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Occupancy, People, Counting and Energy

The simple act of counting people entering or exiting buildings can provide very valuable data which can be used in a number of different ways. One of thee primary uses is for energy management. At the core of building energy management is an alignment between energy consumption and occupancy of building space. Getting data on energy consumption is fairly easy through the use of meters or utility billings. Obtaining data on accurate occupancy is much more challenging. Aside from retail buildings, very few building owners or facility managers have data on the number of people in their buildings, a time profile of their occupancy, or the count of occupants within the building

The general options for gathering occupancy data are infrared sensors around the door frames, people carrying RFID tags, or access control card swiping, all of which have potential shortcomings.

In a video analytic solution cameras are placed above an entrance or exit that can detect people and their movement in or out of the building. Systems typically collect statistics on space occupancy and variations of occupancy during the day or by day.

One example of the benefits of occupancy and people counts is using actual people counts at the beginning of the workday to startup and ramp up the HVAC system properly. People counting can also be utilized for the ventilation of certain spaces. For example, one of the advanced HVAC control approaches is CO2 demand control ventilation (DCV). Thi is best used in large areas, open office spaces, theaters, assembly areas, and ballrooms. A CO2 sensor is used to optimize outdoor air use along with the energy required to condition the air. The CO2 sensor is really a people counter or at least a metric that helps reflect occupancy. However detecting occupancy through CO2 sensors has its limits, can be unreliable, and provides poor estimates of occupancy. People counting technology with accuracy rates of 95% provides more reliable and accurate estimates of occupancy. Not only can you use the occupancy data to improve energy demand, but, the occupancy data can be used for to evaluate space utilization.

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