Smart ventilation – let’s have fresh air in the house at all times

All in all, if you live in a smart home, you shouldn’t just focus on comfort functions. You should also be concerned with life quality and air quality.

This topic is only partly connected to smart homes, as the air quality within the home is pretty much determined by the materials used for insulation and by the equipment operating in the home.

We used to live in a traditional house, categorised for energy efficiency as A/B. We had plastic doors and windows. Airing the rooms was a daily task all the time, because the brick walls didn’t provide adequate air circulation, and the plastic windows hermetically sealed the rooms. When the rooms were aired, the CO2 content went down and you could feel the stuffy air being replaced with fresh air. The main disadvantage of this constant window-opening practice was the temperature fluctuation. In the winter, this meant higher heating bills; in the summer, overly warm rooms.
Then we moved to the smart home I’ve been describing on this blog. This house has a continuously running ventilation machinery to always provide fresh air in the rooms. The chart below shows you the advantages of the system.

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You can tell when we moved to the new house; that’s when the relatively high and continuously changing CO2 level switched to a constant and low value. The physiological effect of this is that you no longer breath in stuffy, smelly air – whether sleeping at night or going about your business during the day, you have FRESH air. Let me describe the process without going into too much detail:

  • air keeps coming in from the outside
  • air keeps going out from the inside (the two must be balanced)
  • going through a heat exchanger, the heat of the air inside warms up/cools down the air coming in
  • the air is filtered through with 2-3 air filters. These must be replaced every 6-9 months (this costs 50-75 USD a year)

This sounds great but… sometimes what sounds good in theory, may not work well in practice. We have the misfortune of living in an area where people use solid fuel-fired boilers. So on windless days in the winter smoke settles on the street. It’s particularly bad when your neighbor uses a fireplace from the 1800s to burn every piece of trash he finds, and he has a chimney no taller than 4 m to let the smoke out. So, one day, after the wonderful ventilation system let all the smoke inside the house, we came up with a solution: we decided to add active carbon filters to better filter the air in the heating period. Unfortunately, on those days when the weather was really windless and the neighbor burnt really stinky stuff, not even this solution worked. Even though it looked like it could withstand a chemical attack… So we finally realised that the only thing we could do is to set a timer for the ventilation system, which until then worked continuously. Now we turn it off between 4 pm and 10 pm. This was the time period when the smoke was particularly unbearable. Of course this is only needed when the external temperature goes below 15 degree Celsius.

Why am I saying this? I just wanted to warn you guys that while the fresh air effect of the ventilation system is great, you always must pay attention to every factor. If you want to use something more sophisticated than your senses to measure the air quality, you’ll need smart gadgets.

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I’ve grown to like the Netatmo product family because

  • it has a clear and informative interface


  • its rain forecast is based on local air pressure data, so to me it seems more precise than anything I’ve tried
  • if you want to monitor more than one locations, you can easily do so on your phone (e.g. your vacation home)
  • it measures CO2 data
  • it stores historical data, so if you need to look something up for some reason, the data are there at your disposal
  • it checks sound volume, so it can act as a burglar alarm
  • it can be connected to external services. For help with this, check out

All in all, if you live in a smart home, you shouldn’t just focus on comfort functions. You should also be concerned with life quality and air quality.

Introduction – or what makes a home smart

How can this practical guide help you?

I’d like to begin by saying that this blog does not approach the concept of intelligent homes from a technical perspective. I’d like to offer you a little help by showing you how functional descriptions should be taken into consideration so that what you get at the end, is NOT a haunted house but a home that works in accordance with your wishes.

The things described in this blog should be used to ensure that

  • the contractor does not take you for a fool
  • the contractor can see whether the system to be introduced is suitable for the job
  • the contractor can decide whether he/she can fulfill your requirements
  • you do not pay two-three times as much as planned for the system programming
  • you will not tear your hair out a few months after the system is set up, and your significant other will not move out saying the smart home is more irritating than helpful


Just like for any other job, appropriate tools are necessary for setting up a smart home. In our case, these tools are the sensors. Without sensors, the home is not really smart, as processes and events are usually tied to changes. You can think of sensors as ingredients for cooking. If you only realise retrospectively how it should have been done, your dish may turn out inedible and you may need to start from scratch.

Sensors/inputs not linked to particular rooms:

  • light sensor(s): their job is to tell you the intensity of light measured in lux. For houses, north-facing light sensors are recommended to control lighting, and south-facing ones to control shading. North-facing sensors in the shade give you a steady light intensity reading, while the south-facing ones can trigger the shades should the sun come out unexpectedly. If you use south-facing sensors to control lighting, even the last rays of sun may be detected by the sensors as bright enough to keep the house unlit. For apartments, semi-detached and attached buildings, the outdoor sensor should be installed wherever it gets the most sunlight.
  • wind sensor: if a sudden storm hits, the wind sensor prevents the window from breaking by lowering the shades. It also prevents the sunshade from being torn off the wall.
  • power outage sensor: (can be a simple magnetic switch) the home’s smart features only operate with power. For this reason, an uninterruptible power supply (UPS) is strongly recommended to bridge power failures. If the UPS is used for more than emergencies (for example for emergency lighting), a signal must tell it which light is to be turned on during a power failure and which isn’t.
  • precipitation sensor: to control sprinklers/irrigation systems

Sensors/inputs to be used in every room:

  • presence sensors: they differ from motion sensors in that they detect smaller movements such as breathing. Before buying, always test their operation in a quiet space, because they emit a clicking noise due to their relays continually switching on. The types with lower noise levels are more expensive… If possible, their sensitivity should also be tested (do they really detect breathing or do they need to be waved at? and what is their range?).
  • temperature sensor: can be used to control heating but may also come in handy as a fire alarm (it’s strange for a room to have temperatures over 30 degrees Celsius). In order to control the shades, outdoor temperature sensors should also be used. After all, if the weather’s cold but the sun is shining, you can save some energy you would use for heating.
  • water sensor: pipe bursts can cause significant damage; a water sensor can shut off the main valve immediately upon detecting a water leak. But you should inform your cleaning staff about the sensor, because mopping the floors with plenty of water may falsely trigger the system.
  • door and window sensors: despite what you may think, these are not only good for intruder detection. For example, it’s good if the system can tell from the open patio door that you’re on the patio, and the automatic shades do not lock you out when you’re working on your tan.

Coming up next: avoiding hidden problems; things to know about networks; switches…