ASHRAE Journal - May 2009 - 31

These studies concluded that opportunities for energy efficiency existed, with on-site commissioning during set up being particularly cost effective.4 Research conducted by Lawrence Berkeley National Laboratory examined modifications to save energy but also evaluated the volatile organic compound (VOC) emissions from typical interior finish materials used in the manufactured modular industry. This analysis not only verified energy savings but also revealed that the transportation of classrooms to their respective sites often resulted in increased outgassing of interior materials, thereby reducing VOC concentrations.5 A much-discussed study done for the Pacific Gas and Electric Company suggested a correlation between classroom daylight levels and improved student academic performance and attendance levels.6 However, a more recent study shows weaker association, with window views and the acoustic environment being more important than daylighting.2 In previous work, the Florida Solar Energy Center (FSEC) studied retrofits in two existing portable classrooms in central Florida demonstrating the potential to reduce measured energy use by 40%. This was achieved by improving heat pump efficiencies, integrating ERV (enthalpy recovery ventilator) and changing to a highly reflective roof.7 In separate simulation analysis, FSEC evaluated potential improvements to new portable classrooms across U.S. climates.8 A building energy simulation tool was created to model the energy performance of relocatable classrooms in varied climates in the United States. Modeling results were used within this demonstration project to determine the most effective modifications for testing. Specifications of Experimental Classrooms classrooms constructed in a factory and delivered to school sites. They are designed to use less energy, potentially improve indoor air quality, and provide enhanced levels of natural lighting. The research consisted of three different case studies in three different climates, requiring three different sets, of specifications. All exceeded the minimum building and energy code. Most relocatable classrooms in the United States are 24 ft × 40 ft or 24 ft × 36 ft (7 m × 12 m or 7 m × 10 m) units with a conditioned floor area of 860 to 960 ft2 (80 m2 to 89 m2). However, regional and local building codes create different specifications. FSEC located matched pair units in three different climates. One pair of classrooms is in Cornwall, N.Y. (cold climate), Chapel Hill, N.C. (mixed climate), and Orlando, Fla. (hot-humid). The standard classroom is typical in specifications for each location. In contrast, the experimental PERC unit used the research strategies mapped out from the previous analysis.8 The New York and Florida portables were elementary classrooms, while those in North Carolina were occupied by high school students. Within each location, the hours occupied and occupancy levels between the side-by-side comparisons exhibited little deviation. Monitoring Results These three case studies described in this report were sideby-side comparisons in three climates and became known as the performance enhanced relocatable classrooms (PERC) project. This research looked at specifically designed modular Beginning in fall 2002, six classrooms (two in each climate) were constructed, sited, instrumented, and monitored for performance. Detailed 15-minute data were obtained including enduse energy, meteorological conditions, and interior classroom conditions for temperatures, humidity, CO2 concentrations, and light and noise levels. As is typical, all of the classrooms were all-electric with measured end-uses including total classroom electrical demand, lighting loads, air conditioner, strip heat/heat pumps and bathroom heaters where applicable (each classroom has a bathroom). Miscellaneous electricity used for plug loads were obtained by differencing the total recorded site electrical use from the recorded energy use of the various submetered major appliances. The portables are located side-by-side at Willow Avenue Middle School in Cornwall, N.Y., about 50 miles north of New York City. These units consist of two classrooms each (24 ft × 34 ft [7 m × 10 m]) attached end-to-end. The control and experimental portables are 24 ft × 68 ft (7 m × 20 m) with 1,632 ft2 (151 m2) of conditioned floor area. Cornwall, N.Y., is a heating-dominated climate with 30-year normals showing 6,848 heating-degree days and 507 cooling-degree days. Energy Savings. Figure 1 shows the average electrical load shape describing the energy savings for the entire school year over a 24-hour cycle from November 2002 to June 20, 2003. The measured overall energy savings of the PERC was 48 kWh/day or 36%. Most of the savings were concentrated in the evening and early morning hours when the heating system was operating May 2009 Figure 1: Electric energy demand profile. at its maximum. Note that the average peak electrical demand of the experimental unit at 8 a.m. is more than 2 kW (20%) lower ASHRAE Journal 31

ASHRAE Journal - May 2009

Table of Contents for the Digital Edition of ASHRAE Journal - May 2009