SPOT Case Study - Classroom #1

Test Classroom #1 is a narrow space, oriented 20 degrees East of South. Windows on the south wall are associated with shade control zone 1, while the window on the East wall is associated with shade control zone 2. The translucent windows on the North side of the building do not have any additional solar control devices.

Input

Aperture

Two electric lighting zones are defined for separate photosensor control.

Light Input

All variables remain as default values except for the shade transmittance, which is lowered to 5%.

Advanced Options

Site and usage information is selected.

Usage

The shades for the South windows (Zone 1, as previously defined) are given automatic controls. The sensor position can be entered manually, but in this instance, the position is determined by first selecting the South wall from the drop down menu and then clicking on the "Generate Selected Sensor Position" button. The setpoint is also generated automatically. Since it is difficult to provide solar control on the East façade of a building, the East window (Zone 2) is given fixed shades, which will be considered down for all calculations.

Shades

With the Light Loss Factor set to 0.8, the design illuminance of 30 footcandles is met over a majority of the workplane.

Electric Lights

As expected, the low transmittance shades block a great deal of the low morning sun entering through the South and East windows. The translucent North windows help provide a low level of ambient daylight throughout the space.

Daylighting Results

Due to the building orientation and fenestration selection, it can be seen that the Southwest corner of the room will receive the least daylight contribution during most hours and days of the year. This page also proves a reminder and/or connection between the selected location in terms of latitude (which is displayed on the Site and Usage page) and the location's climate.

Daylighting Results - detailed

Test Classroom #1 provides copious amounts of diffuse daylight, without allowing direct sun to penetrate the façade. This circumstance awards the space with a Daylight Autonomy evaluation of "Excellent Daylighting".

Daylighting Report

Sensor_1 and Sensor_2 placements are the recommendations given by SPOT. As can be seen by the lighter colored regions in each Correlation to Zone plot, SPOT shows optimal placement in the annular region surrounding the electric lights. Additional sensors are placed by the user in each zone to test the affects of 45-degree Cosine sensors and Open Loop sensors on energy and cost savings. Sensors 1b and 2b are defined as free standing (F) so that they can be placed on the exterior of the building for Open Loop control.

Photosensor - generator

Photosensor - #2

The positive feedback given in the Daylighting Report is reinforced in the Photosensor Analyzer page by the strong linear correlation between photosensor response and workplane illuminance during sunny conditions, for both zones. With the SPOT photosensor placements of Sensor_1 and Sensor_2, the average workplane illuminance will range from about 30 to 100 footcandles, and occasionally drop below the 30 footcandle criterion.

Photosensor - Analyzer

Photosensor - analyzer #2

The energy and cost savings for one similar space, with the Cosine sensor and Continuous Dimming control system are given in the Annual Results charts.

Results

In addition to comparing the energy and cost savings tables, Daily, Hourly, and Detailed Results for the workplane should be reviewed on the Annual Analysis page to ensure an overall acceptable daylighting design.

Results - 2