Extractor fans are typically used in bathrooms, toilets and kitchens to expel damp air and air contaminated by cooking, etc. Whilst not typically considered part of the smart home heating and cooling, they will affect its operation.
When under intelligent control, they can provide a much better user experience and in most cases a zero-touch user experience. They will also work much more efficiently.
As with any smart home sensors, positioning is very important for effective and efficient operation and this is particularly true of humidity sensors. For this reason, we always avoid extractor fans with built in humidity sensors.
If the humidity sensor is not close to the main source of the increased humidity (e.g. a shower) or is not placed at the right level, then there will be a lot of latency in the operation of and extractor fan and it may not even operate at all. If it is too close, then it will run for much longer than necessary.
To measure relative humidity, you need both a good quality humidity sensor and temperature sensor. Many cheaper sensors available are remarkably inaccurate. Our preferred humidity sensor is the Honeywell HIH-4000 series.
Many people think you can simply use a humidity sensor on a bathroom extractor fan with a fixed trigger level to control when the fan operates but, this will be very inefficient and quickly become very annoying. The relative humidity in countries like the UK varies a lot naturally throughout the year, so using a fixed value is going to give very poor results. On warm humid days in the summer the fan may end up running for long periods, whilst doing nothing useful.
A good control algorithm needs to use a 'baseline' and only operate the fan when the humidity rises above this normal level. The baseline could be a value from another sensor in another part of the house or even outside. It may even be a value obtained from an Internet service.
We have found the best way to get a baseline whilst using a single sensor, is use it to also capture a rolling average by taking measurements at regular intervals (e.g. 30 minutes) over a long time period (e.g. 9 hours). This rolling average can then be used as the baseline and will handle changes due to local weather conditions and not be affected by short term events, such as someone taking a shower.
In some situations like our we also use occupancy other sensor information to preemptively control the extractor fan, knowing that the shower is about to be used. This helps reduce the maximum humidity level reached and basically gives the fan a headstart.
The main reasons for fully automating extractor fans are so that they don't turn on just because someone switched on a light. This is especially annoying if someone gets up in the night and the fan is noisy. The fans are also not on a 'dumb' timer, so they only run for as long as needed, saving energy.
They also can't be left on by a person. It is also a zero-touch user experience experience, ensuring best possible user experience and maximum comfort. Our bathrooms are never misted up.
This example tweet from our @smartest_home shows how we have all our bathroom extractor fans under full smart home control, providing a zero-touch user experience.
We are mostly using binary (on/off) extractor fans but we developed a variable speed controller as part of our smart shower controller.
We can associate a controller with any fan to enable intelligent and adaptive control. Fans may also be controlled by a slave processor. Regardless of the intelligent control mechanism, fans can also be controlled by all of the user interfaces in our smart home (assuming permissions allow it) and and this includes buttons.
The actual electronics and electrical wiring can be achieved via numerous methods. We have some low voltage fans and also mains powered extractor fans. We have used Z-Wave modules in the past but we are also using Solid-State Relays (SSR).
Our Home Control System uses models for all the connected appliances and for all types of connected appliances and this includes the various types of fans used in our contextual smart home. Our technology abstraction means that any fan added to our home inherits all of the capabilities. Essentially, every connected fan becomes instantly very smart and they can all be controlled by any of the many user interfaces available, providing a great user experience. Our Home Control System is tracking things like on/run time and off time and can switch extractor fans off automatically if it detects an issue. The fans can also generate voice announcements and notifications if something unexpected occurs.
