Happy to share. My wife and I live in Woodbury, MN which is a suburb of St. Paul. This is USDA Hardiness Zone 4b (2012). After being inspired by a presentation at the State Fair back in 2013 we got into straw bale gardening for a number of years and were intruiged at the possibility of purchasing or building a greenhouse to extend our growing season. It was around then that we learned of the Deep Winter Greenhouse project through the Univ. of Minn. extension, and the various types of passive heating greenhouses that are available. You may have read about the DWG project, but if not there are several of these greenhouses in MN (mostly outside the twin cities) that allow you to grow through the entire winter season. That is a tall order here because of lack of extreme cold and short daylight hours.
Our project started in the summer of last year, was on hiatus through the MN winter, and re-started just a couple of weeks ago. We ended up going with a "home grown" customized geodesic dome design that integrated three different concepts: the Growing Spaces Dome (which we frankly couldn't afford), the Ceres GAHT (geothermal) system, and Paul Robinson's $40 geodome plan, which was scaled to a 16' diameter dome. Ceres gave me a discount on their plan and customized it for a dome. Like the Univ. of Minn. DWG concept, we opted for opaque walls on the N side and insulated everywhere we could. I've attached some photos and captions below to show how we got to where we are now.