TECHNICAL STUDIES RELATED TO THE HEAT INSULATION OF STRUCTURAL ELEMENTS

MESSTECHNISCHE UNTERSUCHUNGEN UEBER DIE WAERMEDAEMMUNG VON BAUTEILEN

TECHNICAL DETERMINATION OF THE HEAT INSULATION OF POROUS, MOIST MATERIALS MAY BE CONSIDERABLY INFLUENCED BY THE MOISTURE MOVEMENTS, MOISTURE ABSORPTION AND MOISTURE EVAPORATION WHICH TAKE PLACE DURING THE PROCESS OF MEASUREMENT. MEASUREMENTS WERE UNDERTAKEN TO CLARIFY WHETHER CERTAIN CONDITIONS WERE NECESSARY FOR THE MEASUREMENT IN ORDER TO AVOID ERRORS. THE TESTS, WHICH WERE CARRIED OUT WITH REFERENCE TO GERMAN STANDARD DIN 52611, WHEREBY THE SAMPLES WERE STEAM SEALED ON THE SIDE OF THE HEAT OR ELSE REMAIN FREE, WERE CARRIED OUT ON THREE TYPES OF CONCRETE WITH VARIOUS BULK DENSITIES AND DIFFUSION RESISTANCE NUMBERS (GAS CONCRETE, STYROPOR CONCRETE, EXPANDED CLAY CONCRETE). IN THE CONCRETES WITH THE HIGH DIFFUSION RESISTANCE VALUES, I.E. THE STYROPOR AND EXPANDED CLAY CONCRETES, THE COVER HAD NO INFLUENCE ON THE RESULTS OF THE MEASUREMENTS IN THE MOISTURE AREA OF THE MATERIALS STUDIED, UP TO ABOUT 10 PERCENT OF THE VOLUMETRIC MOISTURE CONTENT. IN CONTRAST, IN THE GAS CONCRETES, IN UNCOVERED SAMPLES HAVING MOISTURE CONTENTS OVER ABOUT 1 - 2 PERCENT, THERE WERE SIGNIFICANTLY GREATER HEAT CONDUCTIVITIES THAN WITH THE STEAM SEALED SAMPLES. THIS CAN BE EXPLAINED BY THE FACT THAT THE UNCOVERED SAMPLES GIVE OFF MOISTURE NOT ONLY ON THE SURFACE OF THE COLD SIDE BUT ALSO ON THE SURFACE OF THE HOT SIDE DURING MEASUREMENTS. IN ORDER TO OBTAIN COMPARABLE MEASUREMENTS IN ALL CASES, MATERIALS HAVING A HIGH STEAM PERMEABILITY (FOR EXAMPLE GAS CONCRETE) HAVE TO BE STEAM SEALED ON THE HOT SIDE DURING THE MEASUREMENTS. THIS IS THE CASE WHEN CONVENTIONAL LARGE-SURFACE HEAT CONDUCTION METERS ARE USED.