Sustainable hospital architecture

Clément Billaquois, Franck Courari, Hugo Viellard, Garcie de Navailles

Introduction : issues and limits

The healthcare sector plays a major role in carbon emissions. In france, it accounts for around 34 Mt CO2e, or 6.9% of the country’s carbon footprint (1). this figures varies from 4% to 8% in OECD countries.

The Shift Project (2) proposes breaking down emissions from the healthcare sector into three scopes. 1

If we look more specifically at the carbon footprint of a hospital project, we need to distinguish between greenhouse gas (GHG) emissions linked to construction, which are accounted for in the building sector, and those linked to the operation and running of the building, which are accounted for in the healthcare sector.
Architectural arrangements obviously have an impact on the former (construction), but also on the latter (operation and functioning) within the limits of scopes 1 (direct emissions) and 2 (indirect emissions linked to energy).

This preamble clarifies the limits of the approach taken by the architect, since Scope 3 emissions generally account for the majority of hospitals’ carbon footprints (Scopes 1 and 2 represent only 16% of the total carbon footprint), while being much more difficult to quantify. 2

So, while it is necessary to seek to reduce scopes 1 and 2, it is also imperative to take a more global view of a hospital’s carbon impact as a whole in order to act on scope 3 as well (the question of the hospital’s location and accessibility by public transport, for example, is crucial to reducing the cost of employees’ home-to-work journeys).

The hospital is a complex building, the result of a synthesis of contradictory issues:

  • Functionnal issues (related to quality of use, internal and external flows, distances travelled, etc.) ;
  • Technical issues (related to the use of complex and cumbersome equipments, the presence of a large number of different networks such as heating, ventilation, smoke extraction, high current, low current, medical fluids, etc.) ;
  • Urban issues (related to the position and often large size of the project) ;
  • Regulatory issues (related to fire safety hygiene, insurance and construction method) ;
  • Architectural issues (related to spatial quality, as hospitals being above all a place of reception) ;
  • Economic issues.

It is undoubtedly because of this complexity that the new environmental standards (RE2020) are still not applicable for hospitals while they exist for other buildings (housing, offices, etc.).
In this respect, it should be noted that the future RE2020 approach, with the application of the environmental regulatory decree of 10 April 2017 concerning all new constructions of public buildings, will in particular take into account carbon-related issues, which have and will have a strong impact on hospital building projects, both in terms of the materials used for construction and the nature of the technical systems implemented.

A hospital construction project can act on several elements to limit its carbon impact. The design of the project has a direct impact on :

  • The project’s future energy consumption ;
  • CO2 emissions and the possibility of achieving low-carbon architecture ;
  • The future operation of the building and its ability to tolerate change to guard against the risk of obsolescence. After all, the best way to save CO2 is not to build at all !

We are proposing a number of approaches that we are implementing in our projects to respond to these issues of consumption, construction and resilience.

  1. Energy consumtion issues

Hospitals are, by their very nature, large consumers of energy. They operate 24 hours a day, 7 days a week.
Hygienic conditions require a high level of air renewal, which has an impact both on electricity consumption, since air handling units are in constant operation, and on heat loss due to the evacuation of indoor air, which increases the need for heating or cooling depending on the season (up to 10 volumes / h in operating theatres).

Some processes require a great deal of heat (sterilisation, kitchens, etc.) and generate a higher energy requirement for cooling than for heating.
In fact, producing one frigorie (i.e. cooling by 1 degree) requires twice as much energy as producing one calorie. However, in a context of global warming, this intrinsically leads to an increase in energy consumption because of cold needs.
So that the consumption of a hospital is 250 kWh/m²/year while it is only 50 kWh/m²/year for new housing.

There is little room for manoeuvre when it comes to these consumption issues, except to change hygiene standards and accept higher or lower temperatures in the premises, which is not done in the specifications that architects receive for the construction of their projects.

The main technical levers we use are as follows :

  • « Bioclimatic » design of facades (limits solar inputs in summer and maximize them in winter) and high-performance thermal insulation (reducing heating and cooling), see the Nord Franche-Comté Hospital project developed below ;
  • Recovery of so-called “fatal” energy (3) ;
  • Connection to a heating network, geothermal energy, solar panels (renewable energy production) ;
  • Systematic double-flow ventilation of the premises with high-efficiency recuperator and low-consumption motor, variable-speed low-consumption secondary pumps, and ducts and pipes with high-insulation lagging (to limit heat loss).

All these principles mean that the initial investment costs are higher than for a standard building: better insulation is more expensive, and bioclimatic facade systems such as adjustable brise-soleils cost more than a simple roller shutter. Installing energy recovery systems, such as high-efficiency or low-consumption equipment, also represents a higher investment. However, a lifecycle analysis can help to weigh up the return on investment against the initial extra cost.

