Case Study: Smart Office Saves 40% Energy with PIR Occupancy Sensors

Overview

A 50,000 square foot office building in Chicago, Illinois, was struggling with high energy costs from lighting and HVAC systems that operated on fixed schedules. The building was occupied from 8 AM to 6 PM weekdays, but many areas remained empty for hours at a time. The facility manager estimated that 30-40% of lighting energy was wasted lighting unoccupied spaces.

The Challenge

The building had several specific pain points:

• Conference rooms were booked for 2-hour meetings but lights stayed on all day
• Private offices were often empty while employees worked from home
• Open office areas had partial occupancy (some desks empty)
• Hallways and break rooms had unpredictable usage patterns
• The existing thermostat schedule caused complaints about temperature in empty rooms

The Solution

After evaluating several options, the facility manager chose Panasonic PaPIRs+ flat lens occupancy sensors for their high sensitivity and ability to detect seated occupants. Key specifications:

• Model: Panasonic EKMB series with PaPIRs+ technology
• Detection zones: 416 per sensor
• Coverage: 15m diameter at 3m height
• Output: 0-10V dimming for LED lights and BACnet for HVAC
• Quantity: 125 sensors installed

The sensors were integrated with the building’s existing BACnet control system. Lights were configured to turn on automatically when occupancy was detected and dim to 20% after 10 minutes of no motion, then off after 30 minutes. HVAC was set to maintain normal temperature when occupied and setback 5°C when unoccupied for more than 1 hour.

Implementation

The installation was completed over three weekends to minimize disruption:

1. Week 1: Conference rooms and private offices (45 sensors)
2. Week 2: Open office areas (50 sensors)
3. Week 3: Hallways, break rooms, and restrooms (30 sensors)

Each sensor was commissioned with room-specific settings. Conference rooms had 15-minute hold times for lights and 30 minutes for HVAC. Private offices had 10-minute hold times. Open areas used 5-minute hold times for lights near windows (daylight harvesting) and 15 minutes for interior zones.

Results

After 12 months of operation, the results exceeded expectations:

450,000 kWh

270,000 kWh

40%

620,000 kWh

434,000 kWh

30%

1,070,000 kWh

704,000 kWh

34%

$107,000

$70,400

$36,600

表

Additional benefits included:

• Reduced CO2 emissions by 180 metric tons annually
• Improved employee comfort (fewer complaints about cold offices)
• Extended LED light life (fewer operating hours)
• Return on investment achieved in 18 months
• Eligibility for utility energy efficiency rebate ($12,000)

Key Lessons Learned

1. Commissioning is critical: Each room needed different hold times based on usage patterns. Default settings would have caused false-offs in conference rooms.
2. Daylight harvesting works: Perimeter offices near windows saved an additional 15% with light sensors integrated.
3. Employee communication matters: Some employees initially thought lights were malfunctioning; signage explaining the system resolved confusion.
4. HVAC setbacks need longer delays: 30-minute hold times prevented frequent cycling.
5. High-sensitivity sensors are worth the cost: Standard motion sensors would have turned off lights while employees were seated at desks.

Conclusion

This case study demonstrates that high-sensitivity PIR occupancy sensors can deliver significant energy savings in office buildings. The 34% overall energy reduction and 18-month payback period make a compelling business case for similar installations. The key to success was proper sensor selection (416 detection zones for seated occupant detection) and room-specific commissioning.