Vasil Sharlanov Dipl. Arch, Desislava Chakarova Dipl. Arch.

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The passive house is situated in Lozen near Sofia, Bulgaria. It is designed in a compact, simple shape in order to be more affordable and more energy efficient. There is no basement, which would have been more expensive and difficult to insulate. The main living areas are placed in the southern part of the house. Since the predominant cold wind in Bulgaria is coming from the northwest, all the secondary rooms in the house are situated in that area and serve as an additional barrier.
This functional segregation is also observed from the outside. The two main volumes of the house are differentiated in white plaster for the secondary rooms, and in wooden cladding for the main living area. Movable solar louvers provide shading in the summer, since it could get quite hot in Bulgaria. They also serve as an aesthetic element on the southern façade.

The following diagrams explain the design approach in short:

Structure and Materials

The most popular and traditional construction nowadays in Bulgaria is the cast-in-place reinforced concrete structure, and that is why, it is used in the house. It has also proven to be effective in case of an earthquake and the site is actually in a seismic area. The wall materials include bricks, another typical material for Bulgaria, and a lot of insulation in order to cover the passive house standard for annual heating and cooling. The insulation for the walls is high quality mineral wool, while rigid insulation is used for the roof and for the foundation slab. The windows are triple-glazed, passive house certified, and have a U-value of 0,65 W/m2K.


The house uses highly efficient heat exchange ventilation system, which main unit is stored in the mechanical room on the first floor. All the electrical appliances in the house are with a high energy efficiency class. On the top of the house can be installed optional photovoltaic solar panels, which can make the building a zero-energy house. Vacuum tube solar panels for heating water can also be place on the roof.