U-value is a measure of thermal conductivity, and is the inverse of the more-often-used R-value, which is a measure of thermal resistance. A higher U-value of an insulation material or assembly means more thermal conductivity—in other words, less insulation value. And a higher R-value means just the opposite: better insulating qualities. 

    Actually, it’s not quite that simple because U-value is a more complicated evaluation that includes consideration of convection and radiation heat losses, but they are approximately the inverse of each other. So, when evaluating insulation, a lower U-value and a higher R-value are what you want to see.

    Although U-value is often used in energy efficiency calculations, most people are only familiar with the R-value of insulation. The only place we commonly see a U-value is on the HUD data plate of a mobile home, because HUD standards are based on U-values. 

    Conversion to R-value from the data plate from an of an older mobile home shown above is simple. So, for example, the R-value of the insulation of the walls of this home is 1 divided by .048, which is approximately R-20. The ceilings would be 1/.058 = approximately R-17, and the floors are 1/.034 = approximately R-30.

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Here’s links to a some of our blog posts about INSULATION: 

• What are the common problems with attic insulation?

• Why is vermiculite attic insulation a problem for both buyers and sellers of a home? 

• How can I tell if a house has insulation? 

• Why is spray foam used for attic insulation?

• Should I put some more insulation in the attic?

• What does the "R-Value" of home insulation mean? 

• What is minimum requirement for the insulation of a mobile/manufactured home according to the HUD-code? 

• How energy efficient is a mobile home?

 • Why is insulation not allowed to touch around a gas flue in the attic even if it’s not flammable?

• Is cellulose insulation flammable? 

    Visit our INSULATION page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.