Quick Answer
Cellulose insulation has moderate fire-resistance properties, with a thermal integrity fire rating (T-25) or less, depending on the treatment and application.
Fire-Resistance of Cellulose Insulation
Cellulose insulation is typically treated with fire retardants to enhance its fire-resistance properties. The most common treatment involves applying a borate-based fire retardant, which can reduce the ignition point to 400°C (752°F). However, untreated cellulose insulation can still ignite at temperatures around 450°C (842°F). To achieve a T-25 fire rating, cellulose insulation is usually subjected to a treatment process involving borates, phosphates, or other fire retardants.
Thermal Performance of Cellulose Insulation
Cellulose insulation has a relatively high thermal performance, with R-values ranging from R-3.5 to R-4.1 per inch (25.4 mm). This makes it a suitable choice for wall cavities, attics, and floors. When properly installed, cellulose insulation can reduce heat transfer by up to 70%. To achieve optimal thermal performance, it’s essential to ensure a tight fit and sufficient installation depth, typically between 6-8 inches (152-203 mm).
Comparison with Other Natural Insulation Materials
Compared to other natural insulation materials like sheep wool (R-3.5 to R-4.0 per inch) and hemp (R-4 to R-5 per inch), cellulose insulation has a slightly lower thermal performance. However, its lower cost and wider availability make it a competitive option for many builders and homeowners. Additionally, cellulose insulation is often more readily available than other natural insulation materials, which may require specialized sourcing and installation procedures.
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