With normal insulation technics you will have condensation. The only way to stop it is if you eliminate air movement true the insulation. This is not impossible, depending on the situation. On a commercial metal building, spray urethane or even wet spray cellulose will work. If you situation is a metal roof on a house w/ a rafter ceiling, a continuos vapor barrier & dense pack cellulose will work. These are not technics for the inexperienced. You would need to consult a professional.
The first choice is to vent. The amount of ventilation required is usually specified in builing codes. You still need to prevent air moving through or around the insulation. If that is not stopped, your vents will draw on that first (Point on least resistance).