First house with Isomax system in Murska Sobota

In 2009, we made the first residential building with the Isomax system in Slovenia. The system was also designed with a central solar collector for preheating hot water. The system exploits the coolness of the earth with a cold cursory storage tank.

Ventilation is performed with an earth tube conveyor tube-to-tube and a mixing ventilation component for summer and winter operation. The system consumed 14.6kWh / m2 per year.


Family house in Dobrava

The dwelling house is designed with a flat earth tank built under the foundation slab. Beside the slab is additional thermal insulation installed horizontally to reduce the influence of the outside temperature on the warm underground storage tank. The house is built with modular brick blocks which are 30 cm thick. 

Thermal barrier pipes are laid throughout the exterior wall. The thermal barrier is also put in the attic by the concrete slab. In this way, a temperature barrier is along the entire sheath. The rooftop has solar collectors and a smaller solar power plant. A smaller water/water heat pump is used to cover the tips and to heat the sanitary water. For cooling in summer, we use groundwater to cool the temperature barrier passively. Only the passive mode cools the house and offers a comfortable living comfort. Energy consumption is 7.6 kWh / m2 per year. If we subtract the energy gained from PV panels, this energy is only 3.4 kWh / m2 per year, with the house being built in low energy mode of 28 kWh / m2 per year. With the help of the Solinterra system, energy can be reduced by almost ten times. The energy required for the operation of the house is for heating, cooling, preparing sanitary water (6 members) and ventilation by heat recovery.  


MIC Nova Gorica

The world's first zero-energy school with Solinterra.

How to make a low energy building a zero energy building only by using natural energy sources?

Purpose of the project was to convert a low-energy building into a zero-energy building, without changing the thermal sheath, but remaining the same. According to the preliminary design, the facility was connected to remote heating.

For cooling purposes, a 428kW cooling generator on the roof was provided. Ventilation was designed on exploiting 65% of wasted heat.

The preparation of hot water in the heating season is carried out with remote heating and in the rest of the year with electric heaters. According to the actual energy use, the heating facility would have consumed around € 58,252 for remote heating per year. For cooling with the cooling generator, it would've consumed € 27,440, for the preparation of hot sanitary water € 2,040 and ventilation € 6,510. The total cost for heating, cooling, ventilating and hot water preparation would be € 94,242 per year.

Our knowledge and development helped us design and build our first building which consumes extremely little energy and exploits natural energy sources. We've used this technology before with smaller buildings, but this facility was our first bigger project.


The most important elements of Solinterra system are: 

  • thermal barrier (pipes laid in loops on the outer wall under insulation and all over the outer sheath, together with the plaster, form a barrier that prevents the walls or interior from cooling or overheating
  • Active concrete core (this means that the entire mass of concrete in the inter-floor slabs heats and cools
  • underground heat storage tank under the facility (for storing free solar energy in summer, 320m2 of solar collectors on the rooftop receives the power, the warmth is saving under the MIC facility in the ground)

A high-temperature and efficient water/water heat pump is also installed to cover the tips after heating and for the preparation of hot water. The heat pump is only 70/80 kW. 

In individual rooms are installed parapet and ceiling convectors, which cover the tips after heating or cooling.

Ventilation was performed with very high-efficiency heat recovery systems up to 90% and with integrated heat pumps with Dx unit for cooling and heating. The devices also incorporate CO2 sensors that allow optimally fresh air to exchange and ventilate the building. That way, we save a significant amount of the energy required to operate the fans.

All fans have built-in highly efficient EC motors.

Solar collectors are mostly used for DHW (domestic hot water) heating. 84% of the sanitary water is prepared using solar collectors only, and a water/water heat pump heats the rest. 

The cooling is performed in such a way that the groundwater energy is utilized.

Through the flat exchanger, the energy of the cold is utilized. In this way, cold water is used to cool the temperature barrier and the concrete core and the convectors.

The CNS system is responsible for the whole system, control and management. Over 380 sensors, flow meters, calorimeters, electrical power meters and control and monitoring systems are installed throughout the control system. Based on this information, all the energy required for heating and the actual energy consumption is stored and recorded.

In the introduction, it was presented how to make a low energy facility (35 kWh / m2 / year) that uses as little energy as possible for heating.

We have succeeded with our knowledge and experience since the facility consumes less than 2 kWh / m2 per year for heating without saving energy or heat in the building.


In classrooms and offices, the average temperature is between 22.5 and 23.5 ° C and in the workshop, between 21-22.5 ° C.

If the facility were heated to the temperature prescribed by the project or policy, it would save another 8-10% of energy. With such low energy consumption, this is practically not worth it, and school users are pleased to keep them warm in the winter. The facility uses only € 1,347 or 9,621kWhel for heating, and for a 5112 m2 large building that is only 1.88 kWh / m2 / year for heating.

The price includes all the electricity needed for operation: circulation pumps, motor drives, regulation and heat pump. 

Only groundwater energy is used for cooling, only a pump that draws 14.5 ° C cold water from a depth of 32 m, is used for cooling through the flat exchanger. 

Considering that the relatively high temperature is drawn, it is still low enough to allow the facility to cool down smoothly. This means that the facility can cool down, even though the outside temperature exceeded 40 ° C for several days a year.

The school had a constant temperature of 26 ° C throughout the summer. We didn't save on cooling as well. The cooling cost was € 1,036 or 7,407 kWhel., which is 1.45 kWh / m2 per year for cooling.  

The preparation of hot water was covered with solar energy for most of the year. The cost of the circulation pump and the additional heat pump is 150 € per year or 1,180 kWhel.

Ventilation represents the biggest expense for the facility.

The ventilation cost is € 2,060 for starting up the fans.

Procedure for determining energy savings:

The savings are mainly based on IDZ project documentation and PZI project documentation.

Analyzes have been made as well as various studies.

The results of the savings are demonstrable, as the facility has 11 heat and cold meters installed, as well as an electricity meter for the entire machine installations.

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