Bioclimatic envelope: example of the Nord Franche-Comté hospital
The new Nord Franche-Comté hospital, a merger of the Belfort and Montbéliard hospitals 3, is locating on a slope of 25 hectares of the town of Trévenans. The project is located at the top of the site, stretching out along the contour lines to form an elongated volume 210 m long and 98 m wide. It takes advantage of the slope of the natural terrain to separate the flow of traffic (the emergency access road at the top and the public forecourt at the bottom) and give the hospital wards far-reaching views over the landscape to the edge of the Vosges forest.

The project combines two ambitions for the hospital: that of a rational and progressive “care machine”, and of a living place driven by a concern for the well-being of both patients and staff. Thus, the reassuring presence of wood is found both on the facade (protected between two panels of breathable glass) and in the interior spaces, particularly in the hallway punctuated by atriums which open generously onto the patios, blurring the boundaries between inside and outside. 4

The building develops strip facades: each facade frame has a 45cm spandrel window, with a width of 125cm anda height of 200cm. The facades are as efficient as possible: they are insulated from the outside and “breathable”. 5 In addition, the use of glass gives great durability to this ensemble.
The transparent glazing and low spandrel height (45cm) offer the lying-down patients a panoramic view of the landscape outside. 6

  1. Low-carbon construction

The origin of building materials and their nature play a major role in the carbon impact of the act of building. This means trying to reduce resource consumption as much as possible.

Firstly, the construction of a hospital building often takes place on a established site. It is then possible, if the project owner wishes, to demolish as little as possible and avoid all temporary constructions and bypasses, which generate additional costs and waste.

Particular attention should then be paid to the facade materials, which should be chosen for their durability.
For instance, glass is an inalterable material that requires no maintenance, but with a strong carbon impact (like all materials that require firing). It must therefore be used in the right place according to the client’s budget.

Some materials, such as solid stone, are extremely durable and have a limited carbon impact (in fact, the carbon impact of stone is almost zero: you literally move a piece of inert soil to another location, the only emissions being those related to transport). However, they represent a high cost which must be anticipated.

But it is also possible to use bio-sourced materials such as hemp to create facades made of hempcrete and wood frames. However, these techniques are difficult to implement because they are outside the regulatory and normative framework. Indeed, there is not necessarily unified technical documents or technical advices for these relatively new construction methods.

Then, for interiors, we can try to use as many virtuous, local or recycled products as possible and limit their quantity:

  • We can do without interior finishes and leave as much as possible the raw supports: wood, concrete to limit the quantities of paint and false ceilings. However, this is not always possible for reasons of hygiene or sustainability ;
  • It is possible to make lightweight partitions using cellulose fibre, mineral fibre or gypsum board (30% cellulose) rather than plasterboard, but at three times the cost ;
  • Concrete elements can be made of 60% recycled concrete (use of recycled slag or ash in the cement formulation) ;
  • Concrete can also be “local” depending on the location of the project (less than 50 km from the site for aggregates and cement).

Hygiene is often the main imperative when designing a hospital. It must be easily cleaned to prevent the spread of germs, but also limit the number of different cleaning procedures to reduce maintenance costs.
The use of eco-friendly biobased materials is often complex.
Exposed wood is almost forbidden in the premises that need to be cleaned regularly. It can’t be used in floors, siding, or furniture… where it is often replaced by PVC or laminate.

PVC (from the petrochemical industry), which is used in most hospitals, could be replaced by tile or rubber floors. However, the cost is higher, and performance is not always equivalent (UPEC classification).

Building a hospital using a wooden structure is also very complex: the bulkiness of the beams in the false ceilings implies increasing the height of the buildings and therefore the cost, and fire stability requires either complex discussions with the fire safety services, or encasing the wooden structures in plaster (again generating a significant extra cost, in addition to using the material in a less than virtuous way).

Biobased materials can then be found in invisible spaces: plant wool for acoustic and thermal insulation, false ceilings made from plant fibres, but always at a higher cost and rarely compatible with the project owner’s budget.

  1. A resilient architecture

We see that the new hospitals that are being built today are expected to replace hospitals built in the 1970s or even 1980s. This is the case for hospitals of Tours, Caen, Cannes, Chambéry, Rennes, Bichat (Paris) and Beaujon (Clichy), etc.
Sometimes barely fifty years after their construction.

