Special design | Clay plaster on gypsum board or concrete without dew point monitoring R+D in the seminar room of the Unicampus

As part of a study by the Balearic Island's University, the Engineering Group of Building and Energy Management has shown that radiant heating and cooling systems require significantly less energy than conventional heating/cooling systems. Radiant cooling in itself has an energy saving of 30% compared to conventional systems (fan coils or split air conditioners) and offers the optimal operating temperatures for geothermal and solar thermal energy. In addition, surface systems are ideally suited to heat and to air-condition existing or listed buildings, as retrofitting is associated with low costs and impact on the structure.

In 2015, a surface heating and cooling system was installed for testing purposes in a seminar room built in the late 80s on the university campus in Mallorca. The system consists of Clina capillary tube mats, a well (as a source for ground cooling), a solar collector, a storage tank (300 litres), a photovoltaic system with connected air-to-water heat pump, a ventilation system as well as control and monitoring systems. 

In order to reduce the proportion of grey energy, the ecological and traditional materials clay and straw were used for the ceiling construction. In addition, these materials have the advantage of being hygroscopic, i.e. they keep the humidity in the interior rooms very stable throughout the year. The ceiling was closed with calcium silicate panels, which have a high fire resistance and are again hygroscopic, so the system does not need a dehumidifier for cooling. The excess moisture can easily be removed by ventilation at another time when the chilled ceiling is off. By using these alternative materials for the ceiling structures, the installation takes more time and is (still) more expensive as it is not up to standard, but has a 50% lower CO2 emission than conventional raw materials.

The system was tested and data collected for over two years. The results show that the desired ambient air temperatures (18°C in winter and 26°C in summer) and humidity (65% relative humidity) can be maintained during the entire period. The heat pumps and solar collectors never have to provide more than 40°C, as the large surface area of the capillary tube mats means that the supply temperatures are always around 18°C. In addition, with appropriate control, a very even heat transfer could be observed throughout the room. 

The heating and cooling system uses the available renewable energy all year round and only requires a small amount of electricity for pumps and auxiliary systems. Combined with solar collectors and photovoltaic systems, 85% (summer) to 95% (winter) of the energy costs can be saved. Especially in Mediterranean countries, all thermal needs (heating, cooling and domestic hot water) could be covered with today's highly efficient systems.



plaster ceiling


Project title

UIB Universitat de les Illes Baleares Palma Mallorca


Palma Sola / Mallorca

Building type

public building


CTM surface

148 m²