With built and tested photovoltaic roof arrays, two passive houses in the outskirts of Sofia are becoming almost energy independent. Both houses were designed by Studio APXE and built under the leadership of the architectural studio, which is also the project manager during the construction process. The house in Kladnica, near Pernik, even upgrades the passive house standard to plus-energy.

Photovoltaic array including 12 panels with 3 kWp total power, Passive house in Lozen, Studio APXE

With the construction of 12 photovoltaic panels with 3 kWp total installed power, the house in the village of Lozen will produce about 29 kWh/m2 energy annually. This quantity will reduce nearly two thirds of the total energy demand for the household, which equals 53 kWh/m2 annually.

Passive House in Lozen
Technical equipment of photovoltaic system, Passive House in Lozen


Photovoltaic system including 50 panels with 12,25 kWp total power, Plus Energy House in Kladnica, Pernik, Studio APXE

The constructed photovoltaic system of the house in Kladnica consists of 50 panels with 12,25 kWp total installed power. The system will provide all the necessary energy needed for the building i.e. 38 kWh/m2 annually for all energy needs including heating and cooling, hot water, lighting and household appliances. The photovoltaic system works on the "back-up" principle. The 52 kWh/m2 annually generated energy is stored in batteries, as the surplus produced energy will be sold to the electricity company.

Besides all undoubted practical benefits of the system, the photovoltaic modules have an important contribution in forming the architectural character of the building as they fit almost imperceptibly onto the south roof of the passive house.

Plus Energy House in Kladnica
Photovoltaic system with storing of the surplus energy in batteries, Plus Energy House in Kladnica


Studio APXE