ASHRAE Journal - May 2009 - 32

Characteristic Floor Insulation Wall Insulation Ceiling Insulation Windows Standard Relocatable R-11, Standard R-11, Standard R-19, Standard Season Shield, Double Glazed 14 Fixtures at (4) T12 34 W Lamps Plus 1 Fixture With (2) T12 Each; 15 Ballasts; Other: Bathroom (2) 60 W Incandescent Bulb Plus (4) Outdoor Lights at 60 W; Connected Lighting Load = 2,264 W None 26 oz. Rolled Carpet 10 kW Electric Resistance Heat 3 ton Air Conditioner, SEER 10 Fixed cfm During Occupancy 4 Sone Standard Gasket Provided With Unit. Rough Opening Not Addressed Industry Standard cfm25out = 458 ACH50 = 16.37 PERC R-13 Formaldehyde Free R-19 Formaldehyde Free Insulation With 0.5 in. Polystyrene Board R-30 at Roof Deck, With Airspace Between Rafters for Maintaining Cold Roof* Low-e (U = 0.24, SHGC = 0.38) 12 Fixtures at (3) T8 32 W Lamps Plus 1 Fixture With (2) T8 Each; 25 Ballasts; Other: (2) 15 W CFL for Bathroom, (4) 60 W Outdoor; Connected Light Load = 1,422 W 12 Skylights with Site Modified Skylight Wells Nonpermeable Backing, Interface Carpet Tile, Low VOC Glue Heat Pump, HSPF 7.5 With 10 kW Auxiliary Strip Heat 3 ton Heat Pump, SEER 12 CO2 Control for Ventilation With 3-Step Fan Speed and Energy Recovery Ventilator 1 Sone Sealed Rough Opening at HVAC Wall Connection With Mastic and Fiber Tape (On Site) Sealed With Mastic (On Site) cfm25out = 271 ACH50 = 16.66 Lighting Skylights Interior Floor Finish Heating System Cooling System Ventilation System Bathroom Exhaust Fan HVAC Through Wall Install Duct Joints Duct Leakage Building Leakage * The intended airspace between air barrier and the roof deck was not constructed as specified. The manufacturer made a substitution that was not approved and could not be mediated after the unit was constructed. Table 1: New York standard and PERC specifications. than the control. The slightly greater demand around 4 p.m. is due to a difference in the lighting controls systems. HVAC. All the enhanced portables were equipped with heat pumps, whereas conventional practice in portable classrooms typically uses strip heating. While this incurred an incremental cost (including additional cost for improved SEER), this translated into energy savings, especially in the New York and North Carolina comparisons where heating is a greater part of the annual HVAC loads. Figure 2 shows how the heating, energy savings varied over the winter months. Savings from November to March averaged 79 kWh or 47% even with a problem with the control thermostat in the PERC portable. This occurred when the system did not turn off the HVAC during unoccupied periods and maintained abnormally high temperatures. Other difficulties were experienced with the control of the auxiliary strip heat, which was always activated with the heat pump. Trial and error procedures isolated the problem as a thermostat compatibility issue with the automated control system. This was resolved near the end of the project. Savings likely would have been higher in a second year of monitoring (the units were vacant in 2003–2004). Lighting. Figure 3 shows the lighting demand profile evaluated over the year. Performance was disappointing as the experimental unit had a lower installed connected lighting load, 32 ASHRAE Journal Figure 2: Comparative monthly space conditioning energy, Cornwall, N.Y. as well as the daylighting system, which should have reduced lighting energy use. However, the teacher in the control classroom often turned on only half of their lighting for use with an overhead projector, reducing comparative systems. Also, due to hardware troubles, we never achieved satisfactory daylighting responsive controls in the experimental unit. ashrae.org May 2009

ASHRAE Journal - May 2009

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