R-Value is the imperial measure expression for how well a material resists the conductive flow of heat. The metric expression of RSI (en Francais, R-Value Systeme International) is the, "thermal resistance per unit area" of a material. It's easy to convert from one to the other:

• To convert from RSI to R-Value, multiply the value by 5.678
• To convert from R-Value to RSI, divide the value by 5.678

IMPORTANT: We want the MOST R-Value we can afford in our building. High R-Value is good! Insulators have higher R-Value than conductors.

The resistance capacity of a material is measured by the difference in temperature on the warm side of the material vs. the temperature on the cold side of the material.

So...actually, to determine resistance, we're measuring conductance. This is where U-Value comes in.