Understanding R-Value Ratings and Insulation

R-Value Ratings

Understanding how R-value ratings relate to insulation is essential for home inspectors and new construction builders alike. Insulation with a higher R-value reduces the flow of heat between the interior and exterior of a building, helping to maintain a comfortable internal environment and lower energy bills.

Using standard Insulation Contractor, the R-value of an insulation material is calculated by measuring its resistance to conductive heat transfer. The R-value of an insulation material depends on its thickness, density and thermal conductivity.

A material’s R-value is determined by its resistance to conductive heat transfer divided by its thermal conductivity, which is a measure of how easily the material transmits heat through it. This is a simple calculation, but many other factors can influence the R-value of an insulation.

For example, the R-value of an insulation is influenced by its density and how tightly it is packed in place. Adding an extra layer of insulation does not always increase the R-value; rather, it may double or quadruple its thermal resistance. However, this linear relationship does not apply for compressible insulation such as batting or cotton.

The R-value of an insulation is also impacted by how it is installed. Gaps or compression can significantly reduce an insulation’s ability to resist thermal transfer. In addition, the moisture content of an insulation can negatively affect its R-value as well.

The ideal R-value of insulation for a specific home or project varies by climate. To learn more about how to properly select an insulation R-value, take InterNACHI’s free online course, Understanding R-Value Ratings.

Coastline Insulation
268 Serenoa Rd Unit 2B, Santa Rosa Beach, FL 32459
(850)-565-1027