So Frank , we have a wrap around porch that is above ground level 3-4 ft (open bottom w/ lattice at openings), which does make it colder . It's technically a screened in summer porch. We do have windows frames enclosing the entire porch for winter. Keeps out the wind but that's about all. I'm sure that without the insulation/tarps/quilts I would have had quite a number of dead trees, as it would have been almost as cold as the outside temps . Years back , there were winter temps that froze things I had stored on the porch.
We first placed a large tarp on the floor, then added rolled insulation(pink rolls) over the entire tarp, then added another tarp on top of that . All the smaller pots were placed on the house wall side. We put insulation between and around them - there were 2 rows. The larger pots were placed next . We didn't put insulation in between/around the larger pots . Although that would be something I would do now.
We hung tarps on the window side to keep the light/cold out. Watered them and I covered all the figs with old quilts , moving quilts , whatever I had .
I don't know what prompted me to do all that but I'm sure glad I did.
Lately the porch has been pretty warm with the warmer outside temps and still enclosed. Tarps are off the windows. So we decided to put them all out today , and of course it's chilly tonight, ugh. Not freezing but 50 and very windy. We just went out and tarped them to protect them from the winds and my young newbies are back in the house.
Negronne and Italian Purple are still questionable. JH Adriatic dead, although a member in NJ says his do fine in his unheated garage! I guess it was something I did , can't figure it out though, since much smaller ones in 1 gal. pots did ok.
Hope this helps.