The big misconception is that people generally feel that if two insulation products have the same R value, then they must be the same, but they are not.
For example, during sub-zero temperatures, fiberglass insulation loses up to 50% of its R-value, where cellulose insulation gains a little when the temperature drops below zero.
R value is determined by tests done in a lab under a controlled environment.
It measures the conduction, the thermal resistance of heat as it transfers through the insulation product.
This does not include the insulation’s ability to resist air from passing through it.
The intention of the insulation is to stop the transfer of heat.
Cellulose insulation is the most effective and the most cost effective blown insulation for keeping energy costs down. It also helps keep your home comfortable and safe because it’s made from recycled newspaper. Cellulose is great for sound dampening, fire resistant, it prevents mold and mildew, and keeps out insects and rodents.
The R-Value of Cellulose is 3.8 per inch giving you an R-13.3 for 2×4 wall cavities and an R-20.9 on 2×6 walls.