Ventilation System Automation

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  • Post last modified:22/01/2022
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My home has a Heatrae Sadia/Itho HRU ECO 4 fitted. The HRU ECO 4 MVHR (Mechanical Ventilation with Heat Recovery) is a whole house ventilation system.

Ventilation System Automation

The HRU ECO 4 removes contaminated wet air from kitchens & bathrooms and simultaneously provides fresh preheated air to other rooms in the home. I control the HRU ECO 4 using wall mounted switches/dials with low (1), medium (2) or high (3) fan speed settings.

Ventilation System Automation

This project’s focus is ventilation system automation from real-time Humidity and Volatile Organic Compounds (VOCs) data.


Monitor Air Quality

My first objective is to source sensors that collect, process, and visualise Humidity and VOC levels within my home.

With this data, I can set parameters and optimize ventilation within my home.

Automate Ventilation System

My second objective is to automatically turn my ventilation system on for a set duration based on air quality data.

Therefore, removing the need to manually increase the ventilation fan speed using the wall switch/dial and remembering to switch back or turn off after so long which will result in energy savings too.



My research led me to investigate IoT air quality sensors. I found Airthings who produce smart indoor air quality sensors. I bought their House Kit which consists of Airthings Wave, Wave Mini and a Hub.

Airthings House Kit can measure Radon, Chemicals (Total VOCs), Humidity, Temperature and Mould Risk. With an Airthings hub, their sensors support many integrations such as Amazon Alexa, Google Assistant and IFTTT.

Heatrae Sadia/Itho Wireless Control Switch

I read the Heatrae Sadia HRU ECO 4 user manual and I was delighted to discover a Wireless Control Switch was listed in the accessories section. I purchased the wireless switch from

The RF switch is battery powered and offers three settings (low, medium & high speeds) plus a timer (10, 20 & 30 minutes) function.

Ventilation System Automation


Smart Life/Tuya Wi-Fi Relay Switch

I decided to use a Smart Life 4-channel Wi-Fi relay switch to make my Heatrae Sadia wireless control switch “smart.” This Wi-Fi relay supports a momentary mode which will simulate pressing the switch/remote buttons.

Ventilation System Automation

Airthings Wave App

Install the Airthings Wave app on your iOS or Android device.

Apple App DownloadGoogle App Download

The Airthings web dashboard is excellent too.

Ventilation System Automation

Airthings Home Kit Setup

The Airthings Home Kit was super easy to setup. You just need to remove the Wave and Wave Mini back panels and pull the battery tabs to start the pairing process.

Connect power and Ethernet cables to your Hub. Download the Airthings Wave app and follow the on-screen instructions.

Ventilation System Automation

Top Tip Airthings sensors require an initial calibration time of 7 ~days.

Pairing Heatrae Sadia/Itho Wireless Control Switch

To pair a wireless control switch, you must first switch off the ventilation unit, wait for 15 seconds and then switch on the power again.

Within 2 minutes, press two diagonally opposite buttons at the same time on the control switch.

Test the control switch by pressing the high fan speed.

Smart Life/Tuya App

Install the Smart Life app on your iOS or Android device.

Apple App DownloadGoogle App Download

Smart Life Wi-Fi Relay Switch Setup

Connect power to your Wi-Fi relay switch and add it as a new device. From the home screen, press the circular + icon > Electrical > Switch (Wi-Fi).

Ventilation System Automation

Top Tip check your network is set to 2.4Ghz only.

After you have added your Wi-Fi relay as a new device. Name the buttons.

Ventilation System Automation

Tap Setting, ensure Device mode is set to Momentary and Momentary time as 0.5.

Ventilation System Automation

Create Smart Life Tap-to-Run Scenes

Next, you need to create Smart Life Tap-to-Run scenes (for IFTTT) based on your ventilation preferences.

For example, I created a Humidity scene to run the ventilation system at high fan speed for 1 hour and then back to low.

Ventilation System Automation

For VOCs, I created a scene to run the ventilation system at high fan speed for 3 hours and then back to low.

Ventilation System Automation

Soldering Wireless Control Switch to Wi-Fi Relay Switch

This was the tricky bit. Soldering wires to the wireless control switch button contacts. I recommend using colour coded wires for this task.


Please refer to the illustration below.

Ventilation System Automation


Heatrae Sadia/Itho HRU ECO 4 Automation


Before you begin creating custom IFTTT Applets, I recommend linking the Airthings & Smart Life to your IFTTT account by following the similar steps in this tutorial.

Ventilation System Automation

Your trigger will be your Airthings sensor’s Humidity rising to a specific threshold.

Ventilation System Automation

Your action will be initiating the specific Smart Life scenes setup earlier.

Ventilation System Automation

I produced an IFTTT Applet for each of my Airthings sensors around my home.

Ventilation System Automation

Top Tip You can review your Applets activity i.e check if it is working as expected or how many times it has run.

Ventilation System Automation


Wrap Up

I completed the setup of this project in January 2021. Over the past 11 months, it has been working flawlessly.

According to Airthings, VOC contents in the air are low if between 0-250 ppb. Mayo Clinic states ideal indoor Humidity is somewhere between 30-50%.

My En-Suite bathroom has maintained an average of 188 ppb & 47% Humidity.

Ventilation System Automation

My Bathroom has maintained an average of 156 ppb & 45% Humidity.

Ventilation System Automation

My kitchen has maintained an average of 47% Humidity.

Ventilation System Automation

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