Which is better, closed or open cell?

Both systems offer significant advantages over fiberglass batting: ability to air seal; ability to fill cracks and conform to odd shaped cavities; and ability to hold their shape over time and under adverse conditions. But closed-cell foam has the greatest thermal insulation value (R-value). Only one-half the thickness required for fiber insulations. In addition, closed-cell foam products increases the strength of you wall system (it’s approximately doubled) and increase the water resistance of your home’s exterior.