$14/kg for unprocessed V2O5, presumably VO2 is brittle.

Copper, despite all the news stories and it shooting up in 2011 (to almost $10/kg) is today only $5.70/kg pure.

I like the idea of tuning it to act as a passive way to heat and cool homes but compared to fiberglass insulation?

I buy thermoelectric and nonvolatile memory applications though.

One application is a thin window coating, you wouldn't need much of it. The manufacturing process is probably more expensive than the raw material.

This would likely not work well in desert areas over an appreciable period of time, since most vanadium compounds are pretty soft, and desert winds tend to contain very hard particles of silica.

I agree that the window application probably won't work (it's not like it's less thermally conductive than glass anyway), but why wouldn't they just coat the inside of the pane if they're worried about abrasive damage?

Either way, if I were to pick a technology to improve desert glass insulation it'd be with a coating that allows in light but reflects infrared. Windows are mostly radiative heat transport after all, you can always double pane them for more direct conductive insulation.

It's not about thermal conductivity, it's about IR transmissivity. Above a certain temperature it would reduce the IR transmitted to the inside, thus keeping things cooler in the summer while still allowing the inside to be warmed by the sun during winter.

Even in a desert the temperature-dependent behavior may be beneficial to cool during the night. But if it is not then yes, a different, harder coating that always reflects IR would be preferable.