You helped author a new report that finds that commercial buildings could save tens of thousands of dollars on their

Question: You helped author a new report that finds that commercial buildings could save tens of thousands of dollars on their energy bills by adding an occupancy sensor to their ventilation fans. Can you explain how this small change leads to big energy savings?
- Keywords:
  dollars,
  energy,
  sensor
Asked by Aido to Aisling, Colin, Laurence, Ned, Niamh on 28 Feb 2016.
- Ned Dwyer answered on 28 Feb 2016:
  
  I´m by no means an expert on this. However, currently in most buildings, things like lights, heating, ventilation is turned on and off manually, or sometimes linked to a timer. It would make more sense if these systems were able to know if there were people in the building and if they needed to be on. The idea of intelligent buildings is growing and that is what your question relates to. Basically, if the ventillation system only needs to be activated when there are people in the building then there will be a significant energy saving, as the system is not active when the building is empty. Howevver, what happens if it detects a mouse crossing the floor? Maybe he gets well ventilated!!
- Colin Shirran answered on 28 Feb 2016:
  
  The ventilation fans only need to be used whenever anyone is actually in the building. If you had them to just turn on whenever they occupancy sensor detects that someone is there, you will save a lot of energy doing that compared to having the fans on all the time day and night.
- Laurence O'Rourke answered on 3 Mar 2016:
  
  Good question. Ok let’s assume they are working all week 24 hours per day so without an occupancy sensor, the energy used is 168 hours in total.
  
  Now assuming people work 8 hours per day out of 24 hours, then 16 hours per day of “free” energy would be lost if the ventilation fans keep working while they are out of the office. At weekends, you lose 48 hours.
  
  So with a simple occupancy sensor linked to the ventilation fans, you could save a minimum of 128 hours of energy out of 168 hour week. That’s a lot of saving. Sounds like an idea worth spreading Aido.

Question: You helped author a new report that finds that commercial buildings could save tens of thousands of dollars on their energy bills by adding an occupancy sensor to their ventilation fans. Can you explain how this small change leads to big energy savings?

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