Cellu-Spray for Builders

If you are familiar with insulating a house with fiberglass you know that it is cheap but nasty stuff. Spray applied, loose fill (dry) or dense pack (dry) cellulose installed by Cellu-Spray is a far superior product. It will make for a tight, quiet, and most importantly, an energy efficient building. You can rest assured that you won’t be fielding calls about frozen pipes, mice, mold, or cold rooms if you choose Cellu-Spray to insulate your project. As a certified Nu-Wool installer Cellu-Spray can provide your clients with an Energy Guarantee. No other insulation offers such a guarantee and you can use this as a selling point to prospective clients. 

By building a tight, energy efficient shell you can reduce the size of the heating and cooling equipment and use those savings to pay for the additional upfront costs of a better product. Cellu-Spray can work with you and your sub-contractors to properly size the heating and cooling equipment. We can also supply diagnostic services such as Blower Door testing and infrared camera scans for both new and existing buildings. We are your thermal envelope experts.

New Construction

There are basically two ways that we insulate with new construction, spray applied cellulose in wall assemblies and dense pack cellulose in cathedral slopes or closed cavities such as floor assemblies or rim joists. For vented, flat attics loose fill cellulose is used.

Spray Applied


Spray applied cellulose or “damp spray” is installed with water added at the tip of the hose. We use high pressure hoses and the water is added in extremely fine drops as a powerful mist. This action combined with the relaxed cellulose fibers means that when the cellulose slams into the sheathing it builds up on itself, filling the entire stud bay. We spray the cellulose past the studs and they are then scrubbed down with a mechanical scrubber. There is no chance for any gaps or settling to occur. We use the minimum amount of water to get it to stay in the bays and easily achieve a density sufficient to cause the material to stop the flow of air. The finished walls are then covered with sheetrock. We do not recommend a vapor barrier be added to side walls since it is an unnecessary expense and gives the wall assembly more drying potential if there is a wetting incident. 98% of vapor in wall assemblies is due to air flow and since there is effectively no air flow through a wall insulated with cellulose, you can skip the vapor barrier necessary with fiberglass.

National Fiber will provide a 24hr. drying guarantee if you use Cellu-Spray Insulation. The only times we have seen cellulose not drying fast enough to allow for sheet rock is due to the cellulose remaining uncovered and a source of moisture such as an unvented heater present in the building. In the winter we do need the sheathing warm to prevent the cellulose from freezing and slowing the drying process.

Dense Pack


Cellulose insulation can also be dense packed behind specially designed fabric which is stapled to the existing framing. We have a saying that we are "denser than you think" and take great pride in consistently installing cellulose past it's settled density. We will not blow in behind sheetrock if at all possible as we cannot inspect the density easily.

The fabric is stapled on the face and sides of the stud with a pneumatic stapler and after installation we roll each bay to ensure that there is no fabric bulging to interfere with drywall. Dense pack installations make sense for small projects or where there is a lot of stuff on the floor which would prevent vacuuming or clean-up. With Dense pack there is more prep time but less clean up.



Cellulose is an excellent material for retrofitting existing buildings. Typically this is done by accessing the wall bays from the outside of the building. If the building is un-occupied then drilling through the interior takes less time and is therefore more affordable. These type of jobs need to be planned carefully as they use small amounts of material and huge amounts of time. The best times to access walls in an existing building is when the siding is going to be worked on. Having poor performing insulation such as fiberglass in the walls means that all that material would need to be removed prior to installing dense pack cellulose.