• Portable Classrooms

This is primarily a WSU (and its subcontractors Oregon and Idaho) and Pacific Northwest National Lab (PNNL) task.  Other partners include FSEC, UCFIE, the State Energy Offices of Oregon and Idaho, school districts in Portland, Oregon, in Boise, Idaho and Marysville, Washington, regional utilities, manufacturers, and other stakeholders in the Pacific Northwest.

The objective of this task is to promote the adoption of energy efficient portable classrooms in the Pacific Northwest that provide an enhanced learning environment, high indoor air quality, and  both substantial and cost-effective energy savings.  BAIHP staff focus on four main goals: (1) offering technical assistance to portable classroom manufacturers, school districts, and related organizations, (2) field assessment, monitoring, and analysis of innovative building technologies and energy saving features to determine their value, (3)  facilitation of collaborative agreements among regional utilities, northwestern portable classroom manufacturers and materials and equipment suppliers, as well as school districts, and state education departments and their affiliates, and (4) conducting and creating educational opportunities to advance the widespread adoption of energy efficient portable classrooms in school districts nationwide. 

The experiences working on the energy efficient portable were instructive, particularly in the identification of flaws in portable classroom design.  The difficulties that BAIHP staff encountered demonstrate the importance of well-defined commissioning protocols, documentation, and coordination among all personnel that service and install HVAC equipment.

Findings:

• Portable classrooms in the Pacific Northwest are occupied about 1225 hours per year, or about 14% of the total hours in a year.
• The average number of occupants in the standard 28' x 32' portable classroom provide an internal heat of about 480 kWh/year, or 8% to10% of space heating requirements.
• Most of the heat loss in portable classrooms manufactured after 1990 occurs by air leaking through the T-Bar dropped ceilings, because they have no sealed air/vapor barrier.  This newly created phenomenon occurred with the incorporation of the less expensive dropped T-Bar ceiling in place of the more expensive sheet rock used in older portables. Air leakage also is increased because of unsealed marriage lines - now used as a low cost method of meeting the state attic ventilation requirements.
• Since all portables tested in the project used a simple seven-day programmable thermostat, the HVAC systems operate during vacations and holidays.
• Energy codes in Washington, Oregon, and Idaho are high enough to make beyond-code envelope measures non cost-effective.
• Older portable classrooms under removal consideration, could be retrofitted with new energy efficiency measures at much less cost than purchasing a new portable classroom. Installing low-E, vinyl framed windows, insulated doors, T-8 light fixtures, and caulking and sealing air leaks can all be cost-effective when refurbishing older portable classrooms.  HVAC system replacement in older portable classrooms will be the biggest single cost item, ranging from $4500 to $6500.
• CO₂ sensors appear to be unreliable as a control strategy.  Those installed by field crews and monitored by dataloggers in this study did not match the readings shown by the CO₂ sensors which controlled the ventilation systems.

Based on data analysis from years one through four, the following measures were recommended.  New portable classroom procurement, setup, and commissioning as well as existing classroom retrofit guidelines produced by the BAIHP study can all be found in Appendix A.

Recommendations:

• Install 365 day programmable thermostats in all existing portables and specify these thermostats for new construction.
• In portable classrooms constructed with T-Bar dropped ceilings, install an air/vapor barrier above the T-Bar system on the warm side of the insulation. Completely seal all edges and overlaps.
• If roof rafter insulation is used, seal the marriage line at the roof rafter joint with approved sealant such as silicon caulk or foam.  Make sure there is adequate ventilation between the insulation and the roof.
• Conduct an audit of older portables scheduled for disposal to determine if retrofitting would be more cost effective than purchasing a new unit.  
• Install occupancy sensors to control the ventilation system.
• Specify that new portables contain windows on opposing walls.
• Specify that new portable units contain exhaust fans on the opposite side of the classroom from the fresh air supply.

  School Partnerships:           

Figure 64.  Energy efficient portable classroom at Pinewood Elementary School in Marysville, Washington.

• Washington Schools - Pinewood Elementary:  An 895 ft² portable classroom (P5) was sited at the Pinewood Elementary School in Marysville Washington in August 2000. This unit exceeded current Washington State Energy Code standards with upgraded insulation in the floor, roof and walls, low-E windows, and a sensor-driven ventilation system that detects volatile organic compounds (VOCs).  A second portable, built in 1985, and also located at Pinewood Elementary (P2), served as the control unit.  (Please see Figure 64.)

