2: can I take into account external shading devices for the Simulation?", please?

Best Regards