Open cell foam is just what you think it would be. The cells that make up the foam do not completely encapsulate. Meaning the cell are intentionally left open. This causes the material to be softer and more flexible then its closely related alternative closed cell foam.
Since the cells are open this also decrease open cells density. What this mean is that it requires less product to fill areas between studs which in turn saves you money.
One of the biggest benefits of open cell foam is that it expands so much after it has been applied, meaning it can insulate hard to reach nooks and crannies in a home. These types of areas can be hard to insulate with closed cell foam. To explain the differences a little better closed cell foam is designed to expand to about 1″ of thickness when sprayed. With each inch offering an R-value of 7, multiple applications can be applied to achieve higher total R-values. Open cell foam is designed to expand to 3″ of thickness, meaning only one application is possible in most standard walls. These types of areas can be hard to insulate with closed cell foam. Open cell foam is excellent for soundproofing where a single application can completely fill the area between studs.
Open cell foam is also much more affordable than closed cell foam, however this foam won’t insulate a house as well as closed cell foam, so it’s not ideal for locations with extreme weather temperatures