An Experimental Evaluation and Comparison of Four Daylighting Strategies for Schools in North Carolina

Abstract

A comprehensive research study on the performance of daylighting systems at four schools in the Research Triangle area of North Carolina has been conducted during the three-month period from August through October of 2006. To achieve operational control, the experiments were scheduled over weekends when the schools were not in session. On a typical test weekend, daylight sensors and dataloggers were set up around the classroom after the students had departed on Friday afternoon and had to be picked by 7:00 am on Monday morning. Data was recorded every five minutes during daylight hours on Saturday and Sunday.

The experiments were designed to identify and quantify the positive and negative operating characteristics of each school and then compare their overall performance. In three of the four schools tested, the level of daylight available on a good solar day was found to be more than adequate for most of the day. However, one of the common problems at all schools was a lack of uniformity in daylight levels. This was particularly true for classrooms with south-facing glazing. Generally, the light levels at the front of the classrooms were too high and at the rear too low. This disparity in light levels is an issue that will have to be addressed in future designs. One of the pleasant surprises of this research was the excellent daylighting performance of classrooms with north facing glazing.

Daylighting is an exciting new development for school design and holds great promise for reducing the cost of lighting and air conditioning in schools. However, much work remains to be done to achieve a greater balance between the front and rear of the classroom and at the same time lower the overall light level. Related to the latter is the persistent challenge of providing the teacher with the ability to darken the room sufficiently for audiovisual presentations.