HESmix has been tested according to EN standards in laboratories and by Professors and has achieved outstanding results for thermal, moisture, fire, compression and more.

In this post I’ll be diving into the technical aspects of our thermal conductivity tests and results.

We have test results at varying densities: The Lambda at a density of 319kg/m3 = 0.063 (test results here)

The Lambda at a dry density of 239kg/m3 = 0.057 (can be found here)

In our buildings, depending on the area of application (roof, wall or floor) our material densities differ.

WHAT DOES THIS MEAN ?

due to the relation between thermal conductivity and density as can be seen by observing the results of our tests as well as can be read in this thesis we are able to Calculate thermal conductivity in relation to material density.

What is Thermal conductivity

The thermal conductivity (lambda or K-value) is the measure of materials ability to conduct heat and is measured in units of Watts/meter.kelvin (W/m.k)

How to calculate determine the thermal conductivity in relation to density.

The difference in thermal conductivity between material at 239kg/m3 and 319kg/m3 (difference of 80kg/m3) is 0.006 W/m.k

that is equivalent to an increase of 0.000075 W/m.k / 1kg/m3 increase in density. (0.006/80kg/m3)

therefore the thermal conductivity of a material 70kg/m3 less dense has a Lambda of 0.0052 (0.000075x70) lower than its base.

E.g.

169kg/m3 = 70kg/m3 (less than base)

0.057 - 0.0052 = 0.051 W/m.k

Or

259kg/m3 = 20kg/m3 (more than base)

0.057+0.0015 = 0.0585 W/m.k

U-value, what is it ?
This is a figure which most architects and/or engineers require during the design stages in order to comply with energy standards and receive compliance certificates during building permitting.

U-value is expressed in W/m2.k and is used to determine the thermal resistance (R-value) and is calculated by dividing the Lambda by the thickness of a material. Most energy codes require a maximum U-value for various parts of a building. U-value is the overall heat transfer coefficient of a material or building element.

Calculating U-Value from Lambda

eg. a wall with a density of 240kg/m3 and a thickness of 35cm has a u-value of:

0.057W/m.k /0.35m = 0.162W/m2.k or

a roof insulation with density of 169kg/m3 and a thickness of 35cm has a U-value of:

0.051W/m.k /0.35m = 0.145W/m2.k

Calculating Minimum thickness from Required U-value

if you require a maximum U-value of 0.18 and the material Lambda = 0.057 (HES-mix at 240kg/m3), Then how thick should your walls be? 0.057/0.18 = 0.32m thick or a minimum of 32cm thick.

If you have any questions or comments please send them to me.

Yours in HempLime

Toni Läderach

Engineering and Technology

HES-Group