Konstantina Hristova, Ralica Tasheva , Pavel Vasilev, Andrey Pachilov

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Having the idea of ​​a house with minimized energy losses as a start point, we sought a relatively simple and comprehensive form, with minimal or no withdrawals from the volume in order not to destroy its integrity. Principally, in order to project a passive house, several are the forms to be considered as perfect. So when we talk about energy-efficiency it will not be wrong to assume the sphere to be the best one, as it has the least energy losses and is reckoned to be an ideal energy-efficient unit. But we should at the same time pay attention to the fact that an absolute sphere cannot be practically built.

As we give the compact form to contribute to the efficiency of the building and to be the main factor on the way to achieve passivity, we choose the sphere because of its clean lines and simple geometric form as well as for its perception of the surrounding area.

We use this basis and then add other methods to provide the necessary passive environment that brings comfort. The single family house is the only one of all buildings, which should become a home and a shelter for its residents, so that is the reason why our project combines high standards of comfort and aesthetic appearance while at the same time it covers high standards for energy efficiency.

We design the house, using part of a sphere, with center shifted above the terrain’s level in order to achieve two residential stories with the necessary rooms for living while preserving the required height for each of them.

The house is situated in the North-west part of the site, with a main entrance from the North, near the street regulation. This is made in order to achieve the most favorable positioning according to the geographical location and to provide maximum space for efficient yard during the summer and spring months for the residents. The yard is South-east with a pool and a summer kitchen with barbecue and seating. In the North-east part of the place we provide two parking places required for a four-person-family. There is a grid of alleys for accessing the building, as well as any other part of the yard.

The inner space of the building is organized around a central fireplace, which goes through both levels of the house and warms the surrounding rooms. The level-connecting stair is located concentrically as an interesting interior detail of the space.

Entrance area, toilet, closet, kitchen area, storage room, dining room, living room and an exit-door, situated in axis with the main entrance, to the court-yard area with a pool, are organized on the first floor /on the level of + 0.00 m./.

On the same floor, in a technical room behind the stair, is located the recuperation system, that refreshes the air and recovers the waste heat from the house. The recuperator heats the cold air from outside using exhausted air from the premises. In the project we select a recuperation system with 90% efficiency, compactness and minimum power consumption. The flow of fresh air is regulated depending on the specific needs. Also draws exhausted air from the kitchen and toilets.

Two bedrooms - one master and one for the children, two bathrooms - one accessible from the master bedroom and the other one from the atrium space above the living room are provided on the second floor /on the level of + 3.00 m./. The process of heating the rooms is related to the operating mode of the fireplace, as to the internal air, it is forced to circulate through the air- heating system.

The house itself is divided in four equal parts, in order to get four sectors with clear geographical directions, respectively North, South, East and West.

The South part of the sphere is the only one which is ‘opened’, we could call it ‘the glass wall’, it is equipped with appropriate profile system for passive houses with a coefficient of thermal conductivity U = 0.65 W/m2K. Photovoltaic panels are mounted on movable "shutters", used to transform solar energy for household needs as well as a sun-shadow device, working against the overheating of the house. They are situated in front of the glazing plane, above the facade’s surface. The panels take five of the building axes between the vertical arch bearing elements. The photovoltaic system itself, works properly no matter the weather – when the sun shines the production is with maximum quality and quantity, in cases of cloudy weather the amount of generated electricity is less, but relatively enough. The production of electricity depends on different factors - the major one is the location, that’s why we put the panels on the southern elevation of the building and suggest using a system, connected with the Earth movement around the Sun, and the different amount of sun-light in each single hour. Using such a system we provide the right angle of rotation of the solar panels and the highest amount natural sunlight for the needs of the house’s inhabitants. The purpose of this specified movement of the panels is self-shadowing to be avoided.

The East and the West parts of the sphere are completely closed. The walls are made of insulating panels attached to the wooden timber structure of the wall. A timber grid, bearing the external cladding, made of wooden shingles, is placed above the panels.

The entrance finds place within the North part. The front door is inside the building volume. In order to be protected from wind, rain, and other climatic conditions it is covered with a draft-stop made of glass. It is situated out of the building volume, considering form requirements /an igloo resemblance was searched/. It plays as an attempt to mark the entrance area of ​​the building.

The external and internal cladding, the bearing building construction and the wall structures are made of plywood in order to use local, traditional materials and having minimal energy losses because of the lower coefficient of thermal conductivity of the wood, used as a building material. The result of using only one material for inner and outer spaces, as well as bearing structures is a perfectly unite and homogeneous building envelope, adequate to the natural environment. The construction of the spherical body is a wooden structure of curved bearing elements, bent in the shape of the sphere, and transverse horizontal wooden rings, between them, providing the stiffness of the building. The second floor is hooked by steel ropes, attached to the upper timber belt. The entire wooden structure stands on a reinforced concrete slab, foundated according to the relevant seismic requirements. Compared to the overall volume of the building minimal glazing is planned, which provides the necessary sun-light quantity and reduces heat losses.