Open Cell vs. Closed Cell
When insulating buildings, you have a choice of two different types of spray foams: Open Cell Foam or Closed Cell Foam. In Closed Cell, the cell structure is tighter which increases its density, typically a 12” cube of Closed Cell would weigh 1.7 to 2.0 lbs. The same 12” cube of Open Cell would weigh 0.5 lbs.
Since Closed Cell is tighter, it is better at moisture permeability, vapour permeability, R – Value per inch of thickness and even adds structural strength to the building. Closed Cell expands at a rate of 30 to 1, Open Cell a ratio of 100 to 1.
Although Closed Cell is better, it is also more expensive since the material does not go as far for the same cost. If money is no object, you will want Closed Cell, but if dollars are tight, you will want Open Cell which gives you the best R-value unit per dollar spent.