Heat waves, skyrocketing fuels… Heating or cooling a home is going to become more and more expensive and problematic, no matter where you are in the world.

In a few decades, parts of the earth that were used to temperate climates will experience much more extreme weather. The more heat, the more air conditioning, which will result in more energy consumption, which will contribute to global warming and translate into… more heat. A vicious circle in which we are already immersed and that condemns us to disaster.

There are, however, solutions to build buildings that have a lower environmental impact, either because they use recyclable natural materials, such as wood or mud, or because they follow a series of guidelines that drastically reduce energy consumption.

The latter is the concept of what are known as “passive houses”, which use the building’s own architecture to keep them warm in the cold months and cool in the hot ones, and which can reduce energy consumption by up to 90% .

Architecture that saves

“The idea is that saving energy should not only be a user thing, but rather it is something technical that can and should be solved with the components of the architecture and through technical knowledge,” explains Berthold Kaufmann, senior scientist at the BBC. Passivhaus Institut, the German institution that has established a construction standard that has now spread throughout the world.

In other words, reducing energy consumption should not only depend on lowering the thermostat, dressing up warmer in winter or getting used to being hot in summer: architecture should and can help.

By following a series of basic principles, such as good insulation and a study of solar orientation and surrounding climatic conditions, “passive houses” can reduce the energy footprint of a home to a minimum level.

The Spanish architect Nacho Cordero, who has been trained in the “passivhaus” concept, uses an analogy to explain it: “Imagine that you are going to build a boat, and the way to design it is to build a bilge pump so that it does not sink. Passive architecture is the opposite of this. It’s trying to make sure that the ship doesn’t need the bilge pump or that it only has it for an emergency.” Basically, he points out, the idea is simple, ” it’s trying to do things right “.

Although we usually associate ecological homes with spectacular and luxurious constructions, or those located in dreamy places, in reality any house, even a bland suburban apartment block , can become a passive house.

Of course, a building that meets their standards will be very different in Iceland or in Spain or Cuba . The concept and the physical properties on which it is based are maintained, but in a cold country, for example, it will try to capture the greatest possible solar gain, while where the sun is scorching in summer, it will seek to create shaded areas.


Passive architecture can be used for large public buildings like this fire station in Heidelberg, Germany.

The objective of all of them, however, is the same: to keep energy consumption to a minimum. “For new housing, the objective of passive houses is that they consume a maximum of 15 kW per m2 per year, and 25 for those that have been renovated with these standards,” says Kaufmann. Bearing in mind that a conventional home can consume between 150 and 300 kW per m2 per year, savings are significant .

Where does passive architecture come from?

Basically, passive architecture, understood as one that adapts to the climatic conditions of its surroundings, has existed since ancient times . The different peoples throughout history have tried to use the resources available in their environment and adapt to the geography and the weather to build houses that offer them an acceptable level of comfort.

The mud houses of Mali, cool inside under the inclement sun of the Sahara, or the igloos of the indigenous peoples of the arctic regions, are sustainable and passive dwellings.

With the invention of modern air conditioning and heating systems in the 20th century , however, architecture became largely disassociated from the climate around it. A building could be kept cool with an air conditioner despite being, for example, made of glass in a sunny region. Heating boilers, whether gas or oil, keep houses warm even with windows that don’t close properly.

However, the oil crisis of the 1970s put the concept of energy efficiency on the table, something that with the climate emergency has become a priority.

Since then, the concept of “passive housing” has become popular in architecture schools with the aim of reducing the energy impact of buildings. Although different schemes arise in the United States, Italy, or Switzerland, the one that has ended up prevailing is the one established at the end of the 1980s by the German Wolfgang Feist and the Swedish Bo Adamson. Its first “passivhaus” was built in 1991 . Today thousands of buildings around the world carry this certification.

What are its principles?

Five basic principles govern the passive house standard.

