Room Climate and Ventilation Monitor

[requiemmg]

Hi,

for your inspiration, this is my new little project for room climate surveillance:

What it does

It monitors Temperature, relative and absolute humidity inside and outside.
It also tells me (symbols in the bottom line) if I should open or close the windows, which is especially useful as I use active cooling without dehumidifying with my heatpump in the summer. In the worst case, this might lead to condensation if I get below the dew point (though the heatpump has mechanisms to prevent this) or to increased mold risk.

What components where used?

Waveshare 2.13 Inch e-Paper Cloud module - this module comes with ESP32 onboard and also includes a 2000 mAh battery pack.

Humidity and Temperature Sensors - you need one outside and one in every room that is to be monitored. I used the Aqara Zigbee H&T modules which are also visible in the picture

Housing for the ePaper with battery was 3D printed from This Thingiverse design

I rotate absolute and relative humidity once per minute. Also, I switch between more than 2 rooms on a floor every 2 minutes (I have one of these devices on every floor) as the screen is relatively small and I like it to be clearly readable. I use a counter sensor and change screen content depending on its value.

For the calculation of absolute humidity I use the Thermal Comfort plugin.

To calculate the need of venting a room, I have an automation firing every 15 minutes, which checks
a) if relative humidty is below 60% (then everything is ok)
b) if it is above 60%, I check the difference between absolute humidity inside and outside. Currently, I use a threshold of >3.5 g/m3 to indicate the need for opening a window and <0 to close the window (might apply in the summer when cooling the house). These values might to be adjusted.

If anyone is interested I can share the code of ESP32/sensors/automations.

[requiemmg]

Now I made an addition to prevent condensation and mold forming.

The problem:
We have a heat pump which can also cool the house during hot summers.
But: Outside it is hot and humid, so when the doors/windows are opened, hot air which is rich with water comes in. Worst case: Temperature below the wooden floor is cooled below the dew point and condensation will occur, thus leading to damage of the floor and mold growth.
The heat pump actually does have a dew point sensor and will keep a safety distance of 5°C above that dew point. But it is only one sensor which is located on the top floor - where it is relatively warm (roof, movement of hot air to the top level…).
In the other rooms, especially in the cellar (which is not a storage space but living and sleeping rooms in our house) temperature and relative humidty may greatly differ.

The solution:
I added hardware and automations to shut down the circulation of cold water room specific.

1. A shelly 1Plus PM with shelly addon and temperature sensor to determine the temperature of my heat pumps cold water output (if you have a newer one, you might get this value directly from a heat pump integration or modbus or KNX or…)

2. Several Shelly 1 Mini’s. These were connected between the (activating) room thermostats and the NC valves which open or close cold water circulation for the room.

3. Aqara H&T sensors for each room - they were present anyway in most rooms for the above solution (which is also extremely helpful in the summer to show when it is useful to open or close the doors and windows).

In Home Assistant:
I utilize the Thermal Comfort plugin anyway to calculate absolute humity. This plugin also calculates the dew point. I created sensors for each room to calculate the difference between the Current cold water circulation temperature and the dew point.

      - name: "Temperature difference sample room"
        unique_id: "temperature_difference_sampleroom"
        unit_of_measurement: '°C'
        state: "{{ states('sensor.outgoing_temperature_from_heatpump')|float - states('sensor.sample_room_dewpoint)|float|round(2) }}"

And then just created an automation which triggers every 15 minutes and switches the shelly1 minis on when everything is ok or off when the difference between cold water and dewpoint is lower than 4°C.

This of course also works when you use air condition or dehumidifiers, as the dew point calculation includes the relative and absolute humidity.

[Fallingaway24 (Justin)]

Cool, you got temperatures displayed on the wall. Seems really useful to have.