Nowadays, very strict thermal and technical requirements for thermal insulation of passive building envelopes are imposed and thus, individual structures need to fulfil severe technical criteria. In order to comply with the passive energy standard in the Czech Republic, heat flow losses in buildings need to be minimized and the air tightness of their envelopes has to be kept between n50 < 0.6/hour. This can be achieved by using thermal insulation materials of considerable thickness and complete airtight sealing of structures, both on the surface and in critical details. However, meeting these requirements might cause problems in the summer months when interiors tend to overheat, reducing users ́ general thermal comfort as well as thermal stability of the building. This may be solved by using natural or forced ventilation which is, nevertheless, very often rather inconvenient to operate and generally requires a lot of space. Thus, the best way to improve thermal stability is to improve the properties of the structure itself, especially of the roofing which is frequently a source of problems. Therefore, it is advisable to focus on increasing the specific heat capacity and choosing a construction material with the highest possible weight. This will delay the rise in temperature over time by increasing thermal damping time and finally lead to increased interior temperature stability. However, the increase in energy which is needed to increase the temperature of the shell is closely connected with the risk of accumulation of heat gains. This is considered to be a potentially undesirable effect which may significantly reduce users ́ thermal comfort. This paper aims to address this particular issue, focusing especially on the incorrect application of used systems and inappropriate conception of internal operation. The paper introduces an idealized experimental model computed by the CTF method (Conduction Transfer Functions) which was used to compare material shells and traditional structures as well as to assess the influence of orientation of material shells to the cardinal points on accumulation of temperature gains in the structure.