James,
LM-83 indicates that ASE values greater than 10% (when calculated with no shading applied) have unsatisfactory visual comfort even when manual shades are available to the occupant. It clearly states that ASE is computed without interior shading devices. LM-83 did not state that both sDA and ASE should be combined, but LEED made the decision to require both to achieve the maximum daylighting LEED points. If both of these are achieved, daylight conditions should be excellent, although the ASE metric can be met with 100% diffuse glazing, which might not be very pleasing for the occupants since views are eliminated. In my opinion, meeting the sDA+ASE LEED criteria will be very difficult, even when exterior shading such as an overhang is applied to a window. I believe the 10% ASE metric is total coverage across the entire building work area, so you can meet it with 20% of the points receiving direct sunlight on the south side of a building if the north side has 0% coverage and there is no east-west glazing. I believe the criteria are designed to promote the elimination of direct sunlight through a window that will result in little need for interior shades. Higher point totals are likely provided because it is difficult to meet.
I expect that most buildings will achieve the LEED daylighting credit by showing that 75% or 90% of the space has between 300 and 3000 lux at 9AM and 3PM on the clearest days around the fall and spring equinoxes. The challenge with this test is that blinds or shades are not applied in this analysis, so points with direct sunlight will likely receive greater than 3000 lux and will not count toward the coverage area. Reaching 90% coverage can be challenging since it, too, requires the elimination of most of the direct sunlight at two different times of the day. This option also promotes the use of daylighting design that applies exterior shading devices.
Rick
···
-----Original Message-----
From: James F Geers [mailto:[email protected]]
Sent: Tuesday, May 20, 2014 10:59 AM
To: [email protected]
Subject: Re: [Radiance-daysim] Using Daysim to demonstrate compliance with LM-83-12
Rick:
If the glare has to be calculated by the ASE 1000-250 with no passive shading devices, won't that force us to design spaces that effectively have no glare that needs to be controlled by the user. Of course I can use the dynamic shading model options in daysim to limit the glare as well, whether it is option 1 standard blinds or option 2 the dynamic model.
With that in mind will the work flow work?
The problem with your approach is that it does not accurately address the shading devices, which need to close completely across a window group to prevent direct sunlight from striking more than 2% of the work plane analysis points. Shading devices must be applied to obtain sDA according to LM-83. Penn State currently have a new module for DAYIMps that can do this, but it requires a slightly different header file format that is not 100% compatible with the GUI.
To correctly calculate sDA with a manual approach like you are trying, you can determine the direct sunlight values by running the model with the shades up and -ab set to 0. The points without sunlight will have values of zero. At any hours when the more than 2% of the points from this "-ab 0"
run reach 1000 lux, you apply the data from a full shade run, otherwise you use the data from an unshaded window. We are currently finalizing a new interface to address this and other advanced calculations, but it is primarily designed to analyze a single space rather than an entire building.
We are also working on a solution for an entire building, but that is perhaps 9 or so months from completion.
Rick Mistrick
Associate Professor
Penn State University
From: James F Geers [mailto:[email protected]]
Sent: Thursday, May 15, 2014 11:10 AM
To: [email protected]
Subject: [Radiance-daysim] Using Daysim to demonstrate compliance with
LM-83-12
I am trying to demonstrate compliance with LM-83-12 using the Daysim GUI 3.1 and would like a vetting of the following methodology.
To demonstrate sDA I ran the program on Scene Complexity 2 and ran the analysis with 300 lux as my DA threshold for a 10 hour day. Then checking the Daylight Autonomy I calculated the percentage of the space that had more than 300 lux 50% of the time to get my number of sDA300-50.
To demonstrate the ASE 1000-250 I ran the same model ( no blinds) with 0
ambient bounces (ab-0) and ran the analysis 1000 lux as my DA threshold for a 10 hour day. If the standard year is 365 days x 10 hours =3650 hours, 250 hours would be would be a DA1000 of 6.85% for no more than 10% of the sensor points would demonstrate compliance.
Until an updated script or Daysim GUI can calculate these values directly, I think this methodology should work. I am pursuing this path to utilize free of Daysim in conjunction with Sketchup.
Please let me know if I am missing anything.
JAMES F. GEERS | ARCHITECT, LEED AP: BD&C, ID, ND, EB, HOMES
513.721.0600 (x107) - DIRECT
SFA ARCHITECTS, INC.
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