  Energy use comparisons of the two classrooms show that the energy efficient portable used considerably more energy than the control portable.  This was attributable to several factors:

  • Incorrect wiring of the exhaust fan, causing it to run continually.  The fan was rewired in 2000 during the summer break.  Once corrected, energy use in the portable declined.
  • Incorrect programmable thermostat settings which were not programmed to turn the heating and cooling system off during holidays and vacations.  Though energy use was reduced when the portable was unoccupied, use was still excessive (Please see Figure 65).
  • Higher air leakage in the energy efficient portable than the control portable.  Blower door testing found 19 ACH at 50 Pa in the energy efficient classroom compared to nine ACH at 50 Pa in the control classroom.  Follow-up blower door, smoke stick, and APT pressure tests indicated that the predominant leakage path tracked through the T-bar ceiling and into the vented attic.  The leakage was a result of an ineffective air leakage barrier in the energy efficient portable.  The control portable contains taped ceiling drywall. 
  • No initial HVAC commissioning by either the HVAC supplier or the school district.
  • Significant HVAC system alterations (including rewiring, ventilation system VOC sensor replacement with a CO₂ sensor, and modifications to other aspects of the HVAC control system) during 2001 by maintenance staff and the HVAC supplier, unbeknownst to BAIHP staff.  Calibration testing done by scientists at the Florida Solar Energy Center on the CO₂ sensors showed significant drift in output results.  This made data collected virtually unusable.
  • The use of plugin electric heaters during the winter of 2001 by the resident teacher because of room comfort problems.  This led to significant room temperature variations and monitoring data showed high plug-load energy use.
  • Poor fresh air flow design with the fresh air intake and exhaust fan positioned so they create a "short circuit" of fresh air, bypassing the students and teacher.

Figure 65.  Graph comparing heating system use of the Pinewood control portable (P2) with the energy efficient portable (P5). Note the energy efficient portable's high energy use during the Christmas holidays due to incorrectly configured heating system controls.

BAIHP staff proposed the following recommendations to Pinewood Elementary:

• Well-defined commissioning protocols, documentation, and coordination among all personnel that service and install the HVAC equipment.  This is a critical component of efficient and healthy classroom operation and should include outside airflow rate measurements to assess adequate ventilation and control testing to insure correct system operation.
• Design changes to the portable classroom manufacturer, including the use of a structural insulated panel system (SIPS), tighter ceiling barrier and sheetrock ceilings, elimination of the vented attic, and relocation of the exhaust fan to the wall opposite the supply air vent. 
• Removal of current HVAC controls and replacement with both an occupancy sensor-driven control for the ventilation system and a heating system programmable thermostat.  Staff also proposed a classroom on/off switch to simplify the system turnoff during unoccupied summer and school vacations.
• Location of exhaust fans in future portables on the wall opposite the supply air vent.
• Window installation on opposing sides of the classroom to increase daylight penetration and to assist in passive cross-ventilation.

Based on the above recommendations, WSU researchers worked with Marysville school facility manager and customer representatives from Snohomish Public Utility District to assist them in setting new construction specifications for 13 portable classrooms they will procure during the next reporting period.  Marysville School District will specify a completely sealed ceiling barrier, a new model heating/ventilation system, a 365 day programmable thermostat, window placement on opposite sides of the classroom, and exhaust fan placement on an opposite wall from the fresh air supply.

• Washington Schools - North Thurston School District:  BAIHP staff also worked with the North Thurston School District to troubleshoot a portable classroom in Lacey, Washington. (Please see Figure 66.)  The classroom was experiencing high energy use and poor indoor air quality.  BAIHP staff tested the classroom, made recommendations including opening the supply dampers, installing a wall side vent to better ventilate the classroom and discussed the specification development process with district staff. The North Thurston School District now is including most of the measures listed in the new procurement guidelines for their future portable classroom purchases. The school district will investigate the feasibility of installing an air/vapor above the T-bar dropped ceiling and will record costs for making these improvements.

Figure 66.  Ventilation system testing at North Thurston School District.	Figure 67.  Weather monitoring system installation in the Boise portable classroom.

