Family house in Prague 6

A low-energy house in Prague 6 was created through a complete reconstruction and significant extension of a semi-detached house from the 1960s. The client purchased half of the house in very poor condition on a sloping plot with an interesting view of the northern part of Prague.
The task was to create a modern house with two apartments that would be maximally economical in technical and energy terms.

The problem with the plot was primarily the northern slope, which determined the arrangement of rooms and windows. Access to the plot and the entrance to the house, as well as the driveways to both garages, is from the north side, i.e., from below. From the south, the house is partially set into the slope and is shaded by mature trees and a nearby apartment building. The house opens primarily with its glazing into the more enclosed parts of the garden, facing the slope.

The original mass of the house – also due to the impossibility of intervening in the other half of the semi-detached house – was respected, and it was decided to maintain its shape and build upon it. Therefore, part of the extension was conceived as a kind of natural extension of the existing house to the west, in the same shape, form, and surface finish. A completely modern, simple cubic mass, one floor higher than the original house, was inserted between the original house and this end element, differentiated by both material and color, as well as by the format of the windows, etc.
This inserted mass is shape-wise simple, and the ventilated facade material – cement-bonded wood particle boards in a natural gray color – along with the possibility to completely cover the windows with external blinds in the color of the facade, gives it a stark character that contrasts with the white and relatively complex form of the original house.

In the original structure and half of the gray cube is the first apartment, designed for a universal client. This apartment has 3 floors and a roof terrace that is partially greened. The living room is atypically located on the first floor due to the sloping terrain and light access from the south, and it is lit by a walkable skylight in the center of the layout.
The second apartment, inhabited by the client, is designed in relation to the sloping terrain (which in this part of the plot was not leveled and built over with greenhouses and extensions to the original house). The layout thus responds to the slope, and the living room is located half a floor above the entrance part of the house and is 1.5 floors high. This creates a generous, well-lit space opening against the slope into the garden. Here, too, there is a roof terrace on the upper floor.

The main element of the interiors of both apartments are steel staircases. Each one is designed differently in terms of shape, but the formal concept is the same. They consist of white-painted staircases with a broken, slender stringer, complemented by distinctive railings made of horizontal profiles of strip steel. In the investor's apartment, this staircase visually appears to float above the first two flights, which are "heavy," and their railing is designed as a panel made of perforated sheet metal.

It is a masonry low-energy building with an estimated annual heat requirement of approximately 33 kWh/m²a. Heating is provided by a pellet boiler in combination with solar thermal panels and an integrated storage tank, and the heating bodies are convector units placed under French windows. Both apartments are equipped with controlled ventilation with heat recovery.