In just a few decades, parts of the world accustomed to temperate climates will experience far more extreme weather. More heat means more air conditioning, which will result in increased energy consumption, contributing to global warming and ultimately leading to… more heat. A vicious cycle we are already caught in, one that condemns us to disaster.
However, there are solutions for building buildings that have a lower environmental impact, either because they use recyclable natural materials, such as wood or clay, 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 warm months, and which can reduce energy consumption by up to 90%.
"The idea is that energy saving should not only be the user's responsibility, but is a technical matter that can and should be resolved with the components of the architecture and through technical knowledge," Berthold Kaufmann, senior scientist at the Passivhaus Institut, the German institution that has set a construction standard that has now spread throughout the world, explains to BBC Mundo.
In other words, reducing energy consumption shouldn't just depend on lowering the thermostat, bundling up in winter, or getting used to the heat in summer: architecture can and should help.
By following a series of basic principles, such as good insulation and a study of solar orientation and the climatic conditions of the environment, "passive houses" can reduce the energy footprint of a home to a minimum level.
Spanish architect Nacho Cordero, who trained in the "passive house" concept, uses an analogy to explain it: "Imagine you're going to build a boat, and the design approach is to include a bilge pump to prevent it from sinking. Passive architecture is the opposite of this. It's about trying to ensure the boat doesn't need the bilge pump, or only uses it in emergencies." Ultimately, he points out, the idea is simple: "It's about trying to do things right.".
Although we usually associate ecological homes with spectacular and luxurious constructions, or those located in dreamlike settings, in reality any house, even a bland suburban apartment block, can become a passive house.
However, a building that meets these standards will be very different in Iceland, Spain, or Cuba. The concept and the physical properties on which it is based remain the same, but in a cold country, for example, it will try to capture as much solar gain as possible, while where the sun is scorching in summer, the aim will be to create shaded areas.
Passive architecture can be used for large public buildings like this fire station in Heidelberg, Germany. GETTY IMAGES.
The goal of all of them, however, is the same: to keep energy consumption to a minimum. "For new construction, the target for passive houses is a maximum consumption of 15 kWh per square meter per year, and 25 kWh for those renovated to these standards," says Kaufmann. Considering that a conventional home can consume between 150 and 300 kWh per square meter per year, the savings are significant.
Where does passive architecture come from?
In essence, passive architecture, understood as architecture that adapts to the climatic conditions of its environment, has existed since antiquity. Throughout history, different peoples have attempted to utilize the resources available in their surroundings and adapt to the geography and weather to build dwellings that offered them an acceptable level of comfort.
The mud houses of Mali, cool inside under the harsh Saharan sun, or the igloos of the indigenous peoples of the Arctic regions, are sustainable and passive dwellings.
New passive house in Asturias, Spain. DUQUEYZAMORA.
With the invention of modern air conditioning and heating systems in the 20th century, however, architecture became largely detached from the surrounding climate. A building could be kept cool with an air conditioner even if it was, for example, made of glass in a sunny region. Heating boilers, whether gas or oil-fired, allow houses to be kept warm even with poorly sealed windows.
The oil crisis of the 1970s, however, brought the concept of energy efficiency to the forefront, something that has become a priority with the climate emergency.
Since then, the concept of "passive house" has gained popularity in architecture schools with the aim of reducing the energy impact of buildings. Although different schemes emerged in the United States, Italy, and Switzerland, the one that has ultimately prevailed is the one established in the late 1980s by German Wolfgang Feist and Swede Bo Adamson. Their first "passive house" was built in 1991. Today, thousands of buildings worldwide hold 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 up to three times that of conventional buildings. "In cold climates, it's necessary to use insulation layers of 20 or 30 centimeters, although in temperate climates they don't need to be so thick," explains Kaufmann. This protective layer that envelops the house will prevent both the entry of cold or heat and its loss.
Airtightness. If quality thermal insulation has been installed but not properly sealed, heat will escape through the gaps, creating uncomfortable drafts and reducing energy efficiency. Passive Houses prioritize airtightness, and to ensure this, tests are conducted in which air is forced into the houses to identify and correct any leaks.
Quality homes and doors. A significant portion of the energy we use to heat a home escapes through the windows. Passive houses not only carefully consider the orientation of the openings to maximize solar gain, but also use triple-glazed windows to minimize heat loss.
Reduction of thermal bridges. These are points where the insulating surface is broken (for example, by a nail or the frame of an aluminum window) and allow heat to escape from a building.
Heat recovery ventilation system. Opening windows to ventilate loses heat in winter and lets in cool air in summer. Passive houses have a mechanical ventilation system that filters the air and recovers the house's own heat to warm the incoming air. With this system, it's not necessary to open the windows.
Public regulation
This standard is becoming increasingly common in regions of the world such as the European Union, where institutions require that new constructions get as close as possible to near-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 New York City Mayor Bill de Blasio tried to impose, proposing a ban on the construction of "classic glass and steel skyscrapers, which are incredibly inefficient.".
The measure didn't go through, but it did make many people reflect on the relationship between architecture and climate change. For Kaufmann, De Blasio's proposal makes perfect sense: it's not only more environmentally friendly, it's also cheaper.
"30-50% glass surface is more than enough to get the necessary light. In an office building, for example, only the window area above the desks is useful; everything below that is not. It will be too hot in summer and heat will be lost through there in winter," he reflects.
Can I convert my home into a passive house?
Any home can be converted into a "passive house." The most efficient will be those already built to these standards, but "houses can be renovated following the Passivhaus concept," says Kaufmann.
"It is more common in the renovation of entire buildings or single-family homes," explains Cordero, although that does not mean that an apartment cannot be adapted to get as close as possible to the "passive house" standard.
How much does a passive house cost?
Obviously, investing in quality materials increases the cost of construction. "It's true that it's a little more expensive, but not much more," acknowledges Kaufmann, who estimates the building envelope adds 5-6% to the price. Other elements, such as higher-quality windows, also contribute to the final cost.
"In absolute numbers, we estimate about $100 extra per square meter of living space in a new construction, and a bit more for renovations, about $150-$200 per square meter," the expert explains.
Architect Cordero acknowledges that this type of construction increases the price of housing, especially if the goal is to obtain the certification offered by the Passivhaus Institute, a process that can be lengthy. "It's not mandatory, but ultimately it's a mark of quality," he explains.
With or without the certification, the goal is the same: to save energy. "Customers tell us they want a house whose upkeep isn't an energy drain. In the end, it's common sense: if you're going to make a big investment like building a house, it's better to spend a little more on construction but then have it be more manageable month after month.".
And maintenance? Except for the ventilation system, which requires periodic filter changes, the rest of the maintenance is the same as in conventional buildings.
Ultimately, Kaufmann explains, it's about thinking about the future. Passive architecture requires such low energy consumption that it could be powered solely by renewable energy, something currently impossible for conventional buildings. "That's why we need to reduce its energy demand, for when we no longer have gas or other fossil fuel energy sources in the future.".
A future that, perhaps, is not so far away.
