Adopting Vacancy Sensors

Jul 20

Reducing Energy Costs and Complying with Commercial Energy Codes.

What are motion sensor lights? What are vacancy sensors?

A motion sensor light is a light that responds when it detects motion. A kind of motion sensor light is called a vacancy sensor, which turns lights off in unoccupied rooms or spaces. The technology used can vary depending on which company you buy and can use infrared, microwave, ultrasonic or another type of technology. There are two types of occupancy sensors: ultrasonic and infrared. Ultrasonic sensors detect using sound waves, while infrared sensors detect using heat. In the lighting process, occupancy sensors can also be called presence sensors or vacancy sensors.

Why do you need them?

Occupancy sensing controls have an average energy savings of 24% according to IBISWorld report on Building Lighting Control System Manufacturing.

According to ASHRAE/IESNA Standard 90.1-2010, the maximum allowable lighting power density (lpd) for a typical conference room is 1.23 watts per square foot. This means a conference room of size 300 square feet would use about 4 LED light bulbs at 25 watts which would be equivalent to 100 watts for the incandescent light bulb. It would save about 24% on energy. Taking the room to be lit for 12 hours per day, 5 days a week for a year at 10 cents per kiloWatt hour, we would see that it would cost $112.32 meaning that savings would be $26.96 per year.

Classrooms are, more often than not, lit even if not in use. According to a case study by the National Institute of Building Sciences, they found that during 20% of daytime and 17% of nighttime, the lights were left on in an unoccupied room and 46% of students questioned often walk into an unoccupied, fully-illuminated room. Taking the average size of the classroom to be 900 sq. ft. and lpd is 1.24, we assume the classroom has 10 fluorescent tube lights using 15 watts each. For 16 hours a day, 5 days a week at 10 cents per kWh, it would cost $148.99 per year to keep the classroom lit meaning that using a vacancy sensor, the single classroom would save $36 annually.

Additionally, according to Standard 90.1-2010 and any version after, vacancy sensors are required for certain types of rooms including conference, meeting and training rooms. Vacancy Sensors also allow buildings to increase their LEED certification by a point when 75% of the lighting load is connected to occupancy/vacancy sensors.

What are your installation options?

There are two ways of converting your existing switch into an occupancy sensor – rewiring and retrofit.

Rewiring means that you would have your electrician go in and remove the existing switch, cut the wires, reconnect the wires to the new switch along with the other small steps in between. Let’s see how much it would cost as well as payback period. Electricians usually charge from $50 to $100 per hour. It would take about half an hour to rewire a single light switch and so taking the cheapest on the market is about $30, it would cost about $55 - $80 for a single light switch. This means that it would take at least 3 years to get your money back before seeing actual savings.

Retrofit means that an occupancy sensor can be adjusted right on your already installed switch. It means that one wouldn’t have to remove the switch or rewire the wires for putting the new one. InstaHub’s SoLAR product is one such device, which is installed atop the pre-existing switch using the top screw on the light switch faceplate and a commercial grade adhesive in under 2 minutes. Depending on how many you buy, your payback period could be as little as a year!

Why you should choose InstaHub over rewire

As you can see above, rewiring can cost money in installation, technology and still not give you the payback that InstaHub’s occupancy sensor would. InstaHub’s device is the perfect solution for buildings that were made before motion sensors could be added during construction. Additionally, it allows such buildings to increase their LEED certification by a point when 75% of the lighting load is connected to occupancy sensors. It also meets with ASHRAE 90.1’s latest requirements of turning off the lights within 20 minutes after a space is vacated. To learn more about SoLAR - check this page out.