Thermally Activated Building Systems (TABS) are a popular and energy efficient way of heating and cooling buildings. Due to the water temperature that is very close to the room temperature they are seen as one of the most energy and exergy efficient heating systems. TABS have high innertia and respond only slowly to control inputs. Several control issues have already been resolved in the past e.g. time of operation, intermittent pump operation etc. This articles further investigates control issues and shows how energy efficiency of TABS can be improved with better water temperature control and optimisation of the dead-band, which should not be larger than 2 K.