Temperature and Humidity Sensors

Adding inexpensive sensors to all rooms, is the first step in enabling a much more responsive and efficient heating system.

Thermostatic valves on radiators are okay, but they never seem to work as well as one would hope. Radiators in ‘cool’ rooms (toilets/hall) getting red hot whilst radiators in ‘warm’ rooms (lounge/snug) getting starved of heat. Having the thermostat connected to the thing providing the heat is always going to be a compromise.

Inexpensive, simple battery powered temperature sensors that connect using zigbee or zwave devices are available that can be slowly added to key rooms as required.

Having historical temperature data for all the rooms in the house, will help to identify rooms that are cooling down or warming up too quickly. So even with a manual heating system will allow me to make improvements. For example replacing a radiators or rebalancing the system. Identifying rooms that are loosing too much heat through drafts or voids in the insulation.


Two obvious candidates are very low power battery based devices that periodically transmit the temperature and humidity, using Zigbee or similar low power RF. Or 5V powered WiFi devices, e.g. based on the ESP8266 or similar plus a sensor board.

Off the Shelf ZigBee Sensor

  • Does not need programming, works out of the box
  • Cable free, can be placed anywhere in the room
  • Inexpensive (£10 per sensor)
  • Batteries will run down (every 3 months?)
  • Low update rate means slow to react to local changes, fine for monitoring
  • Needs a gateway to connect to the Home Server
  • Short range, might need two or more gateways

Self Built WiFI Device

  • Long Range
  • Connects to existing WiFi network
  • Very responsive, can send updates on change rather than (just) periodically
  • Mains powered so no batteries to exhaust
  • Flexible, can repurpose the ESP to do other tasks
  • Requires flashing
  • Is Wired, need to be near a socket
  • Ugly cables
  • Inexpensive (£10 per sensor)
  • Needs a power brick / 5v


To start with get both types of sensor, to evaluate the range and battery life of the ZigBee sensors. The ESP based device is a useful development platform for other smart bits and bobs so worth building a development kit and environment.

Initially only get one of each, and use them to do week long surveys of each room in the house to see what the warming/cooling profile is like.

Assuming build up a whole house network, will need around 13 sensors:

  • Lounge * 2
  • Kitchen
  • Study
  • Bed 1
  • Bed 2
  • Bed 3
  • Bed 4
  • Top Room
  • Henry’s Den
  • Ensuite
  • Bathroom
  • Outdoors

Rooms / Areas that are not monitored:

  • Porch
  • Hall
  • Downstairs Loo
  • Landing
  • Utility Room

Although unlikely to need to control the temperature in the bathrooms (these are ‘always on’ rooms) in the future may want to monitor humidity and control the ventilation level.

If using Zigbee sensors then also need to add a gateway device, assuming I add a Zigbee gateway to the Home Server