There are plenty of differences between closed cell foam and open cell foam. Where would you use it, where wouldn't, you, and the big question Will either of these soak up water? Open cell foam typically has a much lower R value when compared to closed cell which is much higher. The open cell also is much less dense in comparison, which is why many builders will often use closed cell foam because it actually adds to the structural integrity of the home in terms of strength. Matt Risinger tests the waterproof qualities of each foam, and he finds that closed cell foam is shockingly absorbent and open cell is definitely not. Even with high amounts of liquid. Closed cell is basically the Lexus of foams," pricy but high quality for a reason. Watch the full video and get the inside scoop about foams.