Personnel presence detection in residential building without access to location

Hey everyone,
I’ve been a Home Assistant user for a little over 4 years now and I’ve loved it ever since I started using it.
This led me to try to incorporate it at work. I work in a logistics company, and one of our responsibilities is to manage and maintain apartments for companies with personnel that come from abroad.

One problem we are facing is that the residents of the buildings (the personnel) do not care about energy efficiency at all, and always keep the lights and AC on even when they leave the apartment.
I want to solve this problem, and use Home Assistant to turn off the lights/ac whenever no one is in a specific apartment.

We have already acquired the necessary hardware to control the lights and the AC, but we’re still looking into a way to detect occupancy in each apartment in the building.

Some information about the building management:

  • The building has around 20 apartments.
  • All the apartments are connected to the same network but each apartment has a different VLAN/subnet.
  • Home Assistant instance in running on a Synology in the server room of the building and has access to all the apartments’ networks.
  • Each apartment accommodates 3 to 4 personnel at a time.
  • Personnel come in for 2-4 months at a time and are them replaced. The whole time they are on duty, they are allocated the same apartment and room.
  • We do not want to collect location information of the personnel.

Our goal is to find a solution that needs minimal maintenance and is cost effective.

Solutions we came up with:

Solution Effectivness Cost Connectivity Maintenance
PIR sensor 

Will not detect people if they are stationary 

Cheap sensor

Need to put a sensor in each room of each apartment

Wifi: Good

Zigbee: will the sensors be able to communcate only with one hub? or do we need to put a hub in each apartment

Battery powered: need o change batteries every once in a while

Plugged in: Good

MM wave Sensor Very effective, can detect even if stationary

Expensive sensor

Need to put a sensor in each room of each apartment (Can MM wave sensors see through walls?)

same as above

Battery powered: need to change batteries every once in a while

Plugged in: Good

Location based tracking Not an option, we cannot use the personnels location data      
Personal device connected to apartment's Wifi Can track specific person in each apartment None, only using some configuration in router/homeassistant If personal device is off, will not detect occupancy

Need to configure the system with each new personnel's phone's MAC address.

iPhones randomise MAC adresses which makes MAC tracking useless (is that true in the same network?)

Note that I am also trying to minimize hardware purchase. I can very easily buy a mm wave sensor for each room/area in the apartment but that would be very cost ineffective.

So far, tracking the personnel’s personal device in the network seems the best option (if there is no issue with the iPhones), but there’s still the issue of if a phone dies.

Do you think there is a better way of solving this problem? another solution that is more robust/enterprise solution? A combination of solutions?
Plus if you have specific product recommendations that can be integrated into Home Assistant, could help a lot in choosing the best solution.

Thank you Home Assistant Community!

NFC tag reader to enter and exit?
NFC tag could be the same one used at the work premises. Then to disarm the alarm when coming home, tag and it disarm and turns on the lights.
Same for leaving, tag to arm, turning off lights etc.

Yeah just like @seanmccabe says, I was also thinking about a maybe a system similar to the cards used in hotels.

Often you can open your door with this. And after that, inside the room you need to place the card in a slot to make use of the lights and electronics. When people leave, they will take it along with them out of the slot, cause it’s their key.

Multiple PIR sensors
You can also detect the presense based on multiple PIR sensors.

And you can consider setting quite a large time when no movement is set untill presence is set to off.
With the use of Home Assistant you can define automations like when there is 1.5 hour no movement during daytime, set no one home. And if a movement in the evening set someone home until 8.00 am.

There is also the Omron D6T line of thermal sensors. These can also be used to detect persons, even if they are not moving. They do have a maximum area of detection you have to take in account.