How to Convert Metric U Value to Imperial R Value

U-values can be converted to R-values with simple algebra.
••• Jupiterimages/ Images

The rate of heat flowing through a material is determined by the material's R-value or metric U-value. The R-value is measured in the SI, or System International, units of Kelvin meters squared per Watt, or in imperial units, square foot degrees Fahrenheit hours per British thermal unit. The U-value has the inverse of R-value units, Watts per Kelvin meters squared. The greater the U-value or the lower the R-value, the more conductive the material will be. In conversation, the scale of the value implies which system is being used and units are not given.

    Multiply the U-value by 0.176. At this point, the units will remain the same, Watts per Kelvin meters squared. For example, begin with a U-value of 0.75 Watts per Kelvin meters squared. Multiplying through gives you (0.176)(0.75) = 0.132 Watts per Kelvin meters squared.

    Divide 1 by the product of 0.176 and the U-value. The factor 0.176 indicates that the R-value is not simply the reciprocal of the U-value since there is a conversion between units as well as the value. In the example above, dividing 1 by 0.132 gives you (1/0.132) = 7.58.

    Switch the units from the metric Watts per Kelvin meter squared to the imperial square foot degrees Fahrenheit hours per British thermal unit. This will distinguish the American R-value from the metric U-value. Therefore, the U-value 0.75 Watts per Kelvin meters squared translates to an R-value of 7.58 British thermal units per hour per square foot degrees Fahrenheit.

Related Articles

How to Calculate Metric Conversions
How to Convert Kilojoules to Kilocalories
How to Convert Kilopascals to Joules
How to Calculate Torsion Constant
How to Convert Conductivity Units
How to Convert Foot-Candles to Lux
How to Measure Meters in Feet
How to Convert Square Meters to Linear Yards
How to Find a Z Score
What Is MQ in the Metric System?
How to Write an Equivalent Fraction With a Given Denominator
How to Calculate a T-Statistic
How to Convert PSIs to KPIs
Thermal Properties of Paper
How to Convert an Area to Square Feet
What Is the Unit for Enthalpy?
How to Find Mass in Weight
What Are the Advantages or Disadvantages of Using the...
How to Convert a Durometer to Young's Modulus
How to Convert MBH to Tons