The beer you produce will be far more consistent throughout the year if the complete sidewall and cone is properly insulated. I know some of the big boys use uninsulated vessels in temperature controlled rooms, but when they are fermenting 2000 hl beer + per vessel, the fermenting beer wort is virtually unaffected by the room temperature - which is held at a constant temperature +/- 0.5 deg C. I have worked with slightly smaller uninsulated FVs and the speed of fermentation and the flavour changed according to time of year, if we had to open door to the outside for CO2 removal etc etc. And another (micro) where they had to go in a temperature controlled room - which cost as much or more to run over the long term, as paying extra for insulation and using in a relatively uncontrolled environment.

Pay a bit extra and get insulated tanks - uninsulated ones are simply not worth it.