Thank you Thomas! This is how i want to build it.
Brick casing with field stone as the thermal core and mortar to fill the space between the stones.Wouldn't it better to put even more stone than doing lasagna? Just stone and clay sand mortar?
Basically this time of the year i go to the sea,the weather is still nice here ( 22-25 celsius) and i love how the stones between the sea and the
land , reserve and slowly radiate out the heat from the sun. So much stone here to acquire lot of thermo mass quickly,why would i go for so much cob mixing?
Why do you believe that the ducting will rot out?Also why did you put the straw layer beneath?Do you want to insulare the space beyond and not wanting it to act as a thermomass?Do you want heat faster from the surface?