Plywood sheathing before foamboard as per structural code. 1" of XPS (R-5) will warm your sheathing and prevent condensation there, up to 56%RH at 70* in the room. With just 1/4" (R-1.6), you are safe only to 48%RH. Local EPS may be rated at only R-3.5 per inch thickness, but I would get rid of the insects around the house first, as they love foamboard. If using ESP, install the housewrap exterior of it to control water intake/storage. If XPS, install housewrap first, tape the vertical joints in foam, and get the window/door flashing correct. http://www.buildingscience.com/docum...ting-sheathing
At annual low temp at 47*--- http://www.average-temperature.com/temps/MO/St%20Louis
your sheathing temp is at 49* with only R-1.6 f.b. or 52* with R-5.
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!