This is mainly due to :

  • The acceleration of medical and techniques progress (the appearance of new machines, new methods leading to a new spatial and technical paradigm) ;
  • The creation of new disciplines ;
  • The reduction of hospitalization in favor of the technical facilities  ;
  • Changes in fire, environmental and other standards ;
  • Premature wear on buildings used 24/7.

These developments make buildings obsolete and difficult to reuse. They often end up demolished.
Based on these observations, we believe that our duty as architects in terms of ecology, when designing a hospital, is to ensure that it can last as long as possible.
Doubling the lifespan of hospitals would limit the consumption of resources during its construction (agricultural land, materials, energy, etc.).

To hope for a longer lifespan, architects must strive to learn the lessons of their predecessors and design a building that will withstand both medical and normative developments.

In our practice, we have implemented a series of rules that help us to create hospitals capable of postponing their obsolescence as far as possible :

  1. Compact shade ;
  2. Neutral frame ;
  3. Scalable structure / Flexibility ;
  4. Uniform floor height / Isotropy.

And even imagine, from its construction, what the building could become when it is no longer a hospital.

Compactness :
Medicine evolves much faster than architecture. Hospital projects develop over many years, sometimes up to a decade or more.
With this in mind, and to tackle the obsolescence of buildings, in 2000 the Brunet Saunier & Associés pratice developed the “monospace”, a simple and rational typology that allows great flexibility in the organisation of hospital functions. 7
The monospace is not a type in itself. It provides a response to programmatic instability by offering a regular, reversible spatial arrangement, making it possible to develop large, continuous floors, all benefiting from a constant thickness and a very strong access to light.
Like fractal geometries, this compact shape has a highly developed linear facade: like a Menger sponge, the surface area in contact with the outside is multiplied. 8
This simple and rational morphology or structure allows each of the parts that compose it to expand or compress without upsetting the balance of the whole.
The monospace is more a environment than a form. It is a continuous space and neutralized by the reduction to the essentials and the unitary distribution of differentiating and orientating elements.
The different departments of a hospital, heterogeneous in their functions as their dimensions, are thus contained within a simple, unitary form, an intelligible prism, whose apparent simplicity testifies to the great mastery of the project’s complexity. Contrary to appearances, it is indeed very difficult to obtain a simple shape that accommodates all the functions yet so heterogeneous.
In addition, the compactness and simplicity of the shape meet another optimum: that of the shape coefficient of the building (4) (i.e. the ratio of the total envelope area to the habitable volume of a building. This coefficient depends directly on the shape of the building, and gives a direct indicator of possible losses and therefore energy consumption).
The singular compactness of this morphology works to bring services closer to each other, to reduce distances to travel, to promote synergies and collaborations.
This homogeneous shape is designed to be future-proof. On the contrary, it anticipates the constant evolution of hospital practices by not subjecting the building’s appearance to the functions it houses, which are likely to change rapidly.
Thus the simple and unified shape guarantees both the functional quality and the thermal performance of the building.

Neutral frame :
In our projects, we propose the implementation of a neutral frame in all directions.
The neutrality of the plan is characterized by a rigorous network which is based on a homogeneous grid serving as a guide to the installation of the posts. The project is thus designed as a stratification of homogeneous platforms where the impact of the load-bearing points is trivialized by the regularity of their implementation.
Within this grid, all substitutions are possible, both during the design phase and after the commissioning of the building.
It hosts technical platforms and accommodation without distinction. All services, whether modular or local, can be accommodated. 9
This regular device limits the number of load-bearing points and avoids any rigidity linked to structural walls in plan. The framework provides a simple and intelligible answer to a complex problem. It allows to implement along the hospital circulation all the different sizes of premises that can be found in a construction program : 8, 12, 18, 24, 36 m² and so on…

Flexibility :
These platforms are then regularly pierced by large courtyards 15m wide by 15 to 20m long, which allow light to penetrate to the heart of the plan. In this way, the built thickness remains constant and natural light is always guaranteed. 10
Although it appears particularly orderly, the regulating principle is nonetheless plastic. Organised along an axis (general circulation and points of ascent), the figure is not closed.
It can still be extended, enlarged and transformed, while maintening its internal consistency.
Between each courtyard/patio, the project allows the implementation of modules which can be combined with each other to create larger services : this is often the case for large services such as operating theatres, pharmacy or dialysis, which extend over several modules and loop around each other along the patios. 11, 12, 13
Finally, patios can be considered as potential extensions. We can occasionally densify them, build a terrace or fill in a loggia.

