What is a Passivhaus home? Who much does it cost? Frequently asked questions about passive houses

The pandemic and mobility restrictions have revealed the great deficiencies in the Spanish housing stock, especially with regard to energy demand, poor indoor air quality or insulation problems. This has caused that the most demanding sustainable construction, as is the case with, has acquired more importance than ever. Especially, taking into account that, after several years in the process of adapting to the European Directive 2010/31/EU, Spain already has legislation that finally addresses the construction of Nearly Zero Energy Buildings (NEEBs).

Although the current regulations are more lax than the requirements of the Passivhaus certificate, everything indicates that its presence will gain prominence in the coming years due to its numerous advantages: mechanical ventilation as an instrument to keep interior spaces clean and free of contaminants; huge reduction in energy demand, a very important aspect now that we spend much more time at home due to teleworking; constant and comfortable temperature throughout the year… In fact, since the first passive house was approved in Spain in 2010, the number of projects with this seal in our country has now risen to 169, according to data from the Building Platform Passivhaus, half of them having been certified in the last two years.

Achieving this standard is not an easy task, since it is not only necessary to put into practice the demanding requirements that characterize it, but also to obtain the approval of the Passivhaus Institut of Germany, in charge of accrediting whether a building meets the technical levels necessary to be considered as such. But what do you have to do to get that certificate? Is it necessary to hire specialized professionals? What requirements must be met? Is it much more expensive than other types of buildings?

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On the occasion of World Energy Efficiency Day, which is celebrated on March 5, the experts at Sto, a German company based in Spain specializing in the development of materials and construction solutions for sustainable buildings, answer the most frequent questions about the Passivhaus certificate:

What exactly is a passive house?

is a construction standard created in 1988 by the German physicist Wolfgang Feist and the Swedish Bo Adamson, a professor at Lund University. This model responds to a certain type of construction design that seeks to minimize the energy needed for air conditioning, managing to maintain a constant and comfortable environment and temperature throughout the year by optimizing existing resources. The five principles that accompany it are: excellent thermal insulation, high-performance carpentry (triple glazing, low transmittance and correct installation), absence of thermal bridges, air tightness and mechanical ventilation with heat recovery. Any new construction, regardless of its size and use, can be built to Passivhaus standards.

How to obtain the passive house energy certificate?

In 1996 the Passivhaus Institut was born in Darmstadt (Germany), the entity that manages the certificates for passive houses. For this body to grant this recognition, it is necessary to meet these four requirements:

1. Primary energy demand (heating, hot water and electricity):

2. Energy demand in heating and cooling:

3. Air tightness: n50

4. Thermal transmittance of the envelope: U = 0.8 W/m²K in walls with windows, and U = 0.15 W/m²K in opaque walls.

To obtain it, an approved Passivhaus technician must verify during the project and construction phase that the established requirements are met. This specialist will be in charge of sending the relevant documentation to the Passivhaus Institut or to a certifying entity endorsed by this institution (Passivhaus Certifier).

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How much does a passive house cost?

The construction of a passive house has an estimated extra cost of 5% compared to a conventional house. The differences can even reach up to 15% in those Passivhaus of the prime real estate segment. And it is that the price increase is determined, in most cases, by the chosen finishes, design, location of the future home or level of technical knowledge of the chosen architect and builder.

How much long-term savings does betting on this standard mean?

Despite this additional cost, it is worth taking into account the great return on investment of building a passive house. In this case, three factors stand out:

1. Revaluation of the property. A building certified with the Passivhaus standard has an estimated revaluation of 20%.

2. Medium-term amortization due to energy savings. For example: a 120 m² home spends an average of €1,500 per year on heating, and a passive house with the same characteristics can spend €150: up to 90% less.

3. Operating expenses. When energy costs are reduced to close to zero, the property owner is protected from price fluctuations in the energy market.

Is there a Passivhaus certificate for rehabilitation?

Yes, its equivalent is the EnerPHit certification, also issued by the Passivhaus Institut. The objective of this type of rehabilitation is to achieve the greatest possible reduction in energy demand. With a more flexible nature than the Passivhaus certificate by taking into account the difficulties involved in the rehabilitation process of an existing building, it maintains many of its principles and applies specific solutions that adapt to the particularities of the constructions to be rehabilitated.

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