<p>Previous studies on the moisture buffering characterization of hemp concrete have shown some discrepancies and difficulties for comparison. The aim of this paper is to raise warning points and define a robust protocol for Moisture Buffer Value (MBV) measurement of vegetal concrete. The applicability of the NORDTEST protocol was assessed by two round robin tests (RRT) on an industrial hemp concrete. Seven laboratories participated to the RRT. The first RRT specified a method for the conditioning of specimens prior to the MBV test, without added recommendation. Based on the shortcomings of the first RRT, a second RRT was performed with additional recommendations. For the test, the specimens should be representative of in-situ ones regarding exchange surface and orientation versus moisture flux. RRT2 confirmed that the exchange surface finishing widely affects the MBV results. Moreover, it underlined the effect of air velocity and the least efficiency of climate chambers with Peltier technology. The results obtained following this more detailed protocol were comparable between laboratories, suggesting their robustness to assess MBV of vegetal concrete.</p>