In ancient times, the most famous forerunners of modern thermoactive building component systems were the hypocaust heating installations of the Greeks and Romans, which used hot air or flue gases for heating floors and sometimes walls. The main examples of this technology today use air or alternatively water flowing through tubes. The system is most commonly employed for the thermal activation of solid floors by means of ducts concreted into the core of the element. A few years ago, it was estimated that roughly a third of all new commercial buildings erected in Germany incorporated systems for the thermal activation of construction components. Underfloor heating or cooling in screeds that are separated from the structural slab by insulation may be seen as a special example of this technology.