Daylight Analysis - sDA + ASE

sDA, ASE Daylight Feature, Daylighting details, LM-83 methodology

Patrick Chopson avatar
Written by Patrick Chopson
Updated over a week ago

cove.tool automates the process for a full floor sDA & ASE daylight study with highly complex Revit, Sketchup, & Rhino/Grasshopper models in minutes (as compared to a few hours that it takes other platforms).

What is sDA?
Spatial Daylight Autonomy (sDA) is a yearly metric that describes the percent of space that receives sufficient daylight. This analysis type is a precise metric that must meet the required parameters in order to determine the building's daylight performance. To elaborate, sDA (Spatial Daylight Autonomy) describes the percentage of floor area that receives at least 300 lux for at least 50% of the annual occupied hours (8am-6pm) on the horizontal work plane (30" above the floor or work plane height). The legend in the lower right side shows that yellow just meets the requirement and means that 50% of the year this point passes.

What is ASE?

Annual Sunlight Exposure (ASE) refers to the percentage of space that receives too much direct sunlight (1000 Lux or more for at least 250 occupied hours per year) at the work plane height, which can cause glare or increased cooling loads. Green is passing. All other colors are the degree of failure. Below is the legend.

I uploaded Geometry before Nov 1st. 2019 Why do I need to re-upload?
There are new data categories we need in order to run the full building daylight simulation. This is only done by using the latest 3rd Party plug-ins. Version (v2.0) and every subsequent update collect mesh data and coordinate information which is used to create the analysis model in cove.tool.

Why do early-stage daylight modeling?
Early-stage daylight modeling allows our users to quickly understand the impact of various design decisions on the spatial daylight autonomy of the space. Research highlights the benefit of daylight in health, happiness, and productivity. Always get your daylight and glare situation right before proceeding to energy.

What is our Calculation Method? Is the daylight method accurate?

Taken from "LEED v4.0 - IEQ c7 Daylight, Option 1. Simulations: Spatial Daylight Autonomy" and "IES LM-83: Approved Method: IES Spatial Daylight Autonomy (sDA%) and Annual Sunlight Exposure (ASE)" Cove.tool runs a full ray-tracing simulation and is calibrated to within 1% to 5% of a DIVA Radiance simulation. The raytracing engine improves speeds by 1500x to 500x by employing new statistical methods, machine learning, and parallelizing the calculations on our back-end server environment. This allows us to have multiple 3D Analysis Types calculated simultaneously for every floor.

Environmental conditions are based on the Tregenza sky constructed from the weather file with 576 subdivisions. We use a 3 phase method for maximum accuracy that compares with a 6 bounce method in Radiance. To speed up the simulation we keep the reflectivity percentages (materiality) fixed with the following assumptions: Floors 20%, Interior Walls 50%, Ceiling/Roof 70%, Exterior Façade (shading devices, mullions, light shelves, etc.) 50%, and exterior Walls 35%, Outside Ground 40%. This allows any user to construct a realistic simulation and avoids "cheating" the simulation with incorrect inputs. This is also the correct settings for a LEED daylight analysis.

How does it set up the model?
In a daylight model, there are a few factors that are key to determining the impact of daylight on your building including:

1. Location: The sky dome, which represents the amount of light that emanates from the sun, the sky, and clouds, is auto-created and loaded for any location on Earth. In cove.tool, this is done automatically for you as soon as you enter a building location. This input generates site context needed to accurately replicate the conditions of your project.

2. Geometry: we pull in the Geometry directly from your 3D model using the cove.tool plugins for Revit, Rhino/Grasshopper, and Sketchup. The geometry is pulled out in various layers for glass surface, wall surfaces, floor surfaces, roof surfaces, shading structures (which can include overhang, fins, light-shelves, and site context). Important: To represent trees upload boxes instead of complex foliage. The geometry is then accurately represented within the web-app.

3. Grid Size: The grid size as a measurement unit in ft/m represents the size of the analysis grid on which the simulation is done. The smaller the grid size, the slower the simulation. We autoruns at a 6 ft grid but can be modified by the user down to 2 ft for a LEED level daylight grid. There is only a slight change in accuracy between grid sizes so if you want a fast idea the larger grid size is perfectly acceptable for early stage decisions.

