#notewindows NY PERC
The Florida Solar Energy Center Logo
Home > Research > Buildings > Energy Efficient Schools > PERC > NY PERC

Stylized Text: Energy Efficient Schools: PERC.

Picture of NY PERC.New York Performance Enhancement Relocatable Classrooms
Cornwall, New York

The NY PERC built by Design Space Modular, in McCrae, Georgia are (2) end-to-end 24’-0” x 36’-0” classrooms sharing a common wall, corridor and bathroom, totaling 1,724 sq. feet (click here for a view of floor plan 1 and here for floor plan 2). During testing, each classroom was occupied. The PERC's were located next to the conventional built relocatable classrooms and was expected to be 50% more energy efficient and have enhanced lighting levels.

Click here for: More Detailed Performance Data

Measured data shows that an overall savings of 36% were achieved for the combined heating and cooling loads. Good data collection periods were November 17, 2002 – June 20, 2003:

Picture of Info Monitor Logo.
FSEC monitored energy performance in both classrooms. All data was downloaded daily to FSEC via modem. Data summaries can be accessed online at the InfoMonitors web site. Detailed data queries and graphs can also be generated through FSEC's WebGet database.
Picture of Weather Logo.

Construction efficiency related differences between the two NY classrooms are listed in the table below. The results of testing are described below.

NASEO Side-by-Side Study of NY PERC: Specifications of Standard and Energy Efficient Construction
Characteristic Standard Relocatable PERC
Floor Insulation R-11 R-13 Formaldehyde Free
Wall Insulation R-11 R-19 Formaldehyde Free insulation w/ ½" jpolystyrene board
Ceiling Insulation R-19 R-30 @ roof deck, w/ airspace between rafters for maintaining cold roof (see details)
Note of caution
Windows Season Shield 
Double Glazed
Low-E Thermopane by Atrium
(U= 0.24, SHGC - 0.38)
Lights 3,072 Total Installed Wattage 1,536 Total Installed Wattage
Skylights None 12 SunOptics skylights
Interior Floor Finish 26 oz. rolled carpet Non-permeable backing, Interface carpet tile, low VOC glue
Heating System Bard Electric Resistance Heat Bard QTec Heat Pump, HSPF 7.5
Cooling System Bard Central Air Conditioning
Bard Qtec Central Heat Pump
Ventilation System Fixed CFM during occupancy CO2 control for ventilation with 3-step fan speed and energy recovery ventilator (click here for more information regarding this ventilation control mechanism)Bard CS200 Energy Monitor 
Bathroom Exhaust Fan Broan, 4 sone Broan Ultra Silent Fan, 1.0 sone
HVAC through Wall Install
Standard gasket provided with unit-rough opening not addressed
On site - sealed rough opening at HVAC wall connection with mastic and fiber tape
Image 1 | Image 2
Duct Joints Industry Standard Sealed with Mastic (post construction)
Building Leakage* CFM25out = 3627 CFM25out = 3692
Building Leakage*
ACH50 = 16.37 ACH50 = 16.66

*Leakage Testing performed – December 9, 2002

Lessons Learned - Improvements Proposed for Next Construction
Characteristic Comment
Light Operation PERC lighting controls at the NY PERC were never commissioned to operate automatically, therefore savings would depend on the operators. The control classroom had the option of only using half the lights and data shows that the teachers in the control classrooms turned lights off when the classrooms were unoccupied. However the teachers in the PERC did not turn out the lights when the classrooms were unoccupied.
Skylight well The skylight wells were fabricated on site. Due to the confined space that relocatable classrooms have in the attic plenums, this was difficult to completely contain the natural illuminance within a site retrofitted well construction commission.
Skylight installation on site vs. in factory Due to time constraints, the weatherization commission of the skylights was not fulfilled. The skylight apertures were flashed with the EPDM roofing membrane at the factory but temporarily covered with plywood sheathing during transportation. During the time it took for the unit to be delivered the sheathing was exposed to the weather causing the EPDM to sweat and swell. When the sheathing was removed for skylight installation, the flashing had adhered to the sheathing. Steps were not taken to properly re-flash around the skylight curb.
Skylight selection Using Solatubes (FL PERC) in lieu of Sunoptics
Roof deck ventilation detail The PERC classroom specified insulation at the roof deck (see note of caution). However the manufacturer substituted a baffle system called Permavent, which is designed for use in site built construction. Future strategy of roof deck insulation should include a spray foam insulation product like Icynene, which is applied at the roof deck at the factory.
Influencing control During the design/specification process of the experimental classroom, FSEC submitted changes to the manufacturer/leasing agent for review/approval. This influenced and motivated the leasing agent to upgrade elements in the control classroom. It was difficult to convince the leasing agent to encourage the use of lower performing materials.
Time Due to the nature of modular manufacturing schedules, classrooms are typically built in 5 days.  This does not allow room for change orders that may require lead times and often substitutions are made that are disadvantageous to the integrity of the project.
Wall insulation Adding ½” polyisocyanurate, to mediate factory oversight of increas3ed wall insulation, created another problem of door jamb size discrepancy. If time would have permitted, wider door jambs could have been installed. Instead, the insulation was “routed” out around the jambs to make fit.
Control over punch list A punch list is a list of discrepancies that need to be corrected by the contractor/builder. Once the modular classrooms have left the factory, the delivery company are then responsible for mating or finishing the classrooms. However, once the classrooms are delivered, the school then retains ownership and is responsible for acquiring a certificate of occupancy. Getting the appropriate party to finish/commission items that were required or necessary to “punch out” on site was difficult and often completed by FSEC.


