Add Calculations - Daylight Factor
Daylight Factor is defined as the ratio of illuminance at a point on a plane produced directly or indirectly by skylight to the illuminance on a horizontal plane exposed to an unobstructed view of the sky. The method only takes luminous flux from the sky into consideration (not sunlight) and is generally used with uniform or CIE overcast skies (so that sunlight and solar position is not a factor). Daylight Factor is not calculated when electric lighting is switched on in AGi32 or when sky types other than Overcast or CIE General Sky Types 1-5 are selected.
Daylight Factor ( DF) = |
Horizontal
Illuminance from sky light on horizontal workplane
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Daylight Factor is used to determine what impact the geometry of the space and location and amount of fenestration have on daylight penetration. Some uses of Daylight Factor include:
- Comparing different geometric designs side by side.
- Meet certain requirements. For example, the United States Green Buildings Council (USGBC) promotes a Leadership in Energy and Environmental Design (LEED) certification for buildings. Part of the LEED criteria (prior to LEED 2009) specified that a Daylight Factor of 2% was required in 75% of the space occupied for critical visual tasks.
From the Add menu, choose Calculations - Daylight Factor, or from
the Calculations Toolkit select .
- Specify a unique label up to 32 characters long. The default label will be DF_1. Unless changed, subsequent labels will be DF_2, DF_3, etc. If a number is used for the label, subsequent labels will be incremented accordingly.
- An optional description may be entered up to 80 characters long. Meaningful descriptions that include room information and work plane height will be useful when generating schedules.
- Specify the point spacing from left to right and top to bottom. By default, a point spacing of 10 by 10 is used. As the point spacing changes, the text size adjusts, automatically. You may override the text size, if desired.
- You may center the measurement points within the grid boundary, if desired, by clicking in the selection box adjacent to Center Points Relative to Grid Boundaries.
- To calculate Illuminance values at the same grid locations (for reference purposes), click in the selection box Include Illuminance Grid. This selection is enabled by default.
- Specify the Summary options to calculate.
Daylight Factor Options |
Illuminance Options |
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Default Selections
Other available options
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Default Selections
Other available options
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- Select the display options, including precision, text color, perimeter lines, point markers and labeling.
- If desired, specify Isoline contouring and/or Highlight Values by clicking on the appropriate buttons.
- Creation Method: Choose whether to manually create boundary lines of Daylight Factor polygon or choose an existing line, room or object as the boundary line.
- If manually specifying polygon, the Z coordinate is 2.5 feet (0.7 m) AFF (work plane height) by default.
- If a tilted line, object or room is selected, polygon will be projected down to and created at lowest Z coordinate elevation.
- Click Ok. Follow the steps below depending on the selected creation method:
Specify a Polygon Manually |
Create Polygon from Drawing Entity, Room or Object |
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Notes:
Caveats:
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