Wet-spray cellulose is designed for use in attics or wall cavities that are fully open (prior to the installation of the interior finish material). The sprayed material conforms to any substrate, around pipes, obstructions, and over cracks, reducing air infiltration and forming a highly efficient and effective thermal barrier.
After application, the insulation is planed even with the stud faces by the use of a “stud scrubber” (Fig. 9.2). The scrubber shaves the insulation mass so that it is flush with the face of the studs, thereby creating an insulation “blanket” custom-fit to the wall cavity (Fig. 9.3). The wall can be closed shortly after installation of the insulation; however, vapor retarders, as well as some types of paint and vinyl wallcoverings, should not be applied to the inner surface of the wall until the insulation has dried. Moisture-to-fiber ratios influence the drying time required after application. Although these times may vary with each manufacturer, 24 hours is a consistent average among most products. Moisture control is critical with wet-blown insulation because overly moist insulation requires a longer drying period before a wall can be closed up. It is also recommended by some that vapor retarders of any type should not be used with spray-applied cellulose. This recommendation may conflict with some building codes.