One of the major features in cove.tool's growing capabilities is the Facade Guidance Tool for Daylight optimization. This feature allows users to quickly model and calculate the Spatial Daylight Autonomy sDA% for each orientation. A well-designed day-lit building is crucial for sustainability, as well these spaces typically use less electric lighting, require less natural resources, and reduce air pollution. Access to daylight has also been proven to have a positive impact on human behavior and health. Sufficient daylight has been shown to increase healing times in hospitals, improve students’ performance, increase productivity in the workplace, fight depression and lethargy, and even increase sales in retail environments.
How does it work?
Using an idealized room model to average the façade strategy of each orientation, the façade guidance feature will calculate and display the area of space which receives sufficient daylight over typical year in your climate. To learn more about the technical assumptions for daylight calculation, check the section Determining sDA% at the end of this article. This tool also allows for control over the of window sizes, location, and shading strategies. You can add fins, overhangs, obstructions, and change the glazing's visual transmittance all directly within the Façade Guidance Feature. The interface and feature capabilities are broken down below.
List of Feature Capabilities:
- N, NE, E, SE, S, SW, W, NW Tabs: The Cardinal Direction tabs allows users to open and edit each facade configuration based on their orientation. Only facades which have glazing in that orientation will appear in the facade guidance page.
- Daylight Model Viewer (3D Model): Users can use their mouse to move around the analysis model, zoom in to see their overhang and fin strategy, and zoom out to see the resulting daylight map.
- WWR% (Window to Wall Ratio): the measure of the percentage area determined by dividing the building's total glazed area by its exterior envelope area.
- Gear Icon (manual settings): Users can continue to manually input their facade details in the manual facade and context tool. Once inside users can specify overhang, fin, and context details. Once complete users can return to the facade guidance model, too see their sDA% and WWR.
- sDA% (Spatial Daylight Autonomy): describes how much of a space receives sufficient daylight. This metric is calculated by measuring whether a space receives enough daylight (<300lux/50% year) during standard operating hours (8 a.m. to 6 p.m.) on an annual basis on the horizontal work plane (0.76 m (SI)/ 30 in (IP) above finished ground).
- 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 which 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.
- Overhangs (#of Overhangs and Depth): Using the Number of Overhangs slider, users can add up to 8 horizontal overhangs. With the Overhang depth slider users can specify their overhang's depth up to 2.5m (SI) / 6.5ft (IP).
- Fins (#of Fins and Depth): Using the Number of Fins slider, users can add up to 8 vertical fins per window. With the fin depth slider users can specify their fin's depth up to 2.5m (SI) / 6.5ft (IP).
- Daylight Diagram and Legend: Helpful graphics to interpret what is being shown.
- Add and Remove Windows (#of Windows): These two buttons allow users to add as many windows as they want, or remove all the glazing from their facade.
- Window Dimensions (Height and Depth): By using the height and depth sliders users can customize the size of their windows. Be sure to select the window first (highlight in red), then apply changes. The WWR (Window to Wall Ratio) should automatically update as you edit the size of windows.
- Window Placement (Distance from Edge, and Window Sill): By moving these sliders, users can control the placement of their windows on each facade. To get an accurate sDA% make sure the sill height is accurately modeled in relation to the analysis grid. As a reminder, the facade guidance analysis model is an idealized analysis model that has scales the average strategy for the facade to fit a 8m x 2.7m (SI), 26.24ft x 8.85ft (IP) surface.
- Adding Obstructions (Distance and Height of Obstruction): User can model site context adding obstructions. Users can specify the distance from their facade the obstruction will be located and the obstruction's height. Height should be calculated by finding the average angle to horizon, learn more about calculating height in the Context tab of the manual settings (gear icon) page.
How would I use the facade guidance feature on my facade design?
The facade guidance feature is a rapid style analysis and guidance tool. The tool works best as the first step in a multi step process. As early stage analysis becomes integrated into everyone's workflow, these rapid style analysis tools are the key to testing dozens of strategies quickly and identifying where, when, and which strategy to follow up with in a more detailed analysis. Users have also found the tool useful for identifying shading' goldilocks ranges, where within 0.76m- 1.5m (SI)/ 3"-6" (IP) of fins or overhangs the addition of facade overhangs is best for energy and daylight. Also other users have found the not so grand benefit of shading on building energy use, which you can read more about in the article titled, How does shading impact design performance.
For those in search of specific configuration modeling tips, below is a guide various configurations. If you have a strategy that is not included below, please contact the live-chat support team for further guidance.
Cove.tool uses user-defined Envelope Geometry, the ASHRAE Standard 140, LEED v4 Reference Guide, and the IES LM-83 to determine the daylight calculations and methodology. See below to learn more about each daylight assumptions.
- Idealized Room Model: recreation of the ASHRAE Standard 140 – Base Case 600 Model using the 5.1.2 Geometry Convention.
- Room dimensions: 6 × 8 × 2.7 m = 129.6 m3 (SI), 19.68 x 26.24 x 8.85 = 4570.16 ft3 (IP). Read as room depth x width x height = volume
- Analysis plane height: 0.76 m, or 30 inches above floor
- Analysis grid size: 0.25 m2 (SI), 9.84 sqin (IP)
- Analysis period: 6am-8pm
- Meteorological year data: .epw from DOE, based on building location
- Glass transmittance: User-defined value, or 0.65 VT% (default)
- Surface reluctance: 0.2
- Illuminance threshold: 300 lux/50% year
- Calculation Method: 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)" with few modifications*. (*Ray-tracing for rendering daylight map)