Blown insulation is commonly used in the construction industry for insulating building walls, floors and attics. Insulating materials such as fiberglass, rock wool and cellulose fibers are pneumatically blown into open cavities in the building structure to provide thermal insulation. A number of systems have been devised for pneumatically conveying insulation materials for this purpose. Blown insulation is limited in its application to closed cavities or horizontal surfaces because there is nothing other than gravity to hold the insulation in place.
A more recent variation on the blown insulation process is sprayed insulation. Water or an adhesive is added to the insulation material as it is blown into the wall cavity to make it adhere to vertical or overhanging surfaces. With this process, insulation can be quickly and efficiently applied to the framed walls of a newly constructed or renovated building before the wallboard is nailed in place. When the insulation is sprayed into the open wall cavity, it fills in between the wall studs. To make sure that the wall cavity is completely filled, the spray insulation installer typically oversprays the insulation so that it builds up a half inch or an inch beyond the plane of the wallboard. Then, the excess is smoothed off even with the studs using a motorized shaver. This excess insulation is considered process waste and is usually gathered up and disposed of. This wasted insulation material can sometimes account for up to 20% of the insulation used. Careful control of the spraying process can cut down on the overspray to reduce the amount of waste, but this does not come without a price. The increased labor cost of slowing down the spraying process for more control can outweigh the cost of the material saved, and the delay slows down the whole construction project.
Certain spray insulation installers have taken measures to combat the inefficient use of material by gathering up the waste insulation and reintroducing it into the spraying process. This is typically done by shoveling up the insulation shavings with a snow shovel and putting them directly into the main feed hopper or an auxiliary feed hopper of the spraying machine. This process has a number of drawbacks. First, it requires additional labor to gather up the shavings and feed them back into the hopper. Second, the wet lumps of recycled insulation can disrupt material flow in the spraying system. Third, the amount of recycled material added to the virgin insulation is sporadic and inconsistent which can compromise the quality and consistency of the insulation application.