Rising energy prices have contributed to the development of heat pump-based heating systems in Sweden. Low flow temperature in the secondary heat distribution system to rooms is a requirement for energy-efficient systems. This increases the thermal efficiency of the heat pump and decreases thermal losses in the distribution system. Flow temperatures in water-based systems for heat distribution in buildings have been decreased from 55°C to temperatures around 30°C. This is to maximize the efficiency of heating systems that are based on heat pump technology. Different technical solutions have been suggested to guarantee space-heating requirements with low temperature difference between heating units and ambient air. Floor heating has in many cases been considered a good option, and the popularity of such systems has dramatically increased. Complicated installation work, moisture problems and slow thermal control with floor heating are reasons enough to find alternative low-temperature units for heat distribution in rooms. This may result in a combined heating and ventilation system that operates with forced convection.