Building a Cob Wine Cellar made sense to me since the thermic quality of the Cob is fairly good.
But, of course, a series of conditions are necessary to maintain cool indoor temperatures.
The roof must have a double layer so that air can circulate in between and sweep away the heat from the sun.
The best way to achieve that was to have a double arched roof with a 2 feet wide space, so that a large amont of air can go through.
Another advantage of building arches was to use small (scrap like) 2 feet long studs-glued and screwed together- which cost me about 40 cents each.
Another condition to keep temperatures low inside the Wine Cellar was to avoid any sunrays on the wall, which can be easily achieved with plants and trees.
Finally, correctly oriented doors that can be left open during the night can have a sweeping effect and certainly cool off the cob wall.
It is indeed extremely rare for nightime temperature to rise above 70degrees F.
Here comes another difficulty...
How to firmly attatch an arched structure to a COB wall?
I welded 4 inch long screws to a 3 feet long reebar, 120 times, to have one vertical screw pointing out from the finished Cob wall at one foot intervals.
To be sure the screw will never come out, I welded a horizontal reebar in the center of the wall, then added 3 feet of Cob wall on top.
Now I was able to screw the plank as a platform where the arches will be nailed down.
My 2 young helpers worked for me 3 days a week, and were a big help to put together 15 identical arches made of over one thousand pieces of wood.
But what a satisfaction when the first arch stood up.
The entire construction is curved around a virtual center with aproximately a 40 feet radius. It was challenging to build such precise cob walls to allow for the arches to align.
I guess I have been very lucky.