Thermal insulation . Passive houses have excellent thermal insulation, which can be triple that of conventional buildings. “In cold climates you need to use 20 or 30 centimeter layers of insulation, although in temperate climates it doesn’t need to be that thick,” explains Kaufmann. This protective layer that surrounds the house will prevent both the entry of cold or heat and its loss.

Air tightness. If quality insulation has been installed but not sealed well, heat will escape through the gaps and uncomfortable drafts will be created, losing energy efficiency. The “passivhaus” take into account the tightness of the buildings and, for this, tests are carried out in which air is blown into the houses to check where it comes out and be able to correct it.

Quality homes and doors. A very important part of the energy we use to heat a home escapes through the windows. Passive houses not only take maximum care of the orientation of the openings of the house to make the most of solar gains, but also use triple-glazed windows to avoid heat loss as much as possible.

Reduction of thermal bridges. They are those points where the insulating surface is broken (for example, by a nail or the frame of an aluminum window) and allow heat to escape into a building.

Ventilation system with heat recovery. When opening the windows to ventilate, heat is lost in winter and cool in summer. Passive houses have a mechanical ventilation system installed that filters the air and recovers the house’s own heat to heat the air that enters. With this system it is not necessary to open the windows.


The ventilation system with heat recovery allows for clean air without the need to open the windows.

Public regulation

This standard is increasingly common in regions of the world such as the European Union , where the institutions require that new constructions be as close as possible to almost zero energy consumption, guidelines that are then implemented in each country by its own regulations.

But, in general, more and more countries are trying to reduce the carbon footprint of new buildings. Sometimes even with striking measures, such as the one tried to impose by the mayor of New York, Bill de Blasio , who proposed to ban the construction of “the classic glass and steel skyscrapers, which are incredibly inefficient.”

The measure did not go ahead, but it did make many reflect on the relationship between architecture and climate change. For Kaufmann, de Blasio’s proposal makes a lot of sense: not only is it more ecological, it is also cheaper.

“30-50% glass area is more than enough to get the light you need. In an office building, for example, only the window area above the desks is useful , everything below it is not, it will be too hot in summer and heat will be lost there in winter”, he reflects.

Can I convert my home into a passive house?

Any house can become a “passive house. The most efficient will be those that have already been built with these standards, but” houses can be renovated following the passivhaus concept , “says Kaufmann.

“It is more common in the rehabilitation of entire buildings or single-family homes,” explains Cordero, although that does not mean that an apartment cannot be conditioned to get as close as possible to the “passivhaus” standard.

How much does a passive house cost?

Obviously, investing in quality materials makes the construction process more expensive . “It is true that it is a little more expensive, but not much more expensive,” acknowledges Kaufmann, who puts it at 5-6% more than the price of the building envelope. Other elements, such as higher quality windows, also add to the final price.

“In absolute numbers we calculate an extra 100 dollars per m2 of habitable area for a new construction, and a little more for renovations, about 150-200 dollars per m2,” explains the expert.

The architect Cordero recognizes that this type of construction raises the price of housing, especially if you want to get the certification offered by the Passivhaus Institute, a process that can be long. “It’s not mandatory, but in the end it’s a seal of quality ,” he explains.

Sealed or unsealed, the goal is the same: save energy. “Clients tell us that they want a house whose maintenance is not an energy drain . In the end it is common sense: if you are going to make a large investment such as building a house, it is preferable to spend a little more on building it but then , month by month, be more bearable”.

And the maintenance? Except for the ventilation system, which requires changing the filters periodically, the rest of the maintenance is the same as in conventional buildings.

In the end, Kaufmann explains, it’s about thinking ahead . Passive architecture requires such low energy consumption that it could be supplied only by renewable energies , something currently impossible for conventional buildings. “That’s why we need to reduce their energy demand, for when in the future we don’t have gas or other fossil sources of energy.”

A future that, perhaps, is not so far away.

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