The premise for this project derives from past research conducted by FSEC and others. Click on these links to be directed to these published reports. http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1272-01/index.htm and http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-951-97/index.htm. As mentioned, there have been several other groups and organizations who have also researched and measured the benefits of enhanced systems and construction practices in relocatable classrooms, i.e. higher efficient HVAC systems, better electric lighting and controls, the use of vapor barriers, etc. The PERC project goes one step further and incorporates the latest research conducted by Heschong Mahone Group on the effects of day lighting in classrooms. Their report confirms and documents that children in more naturally lit classrooms perform 20% better than those in less lit classrooms. Also, 40% of the children tested, were taught in relocatable classrooms. This report can be viewed in depth on their website at http://h-m-g.com within the link titled: “Daylighting & Productivity Study”.

Optimizing the skylight to floor ratio was simulated to determine the size, layout and quantity of skylights that would optimize light levels in the classrooms. A program developed by HMG, SkyCalc was utilized using various supplemental electrical lighting scenarios. The simulated results of using 6 skylights in NY climate with 3 step electrical lighting operation are shown below:

Graph of Total Energy Cost Savings from Skylights.

As mentioned in Lessons Learned, the PERC lighting controls were never commissioned to operate automatically therefore savings would depend on the operators. The control classroom has the option of only using half the lights and data shows that the teachers in the control classrooms turned lights off when the classrooms were unoccupied and teachers in the PERC did not.

Picture of a Classroom.   Picture of a Classroom.
Control unit with electric lighting off
Experimental unit with electric lighting off

Measured Energy Savings

The graph below shows the average shape of the energy savings over the entire school year over a 24 hour cycle from November 2002 - June 20th of 2003.

Graph of Total Electric Energy Demand Profile.

The measured overall energy savings of the more energy efficient experimental model was 48 kWh/day or 36%. Most of the savings were concentrated in the evening and early morning hours when the heating season was operating at its maximum. Note that the average peak electrical demand of the experimental unit at 8 AM is more than 2 kW (20%) lower than the control.

Click here for: More Detailed Performance Data

To see construction status, future data collection, and specifications for other PERC's, please visit the links below.

Picture of FL PERC.
Picture of NC PERC.


FSEC would like to especially thank the industry partners who have donated time and equipment in this worthwhile project. 

ATEX Distributing John Michael john.michael@atexac.com 352-787-0002
Camroden Associates Terry Brennan terry@camroden.com 315-336-7955
Chapel Hill High School Jeff Thomas   919-929-2106
Design Space Inc. Roy Farmer Roy@designspaceinc.com 912-384-9211
Ellison Windows (Atrium) Chris Reilly   800-732-6543
Heschong Mahone Group Lisa Heschong lheschong@h-m-g.com 916-962-7001
Icynene Gabe Farkas gfarkas@icynene.com 888-946-7325
Interface Flooring Liz Rozelle liz.rozzelle@us.interfaceinc.com 877-428-0328
Johns Manville Carlos Bolivar   305-205-6702
NASEO Frank Bishop fb@naseo.org 703-299-8800 
North Carolina Solar Center Kurt Creamer kurt_creamer@ncsu.edu 919-515-4092
Orange County Public Schools Doug Goddard Goddard@ocps.k12.fl.us 407-317-3700
Rebuild America - Energy Smarts Schools Larry Schoff lschoff@rev.net 540-961-2184
Resun Leasing Brian Gromlich bgromlich@resunleasing.com 407-240-6767
Roger Carter Corporation Currie Smith   252-523-7077
SensorSwitch Inc. Maurice Oliver moliver@sensorswitch.com 800-727-7483
Solatube Bob Westfall bwestfall@solatube.com 760-597-4406
South East Modular Jim Ginas JGinas@SoutheastModular.com 352-728-2930
Sun Optics Jim Blomberg highnoon@sunoptics.com 800-289-4700
Williams Scottsman Mike Sico msico@willscott.com 973-589-1234

Project Lead:
Danny Parker
Principal Research Scientist
(321) 638-1404


Note of Caution: Roof
Construction details were provided to the modular manufacturer specifying how an airspace for ice damming prevention. However, the manufacturer substituted “perma vent” baffles, which are typically used in site built construction, in lieu of specified thermoply. This would have been an acceptable substitution if the rafters were spaced as specified at 24” on center. This would have ensure that the baffles were fastened properly to the roof sheathing.. This spacing was also overlooked which mandated the trusses to be cut and framed for the skylight well clearances.

Note: Windows
The original specification that FSEC worked from to improve the relocatable classrooms specified “aluminum framed, double glazed glass, vertical slide windows”. FSEC improved this specification for the PERC by specifying “vinyl framed, low-e argon filled insulated glass with U=0.35 or less.” However, the windows for the control classroom were upgraded upon construction to Season Shield vinyl framed, insulated Low-e glass. Furthermore, there will not be any performance differences between these two windows within the envelope due to this change order to the control classroom.

Ventilation Control Mechanism
In lieu of the typical HVAC wall hung unit ventilating the classroom as per ASHRAE Standard 62-1989, which requires that the space be ventilated at a rate of 15cfm per person, the PERC classroom used a CO2 control to ventilate the classroom on demand in accordance with the CO2 levels in the classroom. The typical HVAC units are equipped with a fan that when air conditioning or heat is not being called for, then the unit is ventilating at one speed in order to meet the demands posed by the ASHRAE standard. The PERC has a multiple speed fan that only ventilates at the rate needed in accordance with the parameters as follows:

  • High fan speed to run when CO2 levels in the classroom are 1100 ppm or more
  • Medium fan speed to run when CO2 levels in the classroom are at 750ppm –1100ppm
  • Low fan speed to run when CO2 levels in the classroom are between 450ppm and 750ppm
  • Ventilation is off 450 ppm or less