Case Study: University Reduces Dorm Energy by 45% with PIR Sensors

Overview

A large state university with 10 dormitories (3,000 student rooms) was facing rising energy costs and sustainability goals. Dormitories consumed 8 million kWh annually at a cost of $800,000. Students frequently left lights and electronics on when leaving for class.

The Challenge

The university faced several specific issues:

• Students left lights on when going to class
• Common areas (lounges, laundry rooms) were lit 24/7
• Bathrooms had lights on continuously
• HVAC ran regardless of room occupancy
• Energy waste contradicted university sustainability goals

The Solution

The university implemented a comprehensive PIR occupancy system:

• Sensors: Leviton OSSMT ceiling-mount (common areas) + Lutron Maestro switches (bathrooms)
• Student rooms: Key card + PIR occupancy sensors
• Integration: Building management system for HVAC control
• Quantity: 3,000 student rooms × 1 sensor + 500 common area sensors = 3,500 total

System logic:

• Student rooms: PIR + key card = occupied (HVAC normal). PIR only = unoccupied for 30 minutes (HVAC setback)
• Bathrooms: Occupancy sensors with 15-minute hold time for lights, 30 minutes for exhaust fans
• Lounges: Occupancy sensors with 30-minute hold time
• Laundry rooms: Occupancy sensors with 15-minute hold time
• Hallways: Occupancy sensors with 10-minute hold time, dim to 20% when unoccupied

Implementation

The rollout was completed over one summer break:

1. Weeks 1-2: Dormitories 1-3 (900 rooms, 150 common areas)
2. Weeks 3-4: Dormitories 4-6 (900 rooms, 150 common areas)
3. Weeks 5-6: Dormitories 7-10 (1,200 rooms, 200 common areas)
4. Week 7: Testing and commissioning

Total project cost: $350,000 (sensors, installation, integration). A $100,000 utility rebate reduced net cost to $250,000.

Results

After the first full academic year:

4,000,000

2,200,000

45%

2,000,000

800,000

60%

1,000,000

400,000

60%

1,000,000

500,000

50%

8,000,000

3,900,000

51%

$800,000

$390,000

$410,000

表

Additional benefits included:

• Reduced CO2 emissions by 2,000 metric tons
• Improved sustainability rating (STARS Gold)
• Student education on energy conservation
• Reduced maintenance calls (burned-out bulbs)
• Eligibility for green building certification

Key Lessons Learned

1. Key card integration improved accuracy: PIR-only missed students sleeping late.
2. Bathroom exhaust fan delay prevents mold: 30-minute hold time after motion stopped.
3. Student communication was essential: Explaining the system reduced complaints.
4. Hallway dimming saved significant energy: 20% light level while unoccupied saved 80% energy.
5. Summer installation minimized disruption: No classes during installation.

Conclusion

This case study demonstrates that PIR occupancy sensors can deliver 45% energy savings in university dormitories. The $410,000 annual savings and 7-month payback period (after rebate) made this a highly successful investment. The key to success was key card integration for student rooms and hallway dimming.