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

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

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. orientation, to make the most of solar radiation, it is important to optimally organize the arrangement of external fixtures. Orienting the main facade to the south, for example, allows for greater absorption of solar radiation and provides more free heating during the winter months. Whether they are the windows of a multi-story building or the shop windows of a store, properly positioning the openings and providing appropriate shading systems, such as curtains or sunshades, contribute to reducing potential summer overheating;
2. shape ratio, defined as the ratio between the dispersing surface of the building (external walls, roofs, ground floors) 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 shape ratio correspond to a compact building with, proportionally, smaller dispersing surfaces towards the outside, while high values correspond to buildings that present more complex shapes and, therefore, more dispersing with greater penetration and communication with the external environment;
3. use of thermal insulation, made with a layer of insulating material placed on the external walls of the building, ensures lower dispersions to the outside and a pleasant temperature inside the environment in all seasons. Thermal insulation is an excellent tool for both residential and commercial buildings: it reduces heat losses and the energy demand for maintaining the desired temperature;
4. use of thermal windows, which, made with triple glazing, limit heat loss to the maximum. It is also preferred to create large windows to make the most of solar heat;
5. absence of thermal bridges, when creating the layer of thermal insulation, it is important to avoid creating points of discontinuity by laying it continuously. Such points are created when there is a change in resistance to heat transfer and are the cause of moisture and mold formation;
6. use of ventilation systems, VMC machines are capable of providing a constant supply of clean air, free of dust and smog, eliminating humidity and saturated air. Especially in commercial buildings, ventilation systems are very important for extracting stale air and introducing fresh, filtered air, maintaining a healthy environment;
7. attention to air tightness, to ensure maximum thermal comfort, it is indeed advisable to avoid the formation of air leaks, which consequently generate interstitial condensation, causing damage to the building’s structures. In residential buildings, air tightness helps prevent leaks that can undermine the efficiency of the apartment, while in commercial buildings, it helps prevent temperature fluctuations that could harm workers or customers.

7 principles of passive house design

How to integrate the principles of the passive house into renovation workflows

In order to apply the principles of the passive house to building renovation interventions, it is essential to start with the modeling of the existing building using energy certification software.

Indeed, to understand which interventions are worth developing on a building to make it highly energy efficient, it is advisable to model the house taking into account all the factors that influence its thermal behavior.

You will need to model:

• opaque envelope: external walls, internal walls, floors, roofs;
• transparent envelope: windows, bow-windows, skylights;
• thermal center: boiler, air conditioner, heat pumps, water heater;
• thermal bridges.

Once the actual state of the building is defined, you will only need to develop the guided design of the building-system, with the guided definition of energy improvement interventions such as thermal insulation, window replacement, thermal center replacement, etc.

If necessary, to improve parameters such as orientation, you can plan the relocation of transparent elements or the insertion of shading systems.

Subsequently, legal checks according to the nZEB standard can be automatically performed, and the energy behavior of the building can be graphically visualized: this way, you can easily understand if the interventions you are implementing are suitable to transform the building into a passive house!

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

The principles of the passive house and their impact on long-term management and maintenance costs

Creating passive buildings allows for minimizing management and maintenance costs in the long term as it means creating a system capable of controlling energy use, the state of structures, and systems.

By creating a digital twin of the passive house and pairing it with data-based monitoring systems, real-time tracking of every device is possible. Imagine being able to track the energy consumption of the building; this will allow you to immediately correct anomalies or identify waste and inefficiencies.

Intervening promptly means optimizing management and maintenance costs, maximizing the energy efficiency of the dwelling.

Monitoring systems also provide constant feedback on the performance of the structure in real-time: habits, needs, necessities—everything is measured and is useful for making informed decisions.

Balance between form and function: design strategies aligned with Passivhaus standards

The balance between form and function is a very relevant aspect for Passivhaus standards.

If the form of a building is defined by all the elements of the building envelope that separate enclosed spaces from the external environment, the function represents the ultimate purpose for which it is built.

In relation to form, in the thermal design of a building, it is important to keep in mind that:

• as the exposed surface increases, energy losses to the outside in winter and unwanted thermal gains in summer increase;
• as the volume increases, mass and accumulable energy increase, which help to dampen thermal fluctuations.

It is therefore important that, in relation to the aforementioned shape ratio, compact and regular shapes are preferred, with structures that possess significant thermal mass.

As for the function of a building, it is certainly to ensure maximum living comfort for its users: energy efficiency, thermal insulation, air tightness, and adequate ventilation are the key elements.

