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Johnson Controls GLAS review: Costly Cortana-powered GLAS thermostat has a striking design, but it's not for everyone

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The Good Johnson Controls' GLAS Smart Thermostat has a built-in Cortana speaker and it also works with Alexa and Google Assistant. In addition to its basic capabilities, the GLAS provides indoor and outdoor air quality reports. Its unique, see-through OLED screen surprisingly doesn't get too smudgy-looking after regular use.

The Bad You're paying a premium ($319) for the OLED touchscreen and the integrated Cortana speaker.

The Bottom Line The GLAS is a solid smart thermostat, but it isn't a good value if you don't feel strongly about its transparent display and Cortana functionality.

7.3 Overall
  • Features 8
  • Usability 7
  • Design 7
  • Performance 7

Johnson Controls' GLAS Smart Thermostat costs $319. That's 70 bucks more than the Ecobee4 and Nest Learning Thermostat. Given that, the GLAS had better be pretty spectacular to compete. 

In some respects, it is.

It's immediately clear you're paying extra for the GLAS' neat-looking see-through OLED touchscreen and its built-in Cortana speaker. The Johnson Controls thermostat also monitors the indoor air quality, so you can see, at a glance, if you should circulate your HVAC system's fan. That's a really nice touch. 

The app and the OLED display are responsive and simple to navigate, too, making for a good overall user experience. 

My issue is with its value. You need to really love the see-through touchscreen and its native support for Microsoft's voice AI to feel good about spending $319 on a single smart thermostat. That said, the GLAS is surprisingly versatile -- it works with Alexa and Google Assistant (assuming you have compatible Amazon and Google devices, since those speakers aren't directly integrated into the GLAS like Cortana is). 

If you specifically want support for Cortana and you really like the GLAS' unique aesthetic, you might not mind its comparatively high price. Everyone else should weigh it alongside some of the other great Wi-Fi thermostats we've reviewed.  

The GLAS is only available in the United States. At the current exchange rate, $319 converts to roughly £250 or AU$440.

Getting to know the GLAS

Installing the GLAS is roughly the same as installing any other smart thermostat we've tested -- with one notable exception. Since it's see-through, you'll have to patch more of the wall behind it. 

Any holes from previous thermostats or weird patches with old paint, will definitely show up when you install the GLAS.

To get around this, Johnson Controls includes a large back plate (which we used), but it somewhat defeats the purpose of having a see-through thermostat to begin with. If you're willing to put in the extra time patching and painting, though, the GLAS will look really neat.

The other thing to note is that the GLAS requires a C-wire. Not sure what that is? You can read more about it here, but definitely consult a professional if you have questions or need help with this (or any) installation. 

If your system doesn't currently have a C-wire, Johnson Controls includes a C-wire adapter in the box with your purchase. Still have questions? Visit Johnson Controls' support page where they discuss all things GLAS installation. 

Here are the basic steps:

  • Turn off power to your current thermostat
  • Remove its faceplate and take a picture of your current wiring
  • Disconnect the wires and unscrew (and remove) the old thermostat's baseplate
  • Route the wires through the GLAS' baseplate (or the back plate first, if using)
  • Screw down the baseplate with the included hardware
  • Connect the wires to the correct terminals
  • Attach the faceplate/wire cover and turn power back on to your thermostat

The GLAS should power on immediately and walk you through the setup. It will ask you questions like, "What time do you usually wake up?" and "What's a comfortable range for when you're at home?" to get a sense of your preferences. The GLAS has internal sensors designed to determine if you're home or away automatically, but giving it an idea of your preferred settings helps it balance comfort and energy savings. 

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