The need for more energy efficient Heating Ventilation and Air Conditioning systems led to a search for new systems for heating, coolingand ventilation of buildings. Strong reduction of energy consumption within the built environment is necessary because of the growing effects ofdepletion of fossil fuel and global warming. This lead to a almost standard concept of energy efficient office buildings in the Netherlands. Thatconcept exists of heat pumps and Low Temperature Energy Storage by aquifers combined with thermo active building systems (TABS). Thoughthere are many studies about TABS behavior they are mainly based on simulations and only a few actual field studies have been performed.Therefore last year we did measurements and held questionnaires to determine the perceived thermal comfort in two recently completed officebuildings with the TABS concept, as well as in two schools. This paper presents an experiment study in Netherlands where cooling in summerand heating in winter is provided by thermally activated building systems.