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Project

Villa Old Oaks Responds Passively

Credits: ©2010 Adapted from Ethel Baraona Pohl / Architecture Dai

Villa Old Oaks is a private residence located in a neighborhood of six larger villas in Ljubljana, Slovenia. The aim of the design was to open views from all main spaces of the house towards the existing common park with oaks over 100 years old. The building is constructed in half-floors, and in the heart of it is a stepped courtyard, onto which all the main spaces open. The building celebrates daylight conditions combined with efficient indoor and outdoor climate concepts. In Slovenia there are extreme climate conditions; with hot summers, when temperatures rise up to 35C and cold winter s when they drop below –10C or more, plus rain in spring and autumn. The client required an environmentally sustainable concept that would conserve energy and natural resources. He also desired an exterior space that would be usable in sunny and rainy conditions. The spaces of the house are therefore organized around a covered, exterior atrium; the combination of the atrium, the roof of the atrium, the house and existing trees around the house use sustainable strategies such as the alternating transparent and non-transparent ventilated membrane roof of the external atrium creates. In combination with the dense greenery of the surrounding trees, the atrium is cool in summer and provides rain protection, plus it provides outdoor privacy since it is protected against views of the neighbors. In winter, when trees are leafless, sun penetrates through transparent roof and atrium accumulates the energy and passes it inside the house. The sun also penetrates through glazed roof of the interior. The facades have pivoting wooden louvers that are computer operated to follow the course of the sun, controlling daylighting or darkening the working rooms and bedrooms completely. The atrium, semi-glazed roof and louvers allow major energy savings in lightning, cooling and heating. In addition, direct insolation via the facades and roof results in a high passive thermal yield during the heating period; In summer, effective sunshading helps to minimize cooling energy needs.

 

Villa Old Oaks Snow

In winter, when trees are leaf-less, sun penetrates through the transparent roof and atrium, accumulating the solar energy and passing it inside the house. ©2010 Tomaz Gregoric

The Project
To choose and architect for this project, the private client invited an architectural competition among five offices. OFIS Arkitekti, based in Ljubljana, Slovenia, was chosen.

The terrain slopes down towards the stand of oak trees. To guarantee that most of the major spaces would have access to this view, the house is organized in stepped levels following the terrain. The outline of the house keeps to the shape of the land, minus four meters all around, the minimum distance Slovenian law calls for vis-à-vis one’s neighbors.

The heart of the house is an external covered courtyard. Main spaces such as the entrance lobby and staircase, the children’s playroom, the dining, living, bedroom and work areas overlook this space. These rooms, plus the wellness area with its small pool, also have a view of the oak park.

The staircase roof is glazed. The courtyard roof is part-glass, part-wood and has views of the sky and the treetops, thus creating a strong link between inside and outside.

Structurally, the architects wanted to achieve a column-less ground floor. The ceiling of the dining and living area is slung from a Vierendeel beam hidden in the walls of the floors above. The glass construction and frames are also handled with minimal supports.

Other programs inside the house follow the client’s brief, which was very precise. His lifestyle includes working partly at home and having different hobbies. Security and fire escape issues are important, as is the clear division of private areas of the house and those where guests are allowed to wear shoes or where one receives the postman.

The house has also to be “intelligent”. Various functions such as air conditioning, security and sun-responsive external shade can be controlled by software, and different ambiences can be created using lights and music.

Sustainable Strategies
The house is a private residence positioned in the neighborhood of six larger villas. The site has a beautiful view to the existing common park with oaks more than 100 years old. Therefore the aim of the building was to open view from all main spaces of the house towards these trees.

The building is constructed in split levels. In the heart of the building there is a stepped courtyard, where all the main spaces open.

The building provides ideal daylight conditions combined with efficient indoor and outdoor climate strategies. In Slovenia there are extreme climate conditions; with hot summer, when temperatures rise up to 35C and cold winter when they drop below -10C or more. In addition there is rain in spring and autumn.

The client required an environmentally sustainable concept that would conserve energy and natural resources. Also he required an external space, that would be usable both on sunny and rainy days.

The spaces of the house are therefore organized around a covered, external atrium.

The combination of the atrium, the roof of the atrium, the house and existing trees around the house combine to create many sustainable features, including a half–transparent/half-opaque ventilated membrane roof on the external atrium that creates an airy rain-proof external space.

In combination with the dense greenery of the surrounding trees, the atrium is cool in summer and provides rain protection. One can enjoy outdoor privacy since the atrium is protected against views of the neighbors on both sunny and rainy days.

In winter, when trees are leaf-less sun penetrates through transparent roof and atrium accumulates the energy and passes it inside the house. The sun also penetrates through the partially glazed roof of the interior.

In addition the facades are combined with pivoting wooden louvers that provide protection against isolation and control ingress of day-light. On hot days the louver elements are computer-operated to follow the course of the sun. It is also possible to darken the working rooms and bedrooms completely.

The strategies used for the atrium, semi-glazed roof and louvers allow major energy savings for lightning, cooling and heating. In addition, direct isolation via the facades and roof results in a high passive thermal yield during the heating period. In contrast, during the summer effective sun shading helps to minimize cooling energy needs.

Relevant books:
The Solar House: Passive Heating and Cooling
Passive Solar House


Resources

OFIS Architekti (Ljubljana, Slovenia)