In the search for models capable of economising resources, Hybrid Buildings, especially those with residential uses, are chance samples that include the gene of mixed-use development in its code. This gene is necessary in order to adapt to the signs of the times. Nevertheless, this mixed condition makes them mistakenly similar to another avant-garde model, a model that at first sight seems to be its predecessor when in fact it is the complete opposite. We are referring to the Social Condenser.

In the first study done on hybrids, Joseph Fenton states that they came about in the first quarter of the 20th century, in order to revitalise American cities and make optimum use of land.
Simultaneously, the constructivist movement brought about the social condenser. It was described by Moisei Ginzburg   as a building designed to transform relationships among citizens in the three areas of the new socialist state: collective housing, clubs and factories.
Both are the fruit of the avant-garde era, when historical events provided a clean slate for many new approaches. The condenser was developed in the recently created Soviet Union, where there was total land availability and the need for housing was urgent.
This was an opportunity for expirimentation that the constructivist architects of the OSA (Union of Contemporary Architects) took full advantage of. In the competition for new residential proposals, organised in 1927 by the group’s journal, Sovremmennaya Arkhitektura, duplex and triplex housing, interior streets and entrance galleries appeared in projects. Ginzburg developed some of these proposals, crystallised in the minimum living cell (27-30 m2), which made up large residential blocks called dom-komuna. They would serve to house the proletarian masses and aimed to influence the social behaviour of its inhabitants. Most of the activities which previously were part of private life, took place in common kitchens, canteens, launderettes or nurseries.

For the first time, the design of circulation considered human fluxes to be an opportunity for events and socialisation. The collectivisation of most domestic functions encouraged women to become part of public life, at the expense of, among other collateral effects, having to endure mutual surveillance and increased control. Reducing privacy in the bedroom effectively helped to get rid of bourgeouis conventionalism.
The social condenser was born of the State, while the hybrid is the offspring of the capitalist system. It is the commercial result of a sum of private interests and subtraction of urban determiners. Speculation and profitability were its parents and the American city was its kindergarten. While the condenser was the manifestation of an ideology, even a homage to architecture , the history of the hybrid was written in accounting books.
On the one hand, the young Soviet state was teeming with experimentation. Modern European architects were affected by this and inserted it into a less inflamed discourse and presented it at the CIAM congresses. On the other hand, land prices spurred the initiative of investors. Europe ignored the development of the American city, where ideology was not part of the programme.
The condenser was the result of functional thinking, which was the guiding light of the constructivist method: “a method indicating with determination which path to follow, and suggesting a solution to the architect’s problems, taking into account the premises he is confronted to”. The hybrid was also the result of functional thinking but on a scale where user flux was just as important as economic flux. While the condenser concentrated all of its transformation capacity on the members of a closed community, –the inhabitants of communal housing, club members, factory workers– the hybrid opened up to the city and encouraged contact among strangers, intensified land use, densifying relationships and left room for indetermination, as opposed to the control that the condenser imposed.
As far as relationships are concerned, in the hybrid they are established outside of the domestic area, while in the condenser, they go into the private realm up to the bedroom door.

So why is there that misunderstanding nowadays between hybrid and condenser? Hybrids are characterised by a mix of uses in the same project. It integrates different programmes which also have different developers, different management and, obviously, different users. This is to say that a hybrid can be as diverse as a city in users, use times and programme.
On the other hand, condensers –developed until the 1980s due to the influence that constructivists had on Le Corbusier and his followers –were mostly buildings with minimum housing where, because of economic and ideological reasons, a series of functions of private life were segregated and converted into public functions. The machine-like vision of housing facilitated the separation of functions as productive processes. Just as productive processes become cheaper as space is maximised, systemisation and compression of vital functions are result in savings for the developer, in this case the State.
The programmatic features of these prototypes, capable of housing over 1,000 inhabitants, spreads out over floor and section with the variety of a small city. The same functions that can be found in a hybrid can be found here, especially in Unités and those that followed, where businesses and even offices were inserted on the so-called inner street. Nevertheless, the difference rests in the fact that each function is thought out not to create intensity and vitality in the city, nor to attract flux of outside users or even to favour mixing and indetermination, but to achieve a self-sufficient and  ‘complete’  building that can isolate itself from the conventional city.
This means that the presence of various subordinate functions on floor and section does not make a housing building a hybrid. Along the same lines, a facilities building that includes a varied public use programme would not be a hybrid, but a modern version of the social condenser, as a club type. Hybridisation is not only in the programme but in initiative, investment and management.

During his delirious route along New York history, Rem Koolhaas, a devoted follower of the constructivists, stops at the Downtown Athletic Club and describes it as a building where the social condenser’s powers of transformation succeeded for the first time.
He does not refer to the communal housing version, but the workers’ club typology.
The high-rise programme of a building dedicated to leisure and physical fitness, where financial district singles went to ‘to reach new strata of maturity by transforming themselves into new beings’ seemed to him to be the culmination of tests done by Leonidov in the 1920s, differing in that the Downtown Athletic Club did not need Stalin’s approval and thus could be built.
It is symptomatic that he stops at this building and compare it to a condenser because, if we pay attention to Fenton, this building is a hybrid because it is made up of a sports club on lower floors, a hotel on upper floors and a restaurant in the middle, for users of both programmes. However, the fact that from one reality such different analyses can be extracted is symptomatic of the potential that those first hybrids held and that the segregation of uses, following the Athens Charter, pushed into obscurity for decades.
The American hybrid was fatally wounded after World War II. Its contemporary, the condenser, had succumbed much earlier, not only in its club version, considered by Stalinists to be too elitist, but also in its domestic version. The dom-komuna were rejected by their own inhabitants, desiring more privacy, and by their managers, who showed that with the technology of the day, they were unmanageable structures.

Nevertheless, these two visions of the world, represented in antagonistic models, the fruit of ideology as opposed to the fruit of money, have continued to reincarnate, whether more or less intensely, up to current times. Throughout the past 80 years, condensers have gone through some defeats, most of them due to the desire to programme and enclose the lives of its users The Corviale or Park Hill cases were the most painful for the model’s defenders. Meanwhile, hybrids have had a time of mutation on the hybrid block to attract investment and facilitate management, with results like the Barbican or Ihme Zentrum, along with other important examples. A selection of both is included in the comparative analysis that follows this text.
In the last ten years, the balance of models to be followed seemed to favour the hybrid. After the theoretic recovery in the 1980s, where we have examples in Steven Holl’s work  and the work of Ábalos & Herreros, among others, it reappeared at the beginning of the 21st century, again as a saviour to American cities through projects such as the Museum Plaza. Devoid of ideology and endowed with great versatility, the hybrid is also finding its place in Europe, not to mention Asia, where the mixing of uses has been inherent in the development of its cities.
The hybrid may possibly have exhausted the power of its antagonist to model human conduct, though not in the way Russian idealists had thought. It may also have added its natural capacity to activate the city. Its vigour as a hybrid favours it in times of crisis, though it does have an Achilles’ heel called financing. It is not a disciplinary prototype, but a concentration of interests. It is not based on tradition but on the future. Its survival depends on consensus. Being confused with a social condenser is really the least of its concerns.