• Boise School District Retrofit:  BAIHP staff located a portable classroom at the West Boise Junior High School in the Boise Idaho School District, occupied by a teacher who was interested in having the classroom monitored and retrofitted.  The teacher also is an Idaho State legislator active in education issues, which staff believe will increase the chances of implementing the final recommendations. (Please see Figure 67.)

  BAIHP staff performed a baseline audit, and installed monitoring equipment to track the classroom's energy use during 2000.  In 2001, the classroom was retrofitted with an efficient HVAC system (controlled by CO₂ sensors), lighting, and envelope measures. The classroom was then reaudited, and monitored for the remainder of the year.

  BAIHP staff worked with Pacific Northwest National Laboratories (PNNL) on the pre- and post-retrofit audits, and installation of the monitoring equipment.  In their capacity of providing energy management services to the school district, the local utility Avista Corporation, collected lighting and occupancy data. 

  Monitoring data indicates a 58% reduction in energy usage post-retrofit.  Blower door tests indicate a reduction in air leakage from nine ACH at 50 Pa to five ACH at 50 Pa.   Data also revealed that heating use actually increased on weekends and holidays because of lack of internal heat gain and because the HVAC control systems are not programmed to shut off on weekends and holidays.  The total retrofit cost was $9,892.

  Monitored data suggests that the CO₂ sensor that controls the HVAC system is not correctly configured.  The system does seem to react to an increase in CO₂ levels early in the day, but does not remain on; CO₂ levels only begin to significantly dissipate after one o'clock PM.  BAIHP staff have noted the difficulty of correctly configuring these sensors in other monitored classrooms.

• Oregon Schools:  Oregon BAIHP staff worked with the Portland Public School District to procure two energy efficient classrooms.  These were constructed to BAIHP staff specifications and included increased insulation, high efficiency windows, transom windows for increased daylighting, a high efficiency heat pump, and efficient lighting.  Staff videotaped the construction of one classroom.

  Monitoring equipment was installed by PNNL staff.  Estimates using the software Energy-10 indicated a total energy consumption of 9200 kWh, or $583 per year at Portland energy rates.  Measured results showed the Oregon portable used about 6600 kWh for the monitored period.

  Incremental costs for the energy efficiency measures were $6,705 over Oregon commercial code, including approximately $2,500 for the HVAC system.  This suggests a simple payback of 10 to12 years.

  Initial blower door tests found air leakage rates of 11.3 ACH at 50 Pa.  BAIHP staff also identified significant leakage through the T-bar dropped ceiling and up through the ridge vents.  Other monitoring results indicated that the same HVAC control problems exist with the Oregon classroom as with the others studied in this project.

  The Energy Efficient model outperformed code level models in the Portland area.  The older the classroom, the more energy consumed.  Even when compared with new code level models from the same year, the Energy Efficient model used 35% less energy. Conventional code level classrooms do not include energy efficient measures which greatly increases the unit's operating costs.  Classrooms built more than 10 years ago, use twice as much energy as the efficient model.  Those older than 20 years consume more than three times the amount of energy.  From this study, researches determined that high performance classrooms can save anywhere from $200 to $1000 dollars a year in energy costs compared to older, less efficient portables.

  A survey sent to teachers and maintenance staff indicates a high degree of satisfaction with the efficient portables; the teachers were most impressed with the improved indoor air quality and increased light levels due to the daylighting windows.

Historical Data Collection:  In Idaho, Oregon, and Washington, BAIHP staff worked with local utilities and school districts to obtain historic energy use data on portable classrooms.  This data will be used to compare energy usage from the energy efficient portables monitored in this study.

In Idaho, BAIHP staff worked with Avista Corporation's energy manager to collect historic data on 14 portable classrooms in the Boise School District.  The classrooms each were equipped with discrete energy meters; as a result, BAIHP staff was able to obtain energy usage data for the past three to four years.  A procedure was developed to collect information on portables at each school in cooperation with the physical facilities manager and each school lead.  Historic data collection continues.  Site visits and walk-through audits are planned for these 14 buildings.

WSU will continue to coordinate with PNNL and FSEC on instrumented data collection on the portable classrooms being monitored in Boise, Idaho, Marysville, Washington, and in Portland, Oregon. WSU will work with Idaho to potentially procure and test one prototype classroom with SIPS.  Evaluate and analyze the collected data and prepare articles for presentation and publications.