Vienna is by no means the most crowded metropolis in the world, or even in Europe. Even so, Caramel Architects has designed a house on the outskirts of the city that provides a model for getting more people into a smaller area without giving up amenities like natural light and private garden space.

It is widely estimated that 70 percent of the world’s population will be living in cities by 2050. So questions are being asked about where to put all of those new residents. To many urban planners, the answer lies in tower blocks. The CJ5 house designed by Austrian practice Caramel Architects offers a different solution.

The prototype has a lower floor-area ratio (the proportion of usable living space to the overall property area) than most of the standard housing types in its Vienna district. This means that more of the site is used for livable functions and there is less waste. Caramel achieved this maximal usage by employing a narrower plan (5 x 35 m/16 x 115 ft) and by assigning all of the available space. For example, the wide open stair contains the kitchen and dining furniture.

But the house is not purely about shoe-horning life into small boxes. The CJ5 is a 3-story house of 170 sq m (1,829 sq ft) that achieves a high-quality living environment with spaces that flow into one another. The horizontal and vertical open plan allows the interior to feel much larger than its footprint. The living area extends through the courtyard, expanding the area for relaxing or entertaining, and a terrace on the upper floor makes the modest interior space feel much more luxurious.

The tall, narrow structure also maximizes natural light. Wrapped in white concrete, the house has a sculptural presence, as it is not currently surrounded on all sides by other buildings, and it appears to be dense and solid. But inside the spaces receive ample sunlight through windows on the entrance façade, through large light wells and from the wide courtyard opening.

The plan for the CJ5 includes all of the features expected of a modern home, as well as a garage and cinema room, and the open-air courtyard/garden space at the center that defies all the bleaker notions that the word "density" usually inspires. All of the functions work around and through the courtyard. And no space is left vacant.

Attention to materials also makes this house a more attractive option than the spatial measure might suggest. Textured formwork concrete walls and oak flooring are used throughout. This continuity of materials also helps to make the interior feel like a large open area that branches into different zones, rather than a series of small articulated spaces.

This prototype has been designed with a single bedroom and an extra "atelier" space that can be used for sleeping,too. The garage can also be used as a studio space, as the current resident is an artist. Since the CJ5 is intended to be a model that can be replicated, the structure has been designed to be part of a series of such homes. The house is contained in a three-sided firewall, which allows for further houses to be built right up against it.

The CJ5 is almost completely energy independent, the architects say. It derives its own power supply from photovoltaic panels located on the south-facing section of the roof, and it uses an air-to-water heat pump, which converts energy stored in the outside air for use in heating and hot water. It has also been constructed with high insulation values.

While this is no doubt an attractive, livable house, the question still remains how such a model might replace multi-story apartment blocks, especially when faced with the numbers of families who will need at least two or three bedrooms. But the idea of condensing space while upping design quality is certainly a sign of thinking in the right direction.

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