WATER is obviously a cheap blowing agent but has limitations for both foam processing and final foam properties.
Foam density is substantially higher and good adhesion and foam surface quality are more difficult to achieve.
Water blown foams also have a higher thermal conductivity. Waterblown foams, which are not protected by diffusion
tight facings, are subject to a gradual increase of thermal conductivity over time, much more than is the case for
foams produced using a physical blowing agent.