I have been dubious about the Nest Thermostat and the Smart Home (see In praise of the Dumb Home); in a properly designed home a smart thermostat is going to be bored stupid. I wrote:
The Nest thermostat turns an air conditioner or furnace on or off, where you might be just as comfortable opening a window or turning on a fan. That's what you would do in a dumb home. Instead, the Nest causes you to use energy to do what used to be free.
I may have spoken too soon. Big Ass Fans has just announced that its lovely Haiku fan can now connect with the Nest thermostat. This is really interesting and important for a number of reasons.
Comfort isn't just a function of temperature; it's a mix of temperature, humidity and air movement, as Victor Olgyay demonstrated so wonderfully fifty years ago. The Nest thermostat can sense temperature, but it can't sense the effect of a fan, which cools your body by increasing evaporation of sweat, a very personal and subjective factor that will vary depending on what you are wearing, humidity and many other personal factors.
The Nest can't actually tell how you feel, but it learns quickly. The air movement makes you feel cooler, and the app then suggests a higher temperature setting for the Nest that takes into account the cooling effect of the fan. The fan and the thermostat know the pattern: you turn on the fan and the Nest turns down the air conditioning. It really is learning the subjective, how you feel, with a cooling device that uses a whole lot less energy than an air conditioner.
According to the press release, each degree you raise your Nest Thermostat saves you up to 5 percent on energy costs. A fan can make you feel quite a few degrees cooler, and Big Ass notes that "If each home thermostat was raised 6 degrees, we would reduce carbon emissions by 78 billion pounds, the equivalent of taking 3.2 million homes off the grid for a year."
Ceiling fans aren't perfect. In fact, the Green Curmudgeon, Carl Seville, claims that Ceiling Fans are Evil-- since they don't actually change the temperature of a room but simply how you feel, if you leave them on when you leave the room they are actually heating the space. I am assuming here that the Nest will know you have left the room and turn the thing off.
I have said in the past that Comfort is a complicated thing that can't really be solved by a smart thermostat. I may have been wrong.
I have been wrong about Big Ass before; in 2006 I wrote Big Ass Fans: Great idea, Dumb Name.