Insulate your portable building with traditional batt insulation, astro armour or spray foam!
Traditional Batt Insulation is R -15
Astro Armour is a vapor barrier, radiant heat reflector and it is also an R-15.
1" Closed Cell Spray Foam is also R-15. 
 
You can mix and match what type of insulation you want and where you want it. A common example is Astro Armour in the floors, Spray Foam in the ceiling and Batt insulation in your walls. This is a cost effective combination that will allow your shed to have proper air flow.  Another popular combination is to spray foam the floors and ceiling and use batt insulation in the walls, for the same reason. 
 
Prices are available with the rest of your finishing package on your quote as it varies by size and type