4. Visual Transmittance (VT%): Visible transmittance is the amount of light in the visible spectrum that passes through a glazing material. Using the Visible Transmittance (VT%) slider, users can control the amount of daylight that passes through their windows. A higher VT% means more daylight penetrates the interior space which, can directly impact electric lighting and its associated cooling loads. NOTE: SHGC and U-Value for Glazing materials can be changed on the Baseline Energy Page.

Note: cove.tool uses Visual Transmittance (values from 0 - 1) which is interchangeable with Visible Light Transmittance (VLT) which typically ranges from 0 - 100. A VT of 0.9 is equal to a VLT of 90.

5. Rotation Angle (°): Users can use this input to rotate their daylight model. Notice that the blue vector on the daylight grid indicates the North direction, and by entering a rotation angle will re-orient their project x-degrees clockwise from North. This input will be useful for a user who has Site North differing from the BIM Project North, or in the case of an orientation/massing study.


1. Can I submit this for LEED compliance?
Yes, our calculation method follows the guidelines required of the BD+C LEED v4.0 IEQ - Daylight credit for sDA% and ASE% simulations. However, buildings with dynamic facades can not pursue LEED compliance with cove.tool, as that is yet a capability inside the daylight page and upload process. A user would need to simulate a dynamic façade in another tool and then apply an effective visual transmittance to simulate a dynamic façade in our platform. Also, note that users must denote unoccupied areas from the floor plate during upload. That means occupied spaces can be uploaded regularly as Floor objects, and unoccupied areas should be uploaded through the Shading Device Layer. Check out the LEED Daylighting Documentation article for the full steps.

2. Which direction is North?
TopRight of Model space has a North Arrow (indicator/button). Click is to reset bearing to North, or refer to it when orienting yourself.

3. How do I navigate in the Daylight Page? Orbit, Zooming, Panning?
This article includes a video tutorial and a written guide for all features of the navigating 3D Mode in cove.tool.

4. Is the sDA/ASE maps meant to be so blurry and/or pixelated?

Pixelation is a direct result of the design of the sDA/ASE calculation method. This means the simulation is more accurate. Seeing the grid size validates the accuracy of the simulation. Each grid point on the floor plan denotes a square area of space that is analyzed to determine the amount of %sDA or %ASE it achieves. Users can increase or decrease the grid size for more detailed maps. However we do place the 2'x2' grid limit, not only to keep simulations running fast but also this is the smallest and most common industry standard for daylight and glare heat-maps. If we made the grid size 2"x2", we could probably have a seamless gradient, but the operation would be overtly detailed and take hours or days to complete. Also, the coloring of each grid point indicates a range of performance. Use the legends below to interpret the performance of each point in your floor plan. For daylight, the colors are warm when space is considered daylit (300 lux or higher for 50% of the occupied hours), vs darker colors which are areas not receiving sufficient daylight. Also, each color is a 10% sDA range, slowly climbing up. The same goes for ASE but in terms of occupied hours.

5. Can I upload Trees with the plugin?

Yes, but the geometry must be incredibly simplified and exported only through the shading device layer. Blocks or single plane cut-outs should suffice. If a user uploads a complex tree object, the daylight sequence may take hours or days to complete. Examples of complex geometry would be tree objects for renderings which include millions of small triangles to reflect every leaf and bark surface. Read more about geometry to avoid in this article.

6. How do I generate the LEED report?
Through the Room Assignment tab on the Geometry Page, you can follow the process outlined here.

7. Is there a way to analyze SDA and ASE for summer solistice and winter solistice in covetool?
Solstices are for the older version of daylight analysis before there was computing capacity to look at the whole year. cove.tool's sDA and ASE allows you to design for the whole year instead just one day.

8. How can I model a lightshelf in cove.tool?
To create a light shelf in cove.tool, you will upload your model using one of our plugins from a 3D modeling tool and make sure that the light shelf is filtered into the cove.tool roof view/tag. The light shelf will then be exported to cove.tool as a Roof element to capture the required behavior in the 3D Analysis. Since this will slightly impact your baseline energy calculation, we suggest having a dedicated copy for 3D Analysis of the daylight. The light shelf surface (represented by a roof) will have a fixed reflectivity (materiality) of 70%.

9. Is there a good place to place exterior overhead doors for a warehouse for accurate results?
To model overhead doors, categorize them as spandrels through the plugin.

10. How do I model topography?
You can model your topography as single surface and export that geometry as shading device.

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