AnnuOWL | Annual evaluation of Occupant Wellbeing through Lighting

This is the documentation of AnnuOWL: an opensource workflow in Rhino Grasshopper developed for performing Radiance-based annual lighting simulations on horizontal and vertical planes, and evaluating visual and non-image-forming effects of light on occupant comfort and wellbeing, along with energy performance via metrics for light sufficiency. AnnuOWL can support early stage interventions in lighting and facade design.

This tool requires minimal inputs from the user when evaluating the following metrics on an annual basis: Lighting Sufficiency (using editable recommendations of EN17037 for spatial daylight autonomy), Non visual/circadian potential (using annual hourly evaluation of Circadian Stimulus, a metric proposed by Lighting Research Centre), and Protection from Discomfort Glare, (using editable recommendations of EN17037 for glare protection using DGP as a metric). These metrics are displayed in an intuitive visualisation proposed as OVNI diagrams, and can help in design intervention through visualising metrics of occupant [Visual] comfort, [Circadian] health and energy use for lighting.

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The workflow of AnnuOWL

As input, AnnuOWL needs building geometry, weather data (as *.epw file), and pre-calculated annual spectral data as (*.aowl file).
Parameters such as occupancy schedule, table height, head height, grid distribution, and thresholds for metrics to be evaluated are pre-populated with standard defaults, but are editable to match user needs. With these inputs, AnnuOWL can evaluate:
-> Grid-based CBDMs (DA, cDA, UDI) and Average illuminance through occupied hours.
-> Occupant-centered DA performance (High/Med/Min/NC) at table height using (editable) EN17037 target thresholds.
-> Occupant-centered Circadian potential as non-visual performance (High/Med/Min/NC) at eye-height in four orientations.
-> Occupant-centered Protection from discomfort glare (High/Med/Min/NC) at eye-height via (editable) EN17037 thresholds.
-> Annual grid-based Spatial Daylight Autonomy compliance throughout floor area (High, Minimum, Medium).

The OVNI diagrams

The OVNI diagram is an infographic placed at every occupant's position, which describes the occupant-centered annual performance of the design towards energy use, comfort, and circadian health.
Each OVNI includes a hemisphere, surrounded by three rings. Each ring is sub-divided into four segments, facing N,E,S,W orientations.
-> The hemisphere represents sufficient illuminance at table height, and uses radiance grid-based evaluation for occupied hours.
Sub-divisions on the rings represent vertical viewing positions for four principal orientations, evaluated at the occupant eye-height.
-> The inner ring represents Circadian potential & Non-visual performance, as proxy for occupant health & well-being.
-> The middle ring represents protection from discomfort glare for each orientation, and describes occupant comfort.
-> The outer ring represents view quality. This is yet to be incorporated, and will describe occupant satisfaction.

Grid: Climate-based Daylight Metrics

Using slider input, users can visualise Daylight Autonomy (DA), continuous Daylight Autonomy (cDA), useful daylight illuminance (UDI) or average illuminance through occupied hours, on a horizontal grid. With pre-populated standard default values, users can edit thresholds for CBDMs (DA, UDI_lower, UDI_upper), occupancy hours (start of business, close of business, days per week, weekend offset), and grid definition (x-spacing, y-spacing, height above floor) to match specific demands.

OVNI | Hemisphere: Daylight Provision

Daylight autonomy through occupied hours, in 4 bins of High, Medium, Minimum and Non-compliant is evaluated on (editable) table height. OVNI displays compliance for each location (High/Medium/Minimum, Non-Compliant) across minimum (editable) occupied hours. Defaults are EN17037 target thresholds: 750, 500 and 300 for High, Medium and Minimum, but users can edit these thresholds when evaluating for other standards, or to match future updates in the standard.

OVNI | Inner ring: Non-visual/Circadian Potential

Circadian Stimulus is evaluated separately for 4 orientations for each occupant position at (editable) eye-height, via Truong's approximation, using vertical illuminance and pre-calculated hourly CIE tristimulus z value (from *.aowl file). The CS sufficiency during morning hours for every (editable) occupied day is binned into High/Med/Min/Non-Compliant based on (editable) thresholds, and the OVNI ring segments visualise compliance for each view-point across minimum (editable) occupied days.

OVNI | Second ring: Protection from Discomfort Glare

Hourly DGP is also evaluated separately for 4 orientations for each occupant position at (editable) eye-height, via simplified DGP approach, using hourly vertical illuminance. Protection from glare across (editable) occupied annual hours is binned into High/Med/Min/Non-Compliant based on (editable) EN17037 thresholds: 0.35, 0.40, 0.45, >0.45 for High/Med/Min/Non-Compliant. The OVNI ring segments visualise compliance for each view-point across minimum (editable) occupied hours.

Annual Heatmap: CS and DGP

Annual heatmaps of CS and DGP can support time-specific investigations. This can help in designing facades that minimise discomfort glare at specific times, or schedule complementary circadian lighting in supplementing non-visual needs. To perform such in-depth analyses at occupant level, users can indicate occupant position-of-interest (using slider input), and AnnuOWL will generate annual hourly heatmaps (365 x 24) for CS and DGP, across four orientations for the selected position.

Legend: SDA Compliance

This singular grid-based compliance metric across the entire facility can be used to report the lighting performance towards sufficiency and daylight autonomy. Although with pre-populated standard defaults, occupants can modify grid definitions, occupancy hours, thresholds for Min/Med/High and definition of minimum occupied annual hours, in generating this metric. Similar metrics can also be designed for CS and DGP as 'percentage of occupants'.