R Value: A term you need to know when upgrading attic insulation

R Value: A term you need to know when upgrading attic insulation

Before you choose attic insulation, it's important to learn the efficiency rating of the different materials to ensure a high return on investment. Just like a furnace rated 90 annual fuel utilization efficiency (AFUE) outperforms a system with an 80 AFUE, some insulation performs better than others. R Value helps you conduct a side-by-side comparison.


The term itself denotes insulation's capacity to resist the movement of heat through it. That's where the "R" in "R value" comes from. So, the more an insulation can resist heat, the more efficient it is.

Insulation ratings

As a baseline, the efficiency of a solid piece of wood has a 1 R value. It doesn't resist heat very well, but insulation does. R value generally depends on the materials used to manufacture the insulation and the density of those materials.

Batts and rolls. This kind of insulation is generally constructed from rock wool or fiberglass. The rolls/batts fit between wall and floor joists. Batts that fit between a 2 by 4 inch area are rated between R-13 and R-15, while rolls that fit in a 2 by 6 inch space are rated between R-19 and R-21.

Foam in place. Installers generally use this kind of insulation as a blown-in material, as it fits nicely into tight spaces and crevices, effectively sealing the area to stop air leakage. Closed-cell foam insulation achieves a rating of about R-6.2 for each inch, while open-cell foam insulation is rated a little lower, because it's not as dense, at R-3.7.

Rigid foam insulation. This very dense material costs more than batts or rolls, but it's also more efficient—so you can use less of it. Per inch of insulation thickness, the material is rated R-4 to R-6.5, which offers about twice the efficiency of other insulation per inch of material.

No matter type of insulation you choose or the efficiency rating of the material, you'll get best results from proper installation. A poor insulation installation can reduce the expected performance of the material, and decrease your return on investment and comfort potential.

For help reviewing insulation efficiency or selecting a material, contact the experts at Findlay Roofing today! We're happy to help with home insulation, window replacements, or roofing repairs.

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