Wet-spray Cellulose

While dry cellulose in curtain-truss cavities provides a very attractive system environmentally, there are other—more common—ways of using cellulose insulation in walls. In new construction, the most common is wet-spray installation, in which cellulose is mixed with water and (often) an acrylic binder and sprayed into open wall cavities. To avoid the risk of trapping moisture, the walls should be given a few days to dry out before closing them in, especially if you’re using a poly vapor barrier. Several manufacturers are now developing wet-spray systems that use much less water than the standard 2-3 gallons per 30-lb. bag and can be applied at a lower density.

Wet spray cellulose fills nicely around wires and pipes, and provides a very good air seal. Many manufacturers, in fact, argue that this air seal is sufficient to prevent moisture problems in walls and that poly vapor barriers are unnecessary. Because of the labor and specialized equipment required to apply wet-spray cellulose, a job typically costs slightly more than standard fiberglass batts. The only important consideration to keep in mind when framing walls for wet-spray is to keep corners and pockets at interior wall intersections open, with enough space for a stiff, 3-inch hose to spray straight into them. Future issues of EBN will go into much more detail about the issues surrounding cellulose insulation.