Blown Insulation in Attics: Installation, Tips and Best Practices
If you're an environmentally conscious builder, you'll want to consider installing loose-fill insulation in an attic. Loose-fill insulation is available in a few options — fiberglass, cellulose and mineral wool — all of which contain recycled materials. Fiberglass consists of almost a third of recycled glass, spun into fibers. Cellulose is made from recycled, shredded newsprint and boxes that have been chemically treated for fire and mold resistance. Mineral wool is made from slag and rocks that are recycled from industrial waste.
When installed properly, loose-fill insulation improves the energy efficiency of a home, lowers utility bills, and decreases fossil fuel burning and carbon dioxide emissions. To ensure that homeowners reap these benefits, builders need to follow manufacturers' installation guidelines and check for the following:
- Correct R-value A material's thermal resistance is measured by R-value. Because each of these loose-fill insulation materials has a different R-value, you'll need to install them at different densities in order to achieve an adequate level of insulation. You'll also need to adjust for the amount of settling that will occur over time and affect the installed R-value. Cellulose loses 20% of its R-value, so you should add 20 percent more in an attic during installation. The settling percentage of fiberglass and mineral wool is minimal and doesn't affect thermal performance.
- No gaps or fluffing If insulation isn't installed at the right density, voids and gaps can form, lessening the R-value. Fluffing also weakens the effectiveness of insulation. When insulation is fluffed, it's installed to minimum thickness but not to minimum weight requirements, allowing air and heat to pass through it.
- Appropriate placement Loose-fill insulation works well in attics because it's the most cost-effective place to install a large amount of insulation. Although you're covering a large area, you want to be careful not to block ventilation and to keep insulation at least 3 inches away from ceiling fixtures. Install baffles above soffit vents, and block soffits to prevent moisture and mold problems. Make sure ductwork is properly sealed to prevent insulation from circulating into the home.
- Adequate drying Make sure the loose-fill insulation has enough time to dry before the drywall is installed. For instance, if cellulose insulation is not completely dry, it will not meet R-value requirements.
Loose fill is an effective, environmentally friendly option for insulating attics, as long as it's installed according to manufacturer's specifications.
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