Danero, there was 1 C by celsius in the old greenhouse when outside was -27 C! The old greenhouse has 0,9 m depth. It is difficult to build a such deep tranch.

yes I know but how do you get in , I'm 6.5 feet tall

Also you said that in the old greenhouse you had 1C , the new one have never been tested in guess so in the heat of the summer day what is the ratio outside/inside temp

thank you

This is my citruses inside my new greenhouse.

a lot of them lack some nutrients

but is quite impresive what you got there , congratulations !

waiting for daily report on this winter , temp in/out

This morning we have had the first frost on the ground.
Inside the greenhouse was +9,0 C.

first frost ?!?! now?

well , it is very good temp , I was wondering if having so much light on your citrus , the 9C would cause any WLD?

The frost was on the ground only. The temperature at height above 1 m was +1,7 C. The same temperature was in the Kherson witch is located near Black sea This autumn is very cold.
My citruses have quite well sunlight - the walls have reflectors.

P.S. what is WLD?

winter leaf drop - caused by the sun rays on a cold day when the leaf temp is very high due to the sun and the soil is under 20 C

Last year i have no WLD at all. I have used special material to cover my greenhouse. It sounds "izolon" by russian.

Very impressive! Try putting some metal barrels painted black filled with water to store the heat from the sun during the day, at night they will give the heat back and keep the greenhouse warmer.

I use the plastic bottles with water for accumulation sun heat.

the walls are made from concrete ?

The walls are made from the slate (roof cover).

Here is pic of my suffered (in spring) citrus. It blooms!