What is a Passive House?

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When we talk about a passive house we refer to homes designed with a series of architectural strategies (materials, construction systems, etc.) that guarantee the best level of interior comfort and the lowest energy demand.

 

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Is it the same as “passivhaus”?

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The term “passivhaus” refers to a German certification that was created in the 1980s, where it is credited that the house meets specific technical requirements (the most symbolic is that which establishes a consumption of less than 15 kWh per square meter per year in heating).

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Therefore, we can say that a house can function passively without being certified; instead, a house certified with the “passivhaus” seal will always be a passive house.

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Apart from this certification, the following certifications also exist depending on the country in which each one has different levels of requirement:

 

Ecómetro (Spanish) | VERDE (Spanish) | BREEAM (English) | DGNB (Germany) | MINERGIE (Swiss) | LEED (USA)

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How to make a house passive?

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Once we are clear that it is a passive house, we have to see how we can get it. The main strategies and in summary form are:

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1. Isolation

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Thermal Isolation is a constructive element that helps us keep heat inside the house. It is important since a large part of the consumption of a house is due to heating and, therefore, if we have good thermal insulation it will keep the interior temperature higher and will consume less.
The execution and quality of the insulation material will improve comfort conditions, especially in winter, which is when there is a greater difference between indoor and outdoor temperatures.

 

2. Thermal bridges

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This concept is linked to poor isolation. Thermal bridges are areas or points in which there is a building element that is in contact with the exterior and interior and therefore, the heat loss is considerable. To avoid thermal bridges, continuity in the isolation is important, especially in the meeting between the façade and the roof or the floor. There are also thermal bridges in the windows, but it will be detailed in the next section.

 

3. Quality of openings

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The openings in the house are a solar collection point, but as we have mentioned before, they are also an element through which thermal bridges are generated. So the choices of the carpentry are essential to avoid losing the comfortable heat of the interior.

The glass can be double or triple, with an air chamber and gases inside that improve thermal performance. There are a host of solutions for crystals that help limit energy transmission. As for the carpentry, we have to ensure that there is sealing to avoid the thermal bridge, so if we close all the windows we keep the heat, but when we open them, we get natural ventilation at home to renew the air and improve sanitation.

 

4. Renewable energy

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Including a renewable energy source as an energy contribution helps reduce economic consumption, always guaranteeing comfort. Some of the examples are solar energy, using solar places to generate electricity and / or transform it into hot water. It can also be used through geothermal energy, where the heat accumulated by the land due to heating is used to generate energy in our favour.

 

5. Ventilation

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Ventilation and renewal of indoor air is the last of the factors that guarantee good sanitation. Two strategies to consider are cross ventilation and mechanical ventilation. The latter, by means of a heat recuperator, manages to recover a large part of the energy that comes out through the ventilation.

 

For these passive measures to give results, it is necessary that the design of each house adapt to the climate in which it is going to be built, making it impossible to transfer the project to other countries with different climates.

 

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What is the savings in energy consumption?

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Without going into details, to take an example of a conventional house, the energy demand is between 110 and 150 kWh per square meter per year. If we compare it with the 15 kWh / m² that a “passivhaus” needs, we can see that the result is almost 10 times greater.

 

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Finally, how much does it cost to build a passive house?

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If we speak in terms of costs, it is true that a bioclimatic house may have a higher cost (between 5 and 20% more), but we have to appreciate that this initial increase is going to become a short-term savings. Taking into account that the useful life of a home is 50 years, with the energy efficiency of a passive house you will be able to reduce costs in a few years.