Beyond insulation: the importance of air tightness

Thermal insulation is fundamental because it reduces losses and ensures comfort in every season. However, in the design of a passive house, there is much more to consider.

Alongside thermal insulation, a fairly relevant aspect is air tightness.

Preventing thermal bridges at joints, edges, and nodes is one of the most efficient energy-saving measures.

For example, imagine a balcony slab directly connected to a concrete floor; it inevitably produces additional thermal losses because it interrupts the external thermal insulation, thus transferring heat outside.

A good technique to solve the problem could be to position the balcony a certain distance from the facade, providing supports separate from the structure to create a continuous insulation layer and simultaneously a continuous air tightness layer.

An air-tight construction can also be effectively achieved, for example, by completely plastering the building on the inside or using membranes, reinforced paper, or wooden panels.

The regional climate and how it influences the design priorities of the passive house

The location of a building influences its environmental comfort conditions due to the climate, and thus the design line of a passive house will change.

In temperate climates, the needs for cooling and reducing solar thermal load only concern the summer period.

The design criterion in this case must be subordinated to the need not to compromise the possibility of utilizing solar radiation during the cold period, which is much longer.

Glazed surfaces, which represent an important element for solar gains, and opaque surfaces, which, by absorbing solar radiation, determine an increase in surface temperature, must be well positioned.

Openings should mainly be placed to the South, as they capture the greatest amount of radiation in winter (when the sun is low on the horizon), while in summer, radiation can be easily screened with careful study of overhangs and the use of shading devices.

In mediterranean climates, it is important to use low-temperature surfaces to reduce heat accumulation in the surroundings.

Transparent surfaces require careful balancing between thermal transmittance, solar factor, and natural light input; moreover, positioning the main facades towards South and North, with a greater axis East-West, allows for more effective control of solar radiation and natural ventilation.

Digital tools that simplify compliance with the principles of the passive house

As can be well understood, the passive house is synonymous with quality because it is built according to precise rules and standards. To achieve such quality standards, an acceleration in the implementation of new technologies in construction processes is also necessary.

The design of passive houses using 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.

The digital twin offers a wide range of practical applications in the field of passive house design, such as:

• the ability to simulate and optimize the behavior of the building in different scenarios;
• advanced management of heating, ventilation, and air conditioning (HVAC) systems;
• the creation of interactive simulation models;
• the development of historical and real-time data analysis on energy use.

Thermal design software is also an excellent tool for dynamically simulating building energy, capable of ensuring the development of designs aimed at achieving Passivhaus principles, environmental comfort, energy efficiency, and environmental sustainability.

Common errors in the implementation of passive house principles on-site

Among the most common errors in the implementation of passive house principles are certainly:

• the use of unsuitable materials: inadequate materials for thermal insulation and low-quality fixtures greatly influence the efficiency of a building;
• poor execution of interventions: the quality of the workforce and proper installation of all materials and building products used have a significant impact;
• the development of a superficial design: the development of a non-detailed design that takes into account the actual conditions of the building and does not simulate its behavior as the shape, dimensions, positioning of opaque and transparent elements, insertion of insulation, air tightness, and systems vary negatively influences the realization of a passive house.

FAQ – Passive House

What is a passive house?

It is a building designed to ensure thermal comfort without the need for traditional heating or cooling systems. It utilizes insulation, high-performance fixtures, controlled ventilation, and renewable energies.

Where does the concept of passive house come from?

The idea was developed in Germany in the late 1980s, with the Passivhaus protocol, thanks to researchers Wolfgang Feist and Bo Adamson.

What are the main advantages of living in a passive house?

Greater durability of the structure, reduced consumption, lower environmental impact, constant thermal comfort, and higher air quality.

What are the fundamental principles for designing a passive house?

Correct orientation, compact shape, continuous insulation, high-performance fixtures, absence of thermal bridges, controlled mechanical ventilation, and attention to air tightness.

Can the passive house model be applied to renovations as well?

Yes. Starting from an energy modeling of the existing building, targeted interventions such as insulation, window replacement, or optimization of systems can be planned.

Does climate influence the design of a passive house?

Yes. In temperate or Mediterranean areas, priorities change: for example, the management of solar radiation, the orientation of facades, and shading strategies.

What digital technologies assist in the design of a passive house?

Tools such as digital twins and energy simulation software allow for predicting performance, optimizing consumption, and monitoring the building in real-time.

What are the most common errors in the realization of a passive house?

Use of inadequate materials, incorrect installation, superficial designs, and lack of accurate energy simulations.