To Orchard B, that design with the bricks sounds very interesting, would love to see a diagram if you ever stumble across a picture? I love to study the old designs, it seems to me often enough that we left behind some great innovations in the past.
To CG100, I think 5' would be ideal here as well, but high groundwater where I'm at makes that an impossibility, fortunately enough we never get that cold here and from some studies I read from Oregon State University the soil remains fairly stable here once you get below 3'. One of the best studies I read, reported that as shallow as 12" had a temperature lag of 3 months behind the current. As mentioned above most of the American research into these ground source air geo thermal is done in the Midwest where they talk of depths of 6-9' to get below frost lines and into stable temps.
It's an experiment for sure, hope to get the greenhouse up in the next couple of months and we will monitor over the next few years to see how it does.
Mark
To CG100, I think 5' would be ideal here as well, but high groundwater where I'm at makes that an impossibility, fortunately enough we never get that cold here and from some studies I read from Oregon State University the soil remains fairly stable here once you get below 3'. One of the best studies I read, reported that as shallow as 12" had a temperature lag of 3 months behind the current. As mentioned above most of the American research into these ground source air geo thermal is done in the Midwest where they talk of depths of 6-9' to get below frost lines and into stable temps.
It's an experiment for sure, hope to get the greenhouse up in the next couple of months and we will monitor over the next few years to see how it does.
Mark