Installation standards and practices
Although this book is not intended to serve as a training manual for wet-spray cellulose installers, the following guidelines will provide a general framework for a better understanding of the application procedures. The guidelines listed below are to be used for general information purposes only and are not intended to supplant or override instructions provided by a specific manufacturer or applicable installation standards. When installing wet-spray cellulose materials, it is essential that the guidelines of the manufacturer are followed, unless superseded by local, state, or federal codes.6
Preliminary inspection and equipment. An inspection of the building should be made prior to installation, with special consideration given to the following areas:
1. All voids around windows and doors should be sealed to stop air infiltration. Various materials such as foam backer rod or urethane spray foam are available for this purpose.
2. All pipes, ducts, conduits, wiring, and outlets should be installed in the wall before the insulation is applied.
3. Any small areas from which the insulation is to be excluded, such as electrical boxes, should be masked.
4. Seal all vertical plumbing and electrical penetrations through both top and bottom plates of all walls.
5. Cover finished areas including windows, doors, fireplaces, etc. It is faster to protect finished surfaces than to clean them later. For this purpose, 2 or 4 mil polyethylene sheeting works well.
6. Cover electrical boxes until the spraying is completed. Duct tape works well.
7. If recycling the wet-spray cellulose, a totally clean floor is absolutely essential before starting to spray. Objects such as nails, wood, wire, etc. could damage the machine. Sweep these from the floor before starting to spray the wet-spray cellulose.
8. Shovels, brooms, and trash cans are usually needed for recycling and cleanup.
Application. Wet-spray cellulose insulation should be applied with the manufacturer-approved spray application machines and spray nozzles. The nozzles are a tube with a liquid atomizing unit attached to intermix fibers and liquid. Nozzles may have from two to six spray tips and must provide a consistent fiber-to-water ratio. A 2V2" semispiral hose, which allows the material to tumble and stay in the air stream, should be used. A diaphragm pump capable of 200 to 300 lb/in2 at a flow rate of 2 to 5 gal/min is used to supply the pressure.
The blower machine may be mounted in a truck or trailer to be positioned at the job site as close to a door as practicable to make recycling easier and increase production. An alternative is to take the machine into the building in a central location. This works very well when spraying in cold weather.
The hose, a minimum of 100 ft in length, should be pulled to the farthest point to be insulated and have as few bends as possible. The water line, run alongside the hose, should be taped to the last 10 or 12 ft of insulation hose for ease of use. After all hoses and nozzles have been connected and properly tested, the installer is ready to begin. It is important to note that specific recommendations from the thermal insulation manufacturer must be followed. Liquid flow tests also should be made periodically to ensure a proper liquid-to – fiber ratio.
When spraying, the installer should aim with a downward spray angle of approximately 5 to 10 degrees and about 4 ft away from the wall. When spraying layers on layers, the cavity becomes one solid mass, with no inner voids, giving it structural integrity. As the nozzle moves from one side to the other, angle the nozzle sideways and maintain 5 to 10 degrees down, spraying into the existing insulation. Nearing the top of the wall, keep the nozzle angled down. To fill the very top, under the plate, turn the nozzle angle up and step in a little closer to pack the insulation against and into the top of the cavity. After the top portion is almost full, step back and level out the nozzle to finish the cavity. Be careful not to overfill the top portion of the wall cavity. The cavities under windows, soffits, etc. must be treated the same as the top plate.
A smooth and steady movement of the nozzle also will help to decrease the amount of overspray (the portion of material from a spray pattern not filling or adhering to intended substrates). Many new applicators have problems with falloff.
The thicker the wall, the more weight is pulling on the sprayed insulation. Therefore, it is very important to know the fiber-to – water ratio and keep it consistent. The thicker the walls, the more important this becomes.
The wider the distance between the studs, the less surface area the sprayed material has to attach itself to. Thus, 16" on-center stud spacing is much more forgiving than 24" on-center stud spacing. In framing with 2 X 8s, 24" on-center studs can be sprayed successfully with the right equipment and material.
The angle of the nozzle and the velocity of the material are the two most important factors to reduce falloff. The sprayed insulation must hit the substrate and stay. This can be achieved only with the proper angle. If the angle is not correct, the material will tend to deflect or slide off the studs and substrate. This can be mastered with practice and training.
A “stud scrubber,” a rotating brush that grooms the insulation level with the face of the studs, is the best tool for cleaning down walls. Scrubbing typically can be performed immediately after the spray-on application. The product does not have to be dry in order to plane the wall cavity. Recycling of excess material is also performed as the installation process progresses. Normal drying will occur within 24 to 48 hours depending on climatic conditions, depth of fill, and initial moisture content. The manufacturer’s recommended drying times should be followed.
Recycling the excess material translates to very little waste, although it can be more time-consuming. The material must be mixed properly when recycling, or problems are likely to occur. If the material is mixed improperly, the wall cavity insulation may be too wet, causing inconsistent flow and leading to instability, and the insulation may fall out of the wall cavity. The moisture or fiber volume must be adjusted carefully when the recycling method begins. The recycled material adds moisture mixed with the dry product. Adjusting the water pressure or changing the spray tips will help maintain the same moisture percentage throughout the job.
Installation of the interior finish should not be done until the insulation has dried. This should be monitored using a moisture meter. (СІМА recommends the Wagner Electronics Model L6101.) The wet-spray cellulose may be enclosed when it is sufficiently dry, having a measured moisture content of 25 percent or less.
Wet-spray cellulose can be applied successfully in freezing conditions, but the manufacturer should be consulted for recommendations on spraying in severe climates and conditions. Since the entire spray system can freeze up, heating the building while spraying is necessary if the temperatures are below freezing. After the spraying is completed, the heat can be turned off. The windows should be opened in order to facilitate air movement and moisture removal. If heat is used during the drying process, it is imperative to have ventilation to the outside. Dry heat, such as electric, works the best. It will speed up the drying process. Propane or gas heat can add high percentages of moisture and should be avoided.
The wet-spray cellulose will take longer to dry in colder climates. If ambient temperatures are expected to drop below 40°F before drying is completed, it may be necessary to use supplemental heat until the moisture content measures 25 percent or less.