Portable Classrooms - Indoor Environment

Shingle Creek Elementary School, Orlando, Florida

The FL PERC, located at Shingle Creek Elementary School in Orlando, Florida was sited in September 2003. The entire Shingle Creek Elementary School campus is composed of relocatable classrooms. The Fl PERC was built by Resun Leasing and South East Modular. Dimensionally, it is a 24�-0� x 36�-0� classroom with a bathroom totaling 864 sq. feet. The control classroom was intended to be built by the same manufacturer (South East Modular) but due to scheduling conflicts, it was built by United Modular. The base construction from each manufacturer is nearly identical. Each classroom was occupied during testing. The PERC was located sixteen feet south of the control unit. FSEC monitored energy performance in both classrooms. All data was downloaded daily to FSEC via modem.

Results

Overall Results

Data collected from November 1, 2003 through May 12, 2004 showed that the modified classroom achieved overall energy savings of 65%.

Construction efficiency related differences between the two FL classrooms are listed in the table below.

Side-by-Side Study of FL PERC
Specifications of Standard and Energy Efficient Construction

Characteristic Standard Relocatable PERC
Floor Insulation R-14 unfaced R-14 unfaced Formaldehyde Free
Wall Insulation R-11 faced R-14 unfaced Formaldehyde Free insulation w/ Dens Glas with polyisocyanurate foam insulation board
Exterior Door HM pressed steel knock down CECO with solid core R=2.44 HM pressed steel knock down CECO with polystyrene core R=14.8
Ceiling Insulation R-19 faced R-30 Icynene spray foam insulation @ roof deck
Roof Standard dark roof; 0.45 mm black EPDM over Densdeck Reflective roof; 0.45 mm white EPDM over 5/8" Densdeck
Windows 1/8� non-tempered bronze tint glass (U-1.03, SHGC=0.84, Vt=0.77) Low-E Argon gas filled vinyl framed by Ellison with Solarban 60 glass (U=0.28, SHGC=0.39, Vt=0.71)
Lights 1,420 Total Installed Wattage 984 Total Installed Wattage
Outdoor Light 60 Watt incandescent Manually controlled 15 Watt CPL., photosensor controlled
Skylights None (7) 21� diameter Solatube Skylights
Interior Floor Finish 26 oz. Rolled carpeting Non-permeable backing, Interface �Sabi� carpet tile, low VOC glue
Heating System Bard Electric Resistance Heat 10kW heat strip, 35900 BTU heat Bard Qtec Heat Pump HSPF 7.5
Cooling System Bard Central Air Conditioning 3.5 ton with ERV 43000 BTU cool SEER 10 Bard Qtec Central Heat Pump With ERV SEER 12
Ventilation System Fixed CFM during occupancy CO2 control for ventilation with 3-step fan speed and energy recovery ventilator
Bathroom Exhaust Fan Broan, 4 sonne, 100 CFM Panasonic Whisperlite Fane, 1.3 sonne, 190 CFM
Duct Leakage* CFM25 total return=318
CFM25 total supply=485
CFM25 out return=253
CFM25 out supply=426
CFM25 total return=325
CFM25 total supply=420
CFM25 out return=216
CFM25 out supply=274
Building Leakage* ACH50 = 2673
ACH50=4850 (ACT removed)
ACH50 = 1107
ACH50-1139 (ACT removed)
Smoke test Infiltration air handler unit on  2.60 ach
Infiltration air unit off  0.27 ach
Infiltration air handler unit on � 0.66 ach
Infiltration air handler unit off � 0.05 ach
*Leakage Testing performed � December 9, 2003

Detailed Results

The graph below shows the predicted annual energy savings potential for typical modular classrooms in various climates. The 46% energy savings predicted for the FL PERC was substantially surpassed with actual savings measured at 65%.

The timing of the savings are shown in the average daily load profiles shown in the plot below.

Lessons Learned

  • Use R14 insulation in lieu of R15 because R15 is only manufactured in 14� widths and 96� lengths, as opposed to R14 which comes in rolls and 16� widths, which is more suitable for 16� on center construction, i.e. wall cavity)
  • Providing timely and easily understandable information to teachers and maintenance staff is a must.
  • Use of the Solatube which included a tube that is standard with the skylight well required no extra fabrication for the skylight well area.
  • In hot, cooling dominated climates such as Florida, measures that reduce lighting and its internal heat generation show greatest promise to reduce building energy needs.
  • Daylighting is particularly attractive in this location although solar control glass is important to reduce the space cooling liability. Similarly, light colored surfaces and solar control glazing looks more important than insulation.
  • Heating system type is not as critical as cooling efficiency.
  • Floor insulation is counterproductive.