Insulating a metal shop?

Mine is a 30x46 with double bubble. The biggest drawback with my shop is lack of ventilation, it becomes an oven if the doors are all kept closed. The insulation does a decent job until late afternoon on a 90* day, then it loses the battle. I'll be putting in a gable fan and fresh air vents thru the winter.
That whole spray foam thing scares me! When it catches fire, it goes real quick.