This paper presents application range and functionality of thermally activated building systems (tabs). Tabs are increasingly used for energy efficient and economical cooling and heating of commercial buildings. Thereby, the building structure is used as thermal storage allowing the use of renewable energy sources. Based on a simulation study for a typical office building the aspects of thermal comfort, maximum permissible heat gains in the room and the re-cooling of the building mass are analysed. It is shown that depending on the maximum permissible daily room temperature amplitude with tabs typical heat gain profiles with peak loads up to around 50 W/m(2) floor area can be managed. However, the transitional (mid-season) periods with already high solar gains and still restricted comfort range, in most cases will be decisive for the dimensioning of tabs, thus limiting maximum loads to lower values. The results also show that processes on the room side are almost unaffected from the processes on the supply side. In the cooling case, this allows for the re-cooling period of the fabric being extended to 24 h a day with accordingly "high" supply temperatures and peak load reductions of up to 50%. The results given may serve as orientation guide whether a tabs may be applicable in a specific building, and provides relevant parameters for the dimensioning of tabs. (c) 2006 Elsevier B.V. All rights reserved.