# How to calculate the thermal conductivity of a composite material

Very new to thermal conductivity calculations, so I'm aware there are already queries on here that may cover this, but I'm struggling to apply them to this instance.

I'm trying to calculate the U-Value of a composite material. The data I have is the thickness of the materials used, and their thermal conductivity in W/mK. How do I use these to calculate the thermal conductivity of the material as a whole?

My attempt so far has been to calculate the individual R-Values by dividing the thickness of the material in metres by the W/mK, and then sum those R-Values, and then divide 1 by that sum to get a U-Value. I'm sure I'm off somewhere though, as the U-Value has ended up huge!

Appreciate any assistance, fairly sure it's a simple answer for someone familiar with the topic!

• Think about them like parallel resistances. Feb 23 at 10:22
• First result of a google search; kingspan.com/tr/en/knowledge-articles/… Feb 23 at 10:23
• Thanks, does that mean that the method I've described above is actually correct? Feb 23 at 10:27
• Anything divided by 1 stays the same so no. Feb 23 at 10:29
• Sorry, typo! Edited now - I'm dividing 1 by the sum of the individual element's R-Values to arrive at a U-Value Feb 23 at 10:34