Allora sei nel posto giusto per un restyling di qualità! Invia una piantina via mail con la tua wish list ed i tuoi recapiti, ti ricontatteremo con una soluzione interessante!


Then you are in the right place for a quality restyling! Send a plan via e-mail with your wish list and your contact details, we'll get back to you with an interesting solution!
Passivhaus 2017-10-10T10:39:20+00:00

We are PASSIVHAUS certified manufacturers

We are able to provide the design, the calculation for energy savings and energy requirements energetico of the buildings, the calculation for the improvement of energy efficiency energetic and the building up to gain the Passivhaus certification.

Technical details

What is a Passivhaus?

House comfort and energy savings.
“Passivhaus” is a building criterion that either in the design and execution phase, provides that a building is able to ensure thermal comfort whitout or whit a minimum of external energy source, taking advantage of the sum of the heat generated internally to the building, of passive inputs’ solar irradiation through the windows, of heat dissipation of household appliances, and of heat generated by the occupants. Hence the use of the term “Passiv”.

“The heat loss of the building are reduced to such an extent, that almost makes you not even need an active heating system. The passive heat inputs such as the sun, tenants, appliances and heat recovered from the exhaust air, cover much of the heat requirement. The remaining heat can be supplied by means of air exchange, if the maximum thermal load for heating is less than 10W for square meter of useful surface. If the only heat input in the building comes from input air, the building can be defined Passivhaus”

Prof. Dr. Wolfgang Feist
Chair of Construction Low Consumption and Building Physics at the University of Innsbruck (A) and Director of the Passivhaus Institut in Darmstadt (D)

efficienza energetica

il termos mantiene il caldo con l’isolamento, la macchina del caffè tramite energia

Passive houses are buildings compliant to European Directive 2010/31/UE, adopted by the Italian government with Law Decree n. 63/2013 and subsequent L.90/2013, fixing the OBLIGATION  for new construction and renovations, to achieve the passive house standard from 31/12/2020.


Specifically, following criteria established by the American standard ASHRAE 55-2004, to certify a house according to the criteria “Passivhaus”, the following parameters must be obligatorily met:
  • Heat requirements  ≤ 15 kWh/(m2a) or: specific thermal load ≤ 10 W/m2
  • Cooling requirement ≤ 15 kWh/(m2a)
  • Air Tightness n50 ≤ 0,6 h-1
  • Primary energy demand ≤ 120 kWh/(m2a)
  • Low overheating in summer (n. gg. < 10% con Ti > 25 °C)

While it is recommended but not required to meet these other parameters:

  • No thermal bridge design
  • Thermal break windows Uw ≤ 0,8 W/m2K
  • Highly efficient systems; internal ventilation with more than 75% of heat recovery
  • Low heat losses for preparation and ACS distribution
  • Efficient use of electricity.


A passive house is a building that must meet certain criteria: among others, heat requirement (energy necessary for heating the environment) and the cooling requirements (energy necessary for cooling the environment) must remain below 15 kWh/m2 year, primary energy requirement must be less than 120 kWh/m2 year (primary energy consumption for heating, cooling, domestic hot water preparation and distribution, electricity for household appliances and “auxiliary ” electric current, which is for servicing equipment) and n50 value (replacement of inside air by leakage through the drafts with a depression/overpressure of n50 value (replacement of inside air by leakage through the drafts with a depression/overpressure of 50 Pascal) should result less than 0.6 h-1.
Thanks to the achievement of these values it is generally possible to ensure thermal comfort without the need for installation of any of the conventional “heating system”, or of a boiler, radiators or similar.
The energy necessary to balance the residual heat needs of the structure is usually provided by non-conventional systems (eg. Solar panels or “heat pump” to heat the air-controlled mechanical system with high heat recovery ventilation).
These performances are obtained adopting a very careful design, especially related to the sun, using high performance thermal insulation on external walls, roof , and glass surfaces and controlled ventilation systems for energy recovery.

efficienza energetica

Caratteristiche tecniche

The 5 fundamentals of the Passivhaus standard

  • Excellent thermal protection of all structural components of the thermal envelope from the floor to the external walls to the roof;
  • Windows and French Doors with double/triple low emissivity glazed units with a high value of “g” solar factor and very well insulated frames; careful design and control of passive solar gains, thoroughly planning window areas, possibly differentiated for each side of the building, and ensuring the absence of overheating in summer;
  • Execution according to the best practices of the heat protection taking into account up to the smallest details with the minimization of all thermal bridges;
  • Air-tightness of the exterior building elements checked using pressure testing Blower Door;
  • Controlled ventilation with high efficiency heat recovery to prevent heat loss while ensuring an adequate quality of indoor air.

The 5 fundamentals of the Passivhaus standard


→Low consumption
– Consumption is about 90% less than a conventional home, and about 75% less than new homes energy efficient gained by eliminