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Endesa - Electricity, Gas, People

Save energy with passive housing

Published on September 16, 2019

We spoke to architect Jesús María Alonso about the benefits of passive housing and the need to combine quality of life with the fight against climate change.

What is passive housing?

Although it may seem like a novel concept, constructing housing based on sustainability criteria and using environmental and material resources for the purpose of saving energy has been occurring for longer than most believe.

Traditional architecture has always employed glazed balconies or verandas as an intermediate space that allows for heat to be maintained during the winter and protects against the sun during the summer.

Over the years, building models changed; spending less and taking advantage of space was prioritised. Basic issues such as energy efficiency, the integration of the home into the environment or its habitability itself were forgotten.

But today, passive housing is back in style. These homes are built according to the Passive House standard, based on almost zero energy consumption, reduced environmental impact and, of course, increased quality of life.

A passive home consumes 15 kWh per square metre per year in heating and air conditioning, a huge difference from the 112 kWh of existing houses.

Is spending money on building a passive home worth it?

One of the biggest questions when we refer to passive housing is whether you will get your money's worth over the years. Cross-checking data on the cost of the average house with the energy source of a climate control system depending the type of house, it is clear that, in the case of electric heating, home-owners are able to save more and recoup the cost at a much higher percentage than in cases of gas heating.

After 25-30 years of living in a new or existing home, the cost of an electric heating and air conditioning system skyrockets, while the cost in a passive home remains stable. In the case of gas heating and air conditioning, the difference is more noticeable after 40-45 years in the house.

We talked to a passive house architect

We spoke with Jesús María Alonso, an architect with many years of experience in designing this type of building, about passive housing and its benefits.

Question: What criteria do passive homes meet to achieve almost zero energy consumption?

- They must meet certain requirements in terms of actual heating demand (less than 15 kWh/m2 ), cooling demand (also less than 15 kWh/m2), and primary energy demand (hot water and electricity).

In addition, the airtightness of the building must be ensured, not exceeding 0.6 air changes per hour. Compliance with these parameters must be formalised through a physical test and audit.

A home is passive if it manages to keep your energy needs below a certain limit

Question: What concrete solutions does it provides?

- The solutions are focused on two main aspects. On the one hand, the relationship of the house with its environment and its establishment on the plot. The micro-climate of each area must be kept in mind when carrying out the project.

On the other hand, the constructive solution of the home and the materials used are also crucial: superinsulation, high-performance carpentry, eliminating thermal bridges, mechanical heat recovery ventilation systems, etc.

Question: How is it different from conventional housing?

- The main difference is energy efficiency. A passive house consumes less energy than a conventional home does to guarantee thermal comfort inside, which helps, on the one hand, save on the consumption of energy sources and, on the other hand, reduce CO2 emissions. This can combat pollution and climate change.

Another important difference is the reduction of maintenance work, since in passive housing, the fluctuation of temperature and humidity changes inside the house is minor. Materials and equipment suffer less and last longer, preventing construction pathologies related to these changes from emerging.

Question: Is the construction a major investment?

- The cost of carrying out this type of construction is higher than that of "conventional" housing, but taking into account the useful life of a home, the return on the extra investment occurs quickly, between 5 and 10 years.

Passive housing costs more than conventional housing, but in 5 or 10 years there is a return on investment

Question: Do the materials used change according to the area where the home is built?

- In general, each place has its own traditional construction systems, which were adapted over time to the characteristics of the existing materials in the area.

Today, construction systems and their industry have become globalised, which makes resorting to them much more expendable.

The challenge is to complement the traditional materials of each area with new, higher performing materials for the building envelope of the home.

One of the challenges of passive housing is to complement the traditional materials of each area with new, higher performing ones

Question: When you are tasked with a passive housing project, is the first thing you do a study of the climatic conditions of the plot? What other preliminary analyses are performed?

- It is essential to be aware of the micro-climate of the plot and to adapt our solutions to it. But it is equally important to analyse and find the balance between the orientation of the house with respect to the sunlight and the views the plot offers, to assess presence of water on the plot, as well as wooded areas or other obstacles that cast shadows, etc.

Question: With regard to traditional houses, how much energy is saved in these homes? Can you reach 100%? Or in other words, is it possible for energy consumption to be zero?

- The savings are remarkable, reaching even 90% on heating and cooling demand. In real cases, zero consumption is very difficult to achieve.

A passive home can save up to 90% on heating and cooling

Question: How do they save energy?

- Basically taking advantage of clean energy (solar, geothermal) to provide heat, and keeping this heat inside the house through its construction system with high thermal mass.

In the case of warm climates, where the cooling system takes precedence, we must adapt the home's construction by using heat sink materials such as water and installing a smart heating/cooling system. Heat recovery systems with a bypass option are also used, minimising loss due to air change.

Question: Is it possible to change the energy rating of a house built a few years ago in such a way that it is adapted to the zero consumption requirements?

- It depends on each particular case and how the building was built at the time. But the cost of the work that needs to be performed in order to adapt the existing home to the zero consumption requirements would be entirely disproportionate to the value of the house.

Remodelling work that has been performed lately does significantly improve the energy efficiency of the home, although zero consumption cannot be achieved.

Question: Who requests this type of home be built? Individuals, construction companies, public administrations…?

- Many sectors of the population are currently requesting it; individuals in particular are increasingly concerned about the matter, especially in new constructions.

The incentive of public administrations through subsidies is providing a powerful boost to this type of activity, especially in cases of refurbishing and remodelling the housing stock.

Public administrations are helping to boost the construction of passive homes, especially for refurbishments and remodellings

Question: The benefits to the environment are undeniable, but what about for the person living inside?

- Obviously there is the benefit of saving on consumption, which translates into reduced energy bills. But there is also the benefit of thermal comfort, which results in quality of life.

Question: Is it really housing of the future or does the demand pull more towards smart homes?

- Both are compatible and complementary, and they must be so. On the one hand, there is the building as an apparatus and its relationship with the climate and, on the other hand, how this apparatus operates.

Home automation systems can adapt its activity to the particular characteristics of the climate situation and to the needs of the inhabitants at any time.

Question: How is Spain's situation compared to the rest of Europe? Is there an interest in this type of housing?

- Until recently, due to Spain's climate situation, home-owners did not see the need to adapt construction to energy efficiency as being critical, while this was the case in the Nordic countries, for example.

This situation is changing, since people are increasingly aware that, by taking advantage of the country's climatic benefits and with small actions when building, the benefit obtained in the long run is significante.

In Spain, every home spends, on average, €746 on electricity and €266 on natural gas