Isotropy :
To be infinitely reconfigurable, the building is not the formal translation of a particular functional need, but a system, a form without composition, without score.
This research leads to design facades that are also scalable, and as generous as possible. The implementation of homogeneous facades, with the same rhythm of openings and continuity on each floor and around the entire perimeter of the building, allows each linear metre of facade to have a window, without any solid part encumbering the scalability of the premises.
So made, facades are isotropic : they have the same characteristics in all directions.
This choice makes it possible to deal with all sunlight situations by using external, adjustable solar protection.
The large proportion of glass surface area means a very high luminous autonomy, reducing electricity consumption.
Finally, as far as possible, the height of the floors should be the same everywhere. It is then possible to perform program substitutions between them and at all levels.

In conclusion

The example of the Saint-Ouen Grand Paris Nord Uniervsity Hospital: a resilient architecture

The Saint-Ouen Grand Paris Nord University Hospital, 21st Century Health icon, is a state-of-the-art medical infrastructure, both human and efficient, ideally designed to meet the growing needs of the Paris metropolis in the coming decades. 14, 15, 16
Generously open to the city, the hospital has a clear, identifiable volume which stands as a landmark in the urban space. Its accessibility is enhanced by a reduced footprint. The compact hospital donates to the city large planted areas, an urban forest and a wide mineral forecourt.

Ces grands jardins, plantés à la fois au sol et sur le toit, participent à réduire l’effet d’îlot de chaleur. Ils permettent aussi une meilleure gestion des eaux de pluie. Ces jardins témoignent ainsi de préoccupations contemporaines environnementales, tout en affichant une image résolument tournée vers la préservation de la biodiversité. Ces jardins sont le symbole d’une institution qui place l’humain au centre, et fait du bien-être des patients sa priorité, reprenant à son compte l’aphorisme latin « Medicus curat, natura sanat » (le médecin soigne mais c’est la nature qui guérit).
L’espace public se prolonge jusqu’à son seuil, offrant une respiration dans le tissu urbain, des lieux de rencontre, d’échange et de calme. Largement vitré, l’hôpital s’ouvre aussi par sa transparence et les liens visuels qu’il tisse entre extérieur et intérieur. La présence végétale à différentes échelles et à tous les niveaux du bâtiment participe, outre son rôle curatif indéniable, à faire de ce lieu un havre de sérénité. Cette proximité visuelle et physique avec une flore abondante, la possibilité de suivre la course du soleil et celle des saisons, offre aux résidents de l’hôpital une formidable allégorie du processus de guérison. Ce cadre de résidence, de travail, ou de simple visite, place le bien-être au centre de l’expérience du soin.

La toiture de l’hôpital est un monde à part. Planté de nombreuses espèces végétales et protégé des nuisances de la rue, le jardin qu’elle accueille est un refuge ouvert à tous, soignants, visiteurs et citadins. Accessible depuis l’hôpital comme depuis la ville, il est un promontoire qui surplombe les bâtiments alentours et procure une vue large et dégagée vers un horizon lointain. Voir loin, au-delà de l’hôpital, c’est en effet regarder au-delà de notre environnement immédiat, penser à l’avenir, et oublier le temps d’une promenade ou d’un déjeuner, un quotidien parfois difficile. Ses proportions, similaires à celles du Jardin du Palais Royal de Paris, et son caractère public confèrent au jardin sa dimension remarquable. Aérienne et végétale, la toiture devient alors un lieu d’abstraction, de répit, une échappatoire.

L’hôpital ouvert et urbain est aussi une exigeante machine à soigner, à la hauteur des niveaux de performance, d’adaptabilité et d’efficience auquel elle s’adresse. La technologie qui sous-tend sa conception joue un rôle capital dans sa faculté à répondre aux enjeux sanitaires d’aujourd’hui et de demain. La superposition de plateaux équipés, neutres, réversibles et abondamment éclairés de lumière naturelle, permet une organisation spatiale souple et évolutive des services.

Cette conception radicale écarte tout artifice non essentiel et concentre ses efforts sur la capacité d’adaptation de l’équipement de santé, en temps réel comme à long terme. Ainsi préparé, l’Hôpital Universitaire Saint-Ouen Grand Paris-Nord devient un outil fiable aux mains des personnels soignants pour assurer la prise en charge bienveillante et sereine des patients.

Construire un hôpital aujourd’hui consiste à concrétiser le changement, et l’Hôpital Universitaire Saint-Ouen Grand Paris-Nord en est le lieu emblématique. Les effectifs, les patients et leur état, les techniques et les besoins évoluent en permanence. Le mouvement et l’imprévu sont les seuls invariants à prendre en compte. Conçu pour pérenniser l’inconstant, l’Hôpital Universitaire Saint-Ouen Grand Paris-Nord arbore la flexibilité comme une philosophie en s’inscrivant durablement dans la ville sans ne jamais cesser de muter ni de s’adapter.