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Passive house

Passive house: what it is, how it works, and 7 basic principles

The passive house is a sustainable, zero-impact, and highly energy-efficient building. Discover what it is, how it works, and its benefits

All interventions in new construction or on existing buildings are driven by a constant search for energy savings and environmental sustainability: optimizing the energy consumption of a building reduces its impact on the surrounding environment and ensures a healthier environment for future generations.

Among the design actions driven by environmental sensitivity, we find the passive house, a very common type of construction in Europe and also spreading in Italy.

Have you ever heard of it? Do you know what it consists of? Discover in this article what it is and how it works.

What is a passive house?

A passive house, also known as a “Passive House” or “Passivhaus,” is a technologically advanced, low-energy-consuming, and highly efficient building.

It has the ability to ensure adequate thermal comfort without resorting to traditional heating or cooling systems and with low or even zero external energy inputs.

With an envelope consisting of insulating materials, it does not require boilers or heat pumps but exploits passive heating, which is obtained from solar radiation transmitted through windows, appliances used inside the dwelling, or the people who live there.

Passive house with high energy efficiency

Passive house with high energy efficiency

How does a passive house work?

A passive house works thanks to the combination of several elements:

  • Thermal insulation, which ensures the maintenance of a constant and homogeneous temperature inside the dwelling, with consequent improvement of living comfort and space healthiness, reducing the risk of moisture and mold formation;
  • Use of thermal windows, which have a dual important role: on one hand, they contribute to increasing the insulation of the passive building, reducing heat loss, on the other hand, they are essential for absorbing heat and transmitting it indoors, thus increasing the sensation of warmth in the cold season;
  • Body heat from the people living in the house or that developed by household appliances.

In addition to these, controlled ventilation and the use of renewable energies are added.

Controlled ventilation extracts the exhausted air from inside the building and introduces fresh oxygen-rich air from the outside. In this way, continuous air exchange is ensured, without loss of heat or coolness, with total well-being of the inhabitants thanks to the achievement of optimal air quality.

Renewable energy systems instead use energy from the sun, earth, wind, or water. In a passive house, solar energy can be captured through solar thermal panels and photovoltaic panels and converted into thermal energy or geothermal energy can be recovered through heat pumps or green walls or roofs can be built for thermal insulation.

History of Passive House

The idea of a passive house was born in the late 1980s, specifically in 1988 in Germany, with the Passive House Protocol, thanks to the collaboration between two university professors, German physicist Wolfgang Feist and Swedish researcher Bo Adamson.

What united them was a passion for sustainable architecture, and this passion led them to work on an ambitious project: to create the so-called “Passive House,” an innovative building technologically advanced and low energy consumption for which the use of heating systems was not necessary.

Their project did not remain incomplete; in fact, from their idea in 1991, a complex of 4 terraced houses was built in Darmstadt with high energy savings compared to the buildings of the time.

Subsequently, in 1996, the Passivhaus Institut was founded in Darmstadt, where studies and dissemination of passive house construction standards continued.

From that moment on, this new wave of sustainability grew more and more, and the phenomenon of the passive house spread like wildfire from Northern Europe to the rest of the continent.

Advantages of a passive house

Living in a passive house has significant advantages, let’s see the main ones:

  1. Quality structure: the passive house built according to strict design rules proves to be much more solid and durable than traditional houses, maintaining optimal performance for a long time and reducing the need for maintenance interventions;
  2. Design and construction according to standards: having to guarantee a certain level of quality, both the design and execution phases are controlled in detail, taking care in the choice of the right materials and optimal installation;
  3. Decrease in environmental impact: the energy efficiency of a passive house reduces its environmental impact, which is very high instead for all other non-efficient homes;
  4. High thermal comfort: the temperature inside the house is always pleasant, warm in winter and cool in summer thanks to the thermal insulation of the external walls and the insertion of thermal windows. Insulation also eliminates the formation of thermal bridges, consequently eliminating the presence of moisture and mold;
  5. Filtered and clean air: the introduction of mechanical ventilation allows filtering incoming air from external pollution and absorbing, simultaneously, the saturated internal air.

The construction cost of a Passive House will be higher than that of a traditional house and generally varies depending on the material in which it will be built. However, this model proves to be advantageous in the long term: being a NZEB building, i.e., zero-impact and highly energy-efficient, it allows to reduce energy consumption by up to 90% compared to a traditional building and guarantees a return on investment within a few years thanks to savings on bills.

As you can well understand, the passive house is therefore synonymous with quality because it is built according to precise rules and standards. To achieve these quality standards, an acceleration in the implementation of new technologies in construction processes is also necessary. The design of passive houses through digital twin can be an important resource for all professionals. The digital twin offers a complete and detailed view of building performance, so the future of designing efficient and highly comfortable passive houses undoubtedly lies in the use of this technology.

7 Principles for designing and building a passive house

To design and build a passive house, it is important to follow 7 basic principles:

  1. Orienting the building to maximize solar radiation absorption is important to organize the layout of external fixtures best. For example, orienting the main façade to the south allows for more solar radiation absorption and achieves greater and free heating in winter periods;
  2. The form factor ratio, defined as the ratio between the dissipating surface of the building (external walls, roofs, floors against the ground) and the heated volume, measures the compactness of a building. This ratio influences the energy performance of the building; in fact, low values of the form factor ratio correspond to a compact building with proportionally lower dissipating surfaces towards the outside, while high values correspond to buildings that have more articulated shapes and, therefore, more dissipating with greater penetration and communication with the outside environment;
  3. The use of thermal insulation, made with a layer of insulating material placed on the external walls of the building, guarantees lower heat losses to the outside and a pleasant temperature inside the environment in all seasons;
  4. The use of thermal windows, made with triple glazing, minimizes heat loss. Large windows are also preferred to make the most of solar heat;
  5. The absence of thermal bridges: in the realization of the thermal insulation layer, it is important to avoid creating points of discontinuity, laying it continuously. Such points are created when there is a change in heat transfer resistance and are the cause of moisture and mold formation;
  6. The use of ventilation systems: VMC machines can provide constant clean air, free of dust and smog, eliminating moisture and saturated air;
  7. Attention to air tightness: to guarantee maximum thermal comfort, it is advisable to avoid the formation of air infiltrations, which generate interstitial condensation, causing damage to the building structures.
7 principles of passive house design

7 principles of passive house design

To meticulously follow these 7 principles, I recommend designing the passive house with the help of software for energy analysis and simulation: modeling the house considering all these factors, which influence its thermal behavior, will be easier if you rely on software that can develop a guided design of the building-system.

Thermal bridges, shading, form factor ratio, ventilation systems, or insulation, everything is managed and verified automatically, allowing you to find the optimal solution to build a zero-impact passive house! What are you waiting for? Try it for free for a month.