Design, construction and validation of a guarded hot plate apparatus for thermal conductivity measurement of high thickness crop-based specimens

Written by esba

The search for sustainability achievement in the building sector led to the use of crop-based insulation materials. Among these, raw products like plant straws bales can present elementary representative volumes in the order of several square centimeters. Fibers orientation may play an important role in material thermal behavior. Measuring their thermal conductivities with standard steady-state equipment can thus lead to some inaccuracies due to the necessity of resetting lower thickness samples. This paper presents a guarded hot plate apparatus designed to test high thickness samples, up to 40 cm, with an accuracy of 2 %.

The different parts of the machine are described in detail along with the design process and challenges encountered. Temperature and heat flux measurements in the device represent critical design stages where optimal accuracy is needed in order to optimize the resulting global error. Regarding this, necessary numerical and experimental analyzes were conducted emphasizing intrinsic systematic error assessment. To complete the study, some validations tests are performed on reference material and other widely-spread polystyrene slabs. These tests take into account the optimal computation parameters resulting from the numerical analysis and the apparatus proved to be in accordance with accuracy requirements.


  1. Dubois, S.
  2. Lebeau, F.


About the author


The European Straw Building Association is an independent European association, devoid of any profit making motive. The object of the Association is to promote and develop the use of straw, as a sustainable way of building in all the senses of the term “sustainable”: renewable, ecological, healthy, energy and climate efficient, social and economic.
The Association is a federation composed of organisations and people particularly concerned with the use of straw in buildings.