Though this is a little OT--thought I'd chime in here for those of you building/remodeling steel frame garages--
1. Look into using overhead "radiant heat" rather than forced air/gas unless your electrical consumer costs are extremely high(read outrageous). I installed this type of a system in my Dad's and his partners business shop, a 70x40x20 steel frame building, when I contracted to remodel and upgrade about 15 or so years ago--radiant heat warms "things" people, equipment, water lines, etc. not the ambient air--warmed air rises leaving floor areas cold demanding more heat--though it costs for the initial install In my Dad's case they paid for the system in their savings on gas heating prices in I think 2 1/2 yrs.
I've also installed this type of system in several custom built homes garages--it can be 10deg below zero out side and initially feel cold inside until you've been in the "heat for a few minutes" then you'll be down to shirtsleeves.
2. If you are working w/a electrical contractor make sure you specify you want as much 220/277low cost hi-intensity lighting you can get and picture your shop and mark on your plans where you want outlets, both inside and out side--how many times have you wished you could plug in a drill in your driveway with a 10-20 ft cord rather than have to run out a 50-100ft cord? Run as much 220 as possible and make sure your breaker boxes are oversized to allow for expansion of electrical needs.
3. Consider adding exterior windows--most quality windows on the market today have great heat retention values with the added benefit of allowing "natural light"-- this helps in many ways especially with employees--many do not enjoy working in a "tomb" like building, kind of nice to look outside to see if it is sunny, rainy, or snowing again
Just a few thoughts from a builder.
Congratulations on your new business enterprises!!!
Milner--have a "qualified" roofer "familiar" with metal buildings inspect your FG roof panels for structural integrity and for signs of leakage(your building inspector should have picked up on this if you had it inspected if it is a used building)--a "qualified" roofer will make the necessary repairs correctly and you can still enjoy the benefit of natural lighting--a real bonus
This a a FWIW