I recently learned of a builder in climate zone 6 who uses a wood foundation. When I first heard about it, I assumed that it was a new technique. Apparently it has been done for a long time and they've got several houses standing for many years.

It's an intriguing idea. They say that since wood is more of an insulator than a conductor, it also creates a more habitable sub grade environment (a better finished basement).

Has anyone heard of this? What do you think?

this is periodically discussed here in depth - some like them, but no one has explained why anyone would want to install a 50 year (or even a 100 yr) foundation under a building that could stand for much longer than that. Sure, it's cheaper, but it's short term thinking.

And this is how round XX starts........

I would highly recommend that the OP search for the topic in existing threads here on GBT. That should entertain them for a while.....