Using Ceiling Heating as a Cooling Ceiling

Retrofit a Cooling Ceiling - Enjoy the Summer at Home 

With the FLEXIRO ceiling heating drywall set, you can also keep rooms cool in summer without noise and save energy. With cooling water supplying the heating system, the ceiling heating becomes a cooling ceiling. The room heat is absorbed by the cooled ceiling and removed via circulating cooling water. The result: the room cools down evenly, pleasantly and without affecting your health. The heat is transported upwards by heat radiation from surfaces and people in the room, as well as by the warm room air, which rises to the ceiling, cools down there and descends again in a cooled state. The effect of ceiling cooling is achieved via the surface. The position of the 10mm PE-RT pipes close to the surface, integrated in the drywall elements, increases its efficiency. Disruptive effects of an air conditioning system, such as cool drafts and noise, are avoided.

The central challenge for the use of ceiling heating as a cooling ceiling is the sufficient supply of cooling water over a longer period of time. Approximately 10 l of cooling water with a water temperature of 17-18°C must be pumped through the ceiling system every hour per square metre of active surface.

Where does the cooling water come from?

The need for cooling water limits the possible applications of a cooling ceiling. What sources are suitable for operating a cooling ceiling? 

Solution 1Passive heat pump

Heat pumps are a convenient and cost-effective technology. If a geothermal heat pump can be operated, the cooling water that's needed can be provided by passive cooling alone. The lower temperature in the ground is enough to sufficiently cool down the water temperature for the cooling ceiling via a plate heat exchanger. With passive cooling, no heat pump compressor is required. This keeps electricity consumption low. Disadvantage: The ground can only absorb a limited amount of recirculated heat. In long and hot summers, the cooling capacity of the ceiling can thus decrease.

Solution 2Reversible heat pump

The ceiling can be actively cooled with a reversible heat pump, either in the form of brine-water or air-water pumps. The reversible heat pump works as a cooling unit in summer and as a heating system in winter. With this technology, you achieve a reliable cooling supply even at high summer temperatures.

Solution 3Split refrigeration

If the existing heating system needs to remain unchanged, split refrigeration technology is the ideal solution for supplying cooling water. In this technology, the evaporator and condenser are separated from each other. This means that the low-noise, air-cooled condenser can be installed outdoors without any problems, while the evaporator can also be installed inside the building.

Solution 4Use of natural temperature sinks

If natural temperature sinks such as well water, water from cisterns or flowing or stagnant open water are considered for cooling the cooling water, it must first be checked whether the energy content of this reservoir is sufficient to supply the cooling ceiling with cold for several hours a day. It must also be ensured that the natural cold source has enough time to regenerate the temperature within the operating time of the cooling ceiling. The recirculation of water with increased temperatures back into nature must not cause any damage. If necessary, an official permit is required for recirculating the heat.

What must be taken into account when operating the cooling ceiling?

Every cooling ceiling must be protected against the humidity of the room air condensing on the ceiling. This is reliably prevented by always setting the supply temperature of the cooling water slightly higher than the dew point temperature at which air humidity begins to condense. You can find out from the weather service how high the usual dew point temperature is in your region. As a rule of thumb for Central European climates, the cooling water temperature must be set to a minimum of 16°C as the lower value so that the temperature doesn't fall below the dew point. Taking into account a safety buffer, a flow temperature of 17-18°C should be set for cooling at the cooling generator or heat pump.


Cooling capacity in [W/m²]

Average cooling water temperature*




Room temperature







Cooling capacity in W/m2







 *For the FLEXIRO cooling ceiling, a ∆T of 2K between flow and return is recommended

Unfortunately, it is not possible to control the room temperature in cooling mode using the Easy4 and Easy RTL4 Kompa boxes offered. The Kompa boxes are designed exclusively for heating operation. Mechanically functioning thermostatic heads have no reverse function. The room temperature is alternatively controlled via the supply temperature control. If the thermostatic head is set to the highest value, the valve is always open in summer and the cooling water can flow into the ceiling cooling system. If the room cools down too much, the flow temperature is increased at the cooling generator or heat pump until the room temperature is comfortable.

Other solutions for controlling a cooling ceiling are possible but also cost-intensive. In view of the sizes of the sets available, the purchase costs for additional control technology are only worthwhile when operating larger cooling surfaces.