Originally Posted by gbstewart
. . . . Question... would it be worth replacing the fiberglass insulation with stryofoam?
I say, yes. Go to a home show and look at the demonstrations of air currents through fiberglass insulation. Get some condensation into it, and in cold weather fiberglass turns into a block of ice with no R value (ask me how I know). Heating and cooling of the space will create a vacuum that will draw either cold outside air or moist inside air through any possible opening.
You've done the hard part already, exposing the old insulation. But only you know what your budget, your intended use, and your climate would be. If I was cash-strapped, and I had to decide between foam insulation or wall material, I would have bare foam first. But then I live where it is occasionally below zero° (F), so as always, your mileage may vary.