ENERGY PERFORMANCE OF DAYLIT SCHOOLS IN NORTH CAROLINA
Michael H. Nicklas
Gary B. Bailey
850 West Morgan Street
Raleigh, North Carolina, 27603
The following study analyzes the energy performance and cost of daylit schools designed by Innovative Design in Johnston County, North Carolina. The analysis compares the first-year energy performances of the Clayton and Selma Middle Schools and the K-5 Four Oaks School with similar but non-daylit schools in the County. The two daylit middle schools were completed in the spring of 1993 and the comparison year was July of 1993 through June of 1994. The Four Oaks School was completed in August of 1990 and the first year of collected data was 1991-92.
In addition to the three daylit schools listed above, cost information is also provided on two other daylit schools designed by Innovative Design – the Durant Road Middle School (Wake County, NC) and the Clayton Elementary School (Johnston County, NC). The Durant Road School was completed for the opening of the 1995-96 school year and first-year energy data is not yet available. Clayton Elementary is now under construction and nearing completion.
The K-5 Four Oaks School was constructed on an existing campus when the majority of the old school burned. Escaping the fire were classroom facilities that still serve the needs of the middle school students and a gymnasium which was integrated into the new K-5 construction. The renovated gymnasium as well as the cafeteria and outside athletic facilities are shared by both the K-5 students and the middle school students.
The two daylit middle schools are very similar in design, both based on a prototype design that incorporates extensive south-facing roof monitors. However, the Selma Middle School is approximately 22,000 square feet smaller and houses 150 less students. The Durant Road Middle School, although much larger, also includes many of the same design features incorporated in the Clayton and Selma Middle Schools. However, Durant utilizes both north and south facing roof monitors. The Clayton Elementary School is considerably different in design but also utilizes south-facing roof monitors as the major daylighting strategy.
In all cases, translucent fabric baffles are suspended in the lightwells to eliminate any direct beam radiation from entering into the work area below. Light sensors are used at each of the schools to stage the backup lighting. All of the schools are designed to achieve in excess of 70 footcandles, through daylighting, over two-thirds of the time the schools are occupied. Each classroom is also equipped with shades that can be used to darken the spaces and override switches to increase lighting levels. Although the shades and lighting override switches provide occasional functional benefits for individual classrooms, they are also the source of reduced daylighting benefit in certain classrooms.
The schools used in the comparison had, at the time of the analysis, the following characteristics:
the majority of space at each school was air-conditioned;
the schools were within the same County (a several county region was used in comparing cost of construction);
the majority of the space within the school was being utilized; and
the grade levels were similar.
1. CHARACTERISTICS OF THE DAYLIT CLAYTON AND SELMA MIDDLE SCHOOLS AND COMPARISONS TO NON-DAYLIT SCHOOLS
Although attempts were made to compare the daylit schools to similar schools within the County, there were several significant energy related differences. Although the daylit schools performed extremely well, the following factors significantly increased the energy consumption and made the comparisons closer than otherwise would have been the case. Energy consumption in the daylit schools was abnormally high because:
the Clayton and Selma schools were the newest (and daylit) and they were utilized much more for extra-curricular activities and community events, accounting for considerably more night-time and weekend use;
the gymnasiums were extensively used during the summer and at night;
the schools were equipped with individual classroom TV/video monitors and communication systems;
more electrical equipment and computer technology was incorporated into the schools;
in the Four Oaks case, the gymnasium and cafeteria were shared with a middle school; and
the newer schools required considerably more fresh air make-up.
Both Clayton and Selma had central, natural gas boilers for heating and Four Oaks heating was with oil.
In all cases it appears that, even though the schools were not designed as year-around schools, they were occupied (at least by staff) most of the year.
2. THE COST OF DAYLIGHTING
The following lists both new daylit schools and non-daylit schools constructed in the immediate, several county region of North Carolina during the timeframe of our study. Taking into account the general trend of greatly escalating school construction costs, the daylit schools are very comparable. The highlighted schools indicate daylit schools designed by Innovative Design since 1990. In addition to the Clayton and Selma Middle Schools and the K-5 Four Oaks School, we have also included cost data on the Durant Road Middle School for Wake County and the Clayton Elementary School for Johnston County.
In all of these schools the cost of the daylighting components have added little to the first-cost of the projects. In the Durant Road Middle School the owner was particularly interested in calculating the energy cost versus savings attributed to the daylighting schemes employed. Through extensive cost estimating by an independent construction cost estimating firm, it was determined that the added cost of the daylighting features totalled $230,000. However, when one accounts for the $115,000 in mechanical equipment and electrical system downsizing possible because of the cooling and lighting load reductions, the net additional cost to the project was $115,000 – less than 1% of the total construction budget. The overall project, when completed, was 5% under budget and the daylighting/energy investment (when compared to typical new middle schools in the area) will be returned to the school system in less than a year.