EPS or polyiso? Layered, taped seams?
I have found a supplier for EPS (plain EPS, no coatings) or Polyiso (foil faced on one side, white non-reflective on the other side)
1.) The polyiso is double the price. However, it is effectively better at insulating to my knowledge. I assume it should be my pick?
2.) I don’t want to use more than 2″ of foam on the exterior. With either product, I believe it will be advantageous to layer two 1″ thick pieces with staggered joints. If I don’t have the time I will simply buy the 2″ thick and call that good.
3.) Should I tape, caulk, or spray foam the joints of either product? I was reading that all foam shrinks and the tape will do no good after a few years, more so on the EPS since tape doesn’t stick as well to foam particles compared to a foil facing. I also was reading that it is good to leave the gaps uncovered so any moisture can escape. Manufacture of the Polyiso seems to suggest taping joints. The EPS has no instruction.
4.) I plan on using Jeld-Wen or Anderson windows. They will be double or triple paned with Argon. I do not have money to buy the best windows available. Should I build a plywood box with an extra 2″ extension for these windows, or just use longer screws to go through the foam and into the jack stud? I was wondering if the plywood box had many benefits since I am only planning 2″ rather than 6 or 8″ of foam.
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