This work presents a comparative study between two buildings or cubicles with a same geometry and orientation but with different constructive layers. The mineral wool cubicle is more insulated whereas the alveolar cubicle has more thermal inertia. A novel point in this study has been to evaluate indirectly the thermal load based on the energy consumption of the heat pumps. The results indicate that the mineral wool cubicle consumes up to 7.3% less energy consumption than the alveolar cubicle, particularly in summer. In fact, the load in summer is up to 11.6% higher with the alveolar cubicle, which gains more solar energy during daytime due to its inertia. The power consumption is practically aligned with the outdoor temperatures since it is very sensitive to the operating temperatures. Nevertheless, the peak building load can take place up to 5 h later than the peak outdoor temperature, particularly in summer and in the alveolar cubicle. Finally, the proposed approach has helped obtained in situ U-values of 0.20-0.27 W m(-2) K-1 for both cubicles. (C) 2015 Elsevier B.V. All rights reserved.