I am currently planning a house build and looking into the best integration strategy for my smart home. I am a complete newbie to this, so please bear with me!
To be honest, I would ideally love to go with a full KNX setup. However, I’ve quickly realized that a complete, native KNX implementation is incredibly cost-intensive. To keep my budget under control, I’m looking for clever ways to save money without sacrificing too much functionality.
I had an idea regarding the motorized blinds (shutter/blind control). Instead of using expensive KNX actuators for every single blind, what if I wire them conventionally to the power supply and control them via a cheaper smart hub (like a Somfy gateway or a similar Home Assistant-compatible bridge)?
My main question is: Is it possible to use a MDT Glass Switch II Smart (connected to the KNX bus) to control these non-KNX blinds? Ideally, I want to press a button on the MDT switch, have that signal pass through the KNX-to-Home Assistant gateway, and then let Home Assistant trigger the automation to raise or lower the blinds via the third-party hub.
Has anyone implemented a similar hybrid setup? How reliable is the response time when routing a KNX switch press through Home Assistant to a non-KNX device?
What other smart tips do you have for saving costs in a KNX environment by leveraging Home Assistant? I really want to avoid buying a dedicated KNX actuator channel for absolutely everything.
I can relate to that feeling. I did a full on renovation with KNX and am living in it for about 2 years.
After diving into the KNX world really deep (got certified and everything because I wanted to) I can tell you they are numerous ways on saving money without compromising functionality.
I would recommend calculating your solution with the blinds because usually that is one of the cheapest options with the actuator since it enables you to use the cheap 50€ motors for each roller shutter. Every smart motor will very easy cost more than that plus the partial of the relay.
If you do have a lot of dimmable lights DALI might be worth a look. Yes the gateway to KNX is expensive but the controllers on the actual lights is cheaper. Depending on your setup that could scale.
It is possible to control non KNX devices through HA with the Glass Switch. The correct function here is expose. However you will loose one of the main benefits if KNX: resiliency. If your network or your HA goes down your blinds might lock up. That is especially relevant in the case of a fire. Also think about resale value. A half finished system that relies on one specific software might lower the value.
Generally for KNX I can tell you it’s best to mix and match what you want. Don’t just blindly trust one manufacturer. Also get KNX to all the corners you might need it. It’s way better to have the cable there and not need it than otherwise.
If you are looking for cheap and great switches. Look at Lingg&Janke. In my opinion they have a really nice click for a really good price. Also consider some of the offerings from Zennio. They have nice displays and REG modules that can cover small apartments if your house has an extra one of those.
Usually the bigger the relay the cheaper it is per channel. If you calculate that through with the likes of Shelly and others there is most of the time an edge for the KNX solution.
Also consider a smart smoke detector. These can usually be wired together with a fire cable and then only one needs the KNX module. That can save some money too.
All in all I’m really happy with the KNX system I built and looking back I would probably have put the green cable in a few more places. The robustness of the system is really outstanding. There hasn’t been a time when something didn’t work right away. The integration with HA is top notch and the costs were really worth it in my opinion. If you have any further questions feel free to send me a dm
That's pretty much unnoticeable from the Knx-HA-side. If the receiving integration has internal delays (cloud maybe) that would need to be accounted for.
Adding to Richards post, a cover actuator channel is about 35€ in Knx (ABB, MDT, etc.) and supports simpler (cheaper? I don't know) motors. That comes with some advantages and tradeoffs:
easy to replace - even in a decade or two... On both sides - the motor and the actuator
doesn't need batteries
can be operated independently of smarthome software from your wall switches
doesn't have perfect status - knx actuators use time based position calculations. These may or may not be perfectly accurate (but is perfectly fine in most installations)
doesn't provide support for fancy functionality like soft-open, soft-close, multi speed
Invest time in planning. Build what you need, but still lay conduit everywhere you think you could need it at some point.
In knx a common thing seems to be to have switchable sockets. I can't recommend that - it needs lots of actuator channels and isn't flexible. You don't want to change actuator parameters / group addresses after moving a floor lamp. Running switched lines next to powered once over a long distance may lead to unwanted effects (eg. cheap decoration leds glimmering when turned off). Power measuring channels are quite expensive in Knx.
Test the switches. I've just been to a hotel that uses exactly the switches you want to buy. Wasn't really impressed by display quality and reliability / speed of touch-detection and the lack of haptic feedback (aesthetics aside).
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