Spray-On Attic Insulation Options

Introduction to Insulation

• All insulation is designed to prevent thermal conduction and convection. All insulation is given an R value per a unit of thickness. Values can range from zero for uninsulated metals or masonry to upward of five for thermal batts and extruded polystyrenes. Each type of insulation has design restrictions specific to the manufacturer installation instructions, performance standards and warranty. In addition, each type of insulation has vapor and air barrier characteristics that should be considered by the designer or contractor planning your attic project.

Introduction to Spray-On Insulation

• Spray-on insulation is designed for attic insulation applications because of its high R values and its ability to conform to and fill irregularly shaped cavities. Spray-on insulation comes in a range of low- to high-expanding foams, can be open or closed cell and is composed of several chemicals. Spray-on rigid polyurethane foams consist of a polyol and an isocyanate. Various properties of the foam depend on the chemical ratio of the mixture, temperature, application and other factors. The foam chemically reacts in place during application generating heat and expanding to fill all gaps and corners.

Closed Cell Spray-On Insulation

• Closed cell insulation is designed for insulation and roofing. Density for insulation is 1.5 to 2 pounds per cubic foot for walls and ceilings and 2 to 3 pounds per cubic foot for roofing. Closed cell insulation expands 30 times from its liquid volume to solid volume at installation application and can be applied by an experienced installer at a thickness of 1/2 inch per pass or more. Closed cell foams combine the properties of a vapor and moisture barrier, air and water barrier, and insulation all in one. Closed cell insulation maintains a higher R value than open cell insulation because the chemical reaction forms bubbles that are captured for their insulating quality. Closed cell insulation is water impermeable.

Open Cell Spray-On Insulation

• Open cell spray-on insulation is designed as insulation only and does not provide a moisture barrier. During application, water is the blowing agent. The density of open cell insulation is slightly less than 1/2 pound per cubic foot and it expands over 100 times from liquid to solid volume. The excess, once cured, is trimmed flush to the framing and discarded. Open cell insulation uses bubbles of captured air as an insulator as opposed to the captured gas of closed cell insulation. Note that open cell insulation can be damaged by compression after installation. Open cell insulation is not water impermeable and will generally require a moisture vapor barrier .