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Occupancy Sensors vs. Events2HVAC

Occupancy sensors work well for lights, but not so well for HVAC controls. Let's compare using occupancy sensors for HVAC controls to using Events2HVAC.

Occupancy sensors are reactive. Occupancy sensors cannot predict when an event will occur and get the space ready before the event begins. They can only react when someone arrives for the event. HVAC can require 20 minutes to 2 hours to make a space comfortable, depending on the size of the space and other variables. People attending the event will be uncomfortable for some time and may complain to facility managers.

This is the #1 reason why occupancy sensors should not be used to control HVAC in scheduled spaces – and why building planners should not be putting them in construction specifications for HVAC in classroom buildings, event spaces, and conference rooms.

In addition to people being uncomfortable at the start of an event, occupancy sensors also keep HVAC running unnecessarily and waste energy. Here are some situational examples of reactive occupancy sensors wasting energy:

  • Occupancy sensors typically run HVAC at occupied settings for 20 minutes or so after everyone has left an event. If someone comes back for a jacket left behind, or enters momentarily for some other reason, you can add another 20 minutes of runtime.

  • If a student enters an empty 300-seat auditorium and sits down to study between classes, an occupancy sensor will sense it and begin heating/cooling the entire auditorium. Of course, this applies to smaller spaces too.

  • As janitors move through classrooms, hallways, and other spaces performing their duties, occupancy sensors will trigger HVAC – potentially even at night. While this makes sense for lighting, you might not want to run HVAC for 20 minutes if a janitor walks through a room.

Events2HVAC is proactive. Events2HVAC includes pre-start times for each zone or piece of equipment, so rooms are always comfortable when events begin. It will return equipment to unoccupied settings promptly at the end of each event – unless you add a post-stop time, positive or negative, to extend occupied time or cut it short and “coast” through the end of the event to save more energy.

Because Events2HVAC sends commands based on room schedules, unscheduled events such as a student sitting down to study in a large auditorium, a janitor walking through an empty room, or someone returning for an item left behind after an event, will not trigger HVAC equipment.

Occupancy sensors decrease control instead of increasing it. Occupancy sensors hand over control of HVAC systems to building users. Their actions now determine which spaces are running as occupied and for how long. The average building user is not going to think much about their impact. Most of them probably won’t even realize they have an impact.

Events2HVAC keeps control in the facility manager’s hands. It’s a proactive way to automate HVAC scheduling and eliminate heating and cooling empty rooms. This software integrates room schedules to HVAC controls. It is compatible with more than 20 different room-scheduling systems including Ad Astra, CollegeNet R25 and 25Live, EMS, Microsoft Exchange and Outlook 365, G Suite (Google Calendar), ShelbyNext, SimpleChurch, and more. (See Event Providers.) It can send commands to most modern building automation systems, as well as some WiFi thermostats and security systems. (See Device Interfaces.)

Facility managers maintain ultimate control when Events2HVAC is in use because they can override commands in the building automation system when necessary. If a command is missed for any reason (controller offline, etc.), Events2HVAC will send an email alert to the facility manager so they can correct the problem. Facility managers can even automate demand response with Events2HVAC. (See Automating Demand Response with Events2HVAC.

Zones of control are very flexible with Events2HVAC. For example, you can connect a VAV that serves a foyer or hallway to all the rooms nearby so that any time at least one of those rooms is scheduled for use, the VAV in the foyer or hallway will also be set to occupied. There are also options for triggering only on the first event of the day and the last event of the day, which is useful for exterior door locks or older air handlers that you don’t want to cycle on and off during the day.

Events2HVAC is less expensive and less intrusive than occupancy sensors, and much easier to maintain over the long term. Because Events2HVAC is a software solution, there is no hardware to purchase, mount, or wire. Therefore, labor costs related to implementing and maintaining Events2HVAC are much lower than labor costs to implement and maintain occupancy sensors – especially on a large campus. At most sites, Events2HVAC is installed on a virtual machine on an existing server. There is no interruption of activities in classrooms or other spaces due to Events2HVAC implementation or maintenance.

Email to request a proposal or schedule an online demo of Events2HVAC.


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