Synopsis: Damp-spray cellulose might not be the first option you consider for insulation, but given its qualities — it’s cheaper than spray foam and air-seals better than fiberglass, with R-values comparable to both—you might want to keep it in mind. In this article, Leroy Anderson, the director of construction services for a New York City nonprofit group, explains why he likes damp-spray cellulose, then tells how he installs it in the projects he works on. Anderson says that installing damp-spray cellulose is a relatively low-tech process. One crucial factor is maintaining the proper ratio of moisture to dry cellulose; 25% moisture to 75% cellulose is ideal. A three-member crew is best: An installer mixes the moisture and cellulose, then blows it into wall cavities with it; a second worker uses a tool called a scrubber to level the slightly overfilled cavities; and a third worker vacuums the excess insulation for reuse. Damp-spray cellulose requires about 24 hours to dry before you can install drywall over it. This article includes sidebars about the safety of cellulose insulation and 10 things to know about cellulose insulation.

Insulating any building can be a challenge, but the non profit energy-efficiency and weatherization company I work for, Community Environmental Center, frequently insulates old houses being rebuilt for residential group homes and elderly housing in New York City. These skilled-care buildings are crammed with pipes, ducts, and wires, so they’re tough to insulate. They’re also located in dense urban neighborhoods that can be busy and loud.

For all these reasons, we use damp spray cellulose insulation in the majority of our open-wall insulating projects. Damp-spray cellulose fills cavities without voids, and it covers pipes and wires without gaps, creating a house that according to the Cellulose Insulation Manufacturers Association is 30% to 40% more effective at stopping…