Performance of the 21-Inch Unit

Our 21-inch unit is designed for ceiling heights of 12-14 feet, and workspaces of 300-400 square feet. Based on our thorough testing, the performance for the principal clear days throughout the year is shown in the graph above. For comparison, the performance of a conventional cylindrical tubular skylight is also shown.

Three Times as Much Light

The bar chart shows the annual-average light output for the 21-inch unit for 100% clear days. This output number must be multiplied by the appropriate clearness factor for the region where the unit is installed. For Keller, Texas, this factor is about 65%. For comparison, the same annual-average light output is shown for a conventional cylindrical tubular skylight. Note that the new unit outperforms the old unit by a factor of three for a latitude of 33 degrees. This advantage is even greater for higher latitudes, about a factor of four for a latitude of 45 degrees.