If it fits, put a 33 gallon plastic garbage can over the tree and stick a 7 watt christmas tree bulb in there with it. I would use a dark colored bulb (blue??) to keep the spirit of darkness in with the tree. A small bulb should give just enough heat to keep temps above freezing. Disclaimer: I have never tried this. I just suggested this method to my brother in law who is getting ready to over winter a tree in Minnesota. I, personally, have never tried this. Good luck. FF

FRANK,
I DON'T THINK YOU HAVE THAT MUCH TO WORRY ABOUT
I WOULD SAY SINCE THEY ARE ALREADY PROTECTED
FROM WIND BY THE SHED AND THEY ARE WATER PROOFED
A LAYER OF BURLAP AND SOME OLD BLANKETS OR BETTER
YET RUG SHOULD DO THE TRICK.
IN MY UNHEATED GARAGE ON L.I I USUALLY DONT EVEN RAP
THEM , BUT THOSE OUTSIDE I DO AS I TOLD YOU
WITH THE ADDITION OF A LAYER OF TAR PAPER AND PLASTIC
FOR WATER PROOFING. THIS YEAR I MAY EXPERIMENT
WITH A HEAT MAT PLACED UNDERNEATH. THE THING IS IF
THEY JUMP AHEAD AND BLOOM TO SOON YOU HAVE TO TAKE THEM
BACK IN WITH EVERY REPORT OF FROST.
SO I GUESS GOING OVERBOARD DOESN'T HELP.

MARCANTONIO

Frank,
Is there any kind of insulation in the walls of the shed? That would help to slow the fast temperature fluctuations. Maybe some rigid foam board with a reflective facing could be added. The possibility of using heater tape (like the type used to keep water pipes from freezing) wrapped around the pots to help keep the roots from freezing is also an option, it only comes on near 32F, comes in various lengths and is cheap to power. This is basically what we do to our pump house at the lake cabin. Adding a muffin fan to keep the air circulating lightly will help keep the air from stratifying. Hope this gives you some ideas to work with, I am lucky that I have just enough room in the basement by the garage door for my collection (stays cool and dark most of the winter).
Woody.

Frank, Fig trees can take cold down to twenty degrees without damage. I usually overwinter in an unheated garage and have had the temperature go much lower than that. It seems that the mass of cement in the garage keeps the temperature from falling quickly, and this seems to give the trees time to adjust.
Dormancy is nature's way of protecting these plants. Allowing them to get cold and stay cold helps them go into deep dormancy. Many people on the forum wrap or cover in cold areas without benefit of a permanent structure or heat. There are many posts on the subject on the forum. Doing a search for overwintering will give you a feel for what works in the region.
Some people do heat and simply keep the temperature under 40 degrees. It certainly is an option, and the way to go if you are totally uncomfortable without heat. But by heating your structure you keep the plants in a less dormant state, and more prone to damage if the heating system fails.
If your shed has a good deal of mass (wood, dirt floor, cement, bulky contents,etc.)perhaps a little insulation board on the walls or surrounding the figs would provide enough protection (and peace of mind).

I agree with fignut. I keep a couple of trees in a detached unheated garage in central Jersey. I do cover the trees with leaves and a leaf bag though. I have not had any losses. I find that the trees are fine. But I will say that my yard gets a lot of sun.

Dan Ralph

I have read somewhere in this forum regarding the use of some drums filled with water as insulation or something to that extend. Hope someone with such experiences can or have read the thread can point all of us into that direction.

THANKS ALL ... SOME OF YOU "FIGHEADS" GAVE ME ALTERNATIVES THAT I NEVER EVEN THOUGHT ABOUT.

I'LL LET YOU KNOW HOW THE OVERWINTERING TURNS OUT IN THE COMING SPRING.

THANKS AGAIN FOR ALL THE HELP. FRANK, FROM DA-BRONX