## Cylindrical Illuminance and Modeling Effect

Cylindrical illuminance (Ez) is the average of the vertical illuminance computed in the four Cardinal directions (N,S,E,W). Modeling Effect is the ratio of cylindrical illuminance to horizontal illuminance at the same point. These metrics are required by British Standard document BS EN 12464-1:2011, Lighting for Work Places: Part 1 - Indoor Work Places.Typical work plane heights are 1.2 meters for sitting tasks and 1.6 meters for standing tasks (approx. 3.94' and 5.25') although the software will allow any value to be used.

Both Cylindrical Illuminance and Modeling Effect are available from the Metrics menu on the ElumTools toolbar. They are available separately to allow separate tracking of the two metrics when both are calculated for the same calculation point instance.

Selecting the Cylindrical Illuminance or Modeling Effect calculations

This can be achieved in two ways: by setting the Metric from the Metrics menu on the tool bar to the desired metric, or by selecting the metric from within the Metrics section of the Add or Edit Calculation Points dialogs. When selecting the Metric from the toolbar menu it will automatically be selected in the Add points dialog when adding a new calculation point instance. If you want both Cylindrical Illuminance AND Modeling Effect to be computed you must select the second metric within the dialog. You can see the results for the respective metrics after calculation by selecting the Metric from the toolbar.

Calculation point spacing

ElumTools uses an optional calculation point spacing algorithm to ensure the point spacing meets the requirements of BS EN 12464. The check must be enabled from System Settings (set Validate Calc Point Spacing to True).

 The internal check is designed to warn against points that may be too far apart to yield informative results for the lighting application. This check happens when you attempt to close the Calculation Points dialog.   The spacing check formula is based on British Standard document BS EN12464*. If the point spacing falls outside of the formula boundary, ElumTools will respond with the choices shown in the dialog to the right and discussed below. • Option one (on top) is rounding down from the formula result to the nearest whole number and is the recommended choice.

• Option two (middle) is the exact result of the formula calculation.

• Option three (bottom) is the value you have entered.

The BS EN12464 standard recommends calculation point spacing based on the following formula:

(metric meters) Point spacing = 0.2 x 5log10(d)

(Imperial feet) Point spacing = 0.286 x 5log10(d)

d = the longer dimension of a rectangular grid, in meters or feet

Notes

• For rectangular grids, d is the longer dimension of the calculation area. However, if the ratio of the longer to the shorter side is 2 or more, then d becomes the shorter dimension.

• For non-rectangular girds, the XY-axis aligned bounding box of all geometry is used to determine d.

Enable the check

The calculation point spacing check is disabled by default but can be enabled from System Settings by setting the Validate Calc Point Spacing to True. 