anyone here far north with a walpini or a pit greenhouse?

Is anyone here in the far north that has tried out a walpini / pit- greenhouse and would like to share their experience? I have been scouring the internet without any luck. I'm located in Iceland, latitude 64°. Here the summers are cool and winters are mild. Summer averages around 10°C and winter averages between 1 - 2°C. I'm mainly thinking of using the walpini/pit-greenhouse to extend the growing season and use the thermal mass to keep the greenhouse warm during the night. This would not be a used for a year round production since that would require grow lights.

I realize my climate is a bit unusual, being this far north without extreme frost.

Hi herdis; I am surprised to hear your temps that far north ! Have you looked into rocket mass heaters ? We have built one in our greenhouse and absolutely love it. The ability to burn any small dry wood at 95% efficiency and store that heat for hours is revolutionary ! We simply replaced 15' raised bed with a rocket stove and mass, instead of planting into this area we now use it to set trays of starts on keeping them and us toasty warm. There is a forum here at permies all about them.

Hi Thomas, thank you for the reply
the reason for the temperate climate is because we get the warm gulf stream that warms up the island during winter but also cools the summers.

If I were to use external heating I would use the runoff water from our house. We use hot geothermal water to heat up the house and currently we have plumping under the pavement next to our house and use the warm runoff water from the heating system to keep the pavement snow and ice free during winter (sounds crazy I know!). It could easily be extended to were I want to build the greenhouse.

But I'm also interested in passive ways to keep the greenhouse warm during the cold spring/summer/fall nights.

I would think that the only limiting factor for you with that temp range would be winter sunlight. However, with the correct amount and type of glazing material, you might be able to successfully use water for simulating a tropical type environment. The walpini design will eliminate a risk of frost in your climate and the summer daytime temp could reach over 30* with regularity. Water storage would even this out a bit but maintain evening heat. With such high winter temps, I'm not sure I'd bother with sand mass or other such long term heat storage. It'd be a lot of trouble for minimal gain.

Also, totally envious of your climate.

Hello Herdis! I live in north Norway (70 degrees north) and am very interested in getting made a pit greenhouse. We also have the Gulf Stream, but probably have greater variations of temperature than you have. We also have 2 months of "Polar night" (twilight) with corresponding midnight sun for 2 months... But even though we can't grow during winter, we can greatly extend our growing season by having a pit greenhouse. We have even been thinking of the possibility of putting up a little windmill to power extra heat if needed...
I also find it very difficult to find useable information for us living in a bit "extreme" conditions... Hope this forum can help us...