Replacing 74-year-old roof

Thanks. Obviously, there is much I do not know about the construction and ventilation of your home. However, as a general rule, I never recommend metal roofs on residences without solid decking. The absence of solid decking makes it very easy for condensation to occur. I also suspect that your home does not have a vapor barrier behind the ceilings and walls, further increasing the likelihood of moisture ending up in the attic and condensing on the underside of the cold metal roof. So, why has this not been a problem in the past? Well, there could be several reasons. One may be that your home is not very airtight and moisture is driving out of it in other ways. However, if you do something like house wrap or insulation on the walls or new siding or new windows and doors, then suddenly everything gets a lot tighter and at that point, condensation will occur in the attic. And, in fact, your new roof may by itself be "tighter" than the old one. So, is decking the "answer"? No, but it helps. If there is any way to increase ventilation (both intake and exhaust) in your attic when the new roof is installed, that would be very helpful as well.