## 2 The Initial Technical Solution  
In terms of the method of operation of the ISOMAX system [1], the primary heat sources are solar and geothermic energy (Figure 1). The hot water can be reheated using an electric or gas storage water-heater. The energy (solar) roof collects solar energy (ESR). It is only useful in the summer and to a limited extent during the transitional period with sufficient heating of the heat transfer medium, i. j., at a temperature higher than the temperature in the long-term ground-heat storage. This source results in unstable and insufficient absorption of solar radiation (GHS). A less significant amount of geothermic energy is also trapped in the GHS for use as heating. Without boosting energy efficiency using a peak heat source, such as a heat pump or solar collectors, the ISOMAX system [1] employs solar energy stored in the GHS exclusively for direct usage in the thermal barrier (TB) and for preheating hot water. Due to the numerous fluctuating physical parameters affecting the solar radiation ESR, which only acts to charge the long-term GHS, it is difficult to determine the exact quantity of energy. Heat sources--ESR and GHS--are difficult to regulate and cannot meet the sudden requirements to increase the heat supply for heating and hot water. Additionally, they cannot meet the yearly energy requirements for heating, hot water, or ventilation. The ISOMAX system's source design [1] is typically implemented empirically through estimation [2]. By implementing a thermal barrier (TB) in the exterior structures to utilize the heat that is stored in the ground heat storage (GHS) or the cold that comes from registers of pipes buried close to the building below ground level at a depth of 1 to 2 m, the ISOMAX system eliminates heat loss/gain in the interior of the building (Figure 2) [1,2]. The thermal barrier is a network of pipes installed in the building structure between the static bearing and thermal insulation portions, as shown in Figure 3, or in the load-bearing portions of reinforced concrete panels that are divided into interior and exterior sides by thermal insulation, as shown in Figure 4. ISOMAX has technical solutions for applying both of the mentioned alternatives (Figure 5). For the production of self-supporting reinforced concrete panels, it applies lost formwork, and concrete pouring takes place directly on the construction site of the building (Figure 4) [1,2]. Figure 1: Scheme of ISOMAX system operation. 1—energy (solar) roof; 2—exhaust air from the interior; 3—reheating of hot water in an electric or gas hot water tank; 4—heat barrier in the outer walls; 5—drinking water supply to the building; 6—control unit; 7—supply ventilation air to the interior; 8—peripheral zone-ground heat storage; 9—ground heat storage (GHS); 10—cooling circuits; 11—central GHS; 12—combined distributor and collector of ventilation air; 13—thermal insulation GHS; 14—geothermal energy; 15—solar energy; 16—internal heat sources; 17—passive use of solar energy; 18—shelter for air conditioning equipment; 19— ventilation air extraction from the building; 20—fresh air intake for ventilation; 21—heat recovery–duct in the duct–recuperative ventilation [1, 2]. Figure 2: Passive cooling using registers of pipes located in the ground near the building underground at a depth of 1 to 2 m [1, 2]. Figure 4: Thermal barrier embedded in the load-bearing part of reinforced concrete panels bounded on the interior and exterior side by thermal insulation [1; 2]. Figure 3: A thermal barrier integrated into the building construction separates the load-bearing, static portion of the perimeter wall and the thermal insulation portion [1; 2]. The patented ISOMAX system uses pipe-in-pipe heat recovery ventilation that is both outside and beneath the building for building ventilation, as shown in Figure 6[1,2]. The ISOMAX control system is designed individually for each building (Figure 7)[1,2]. Figure 5: Schematic representation of thermal barrier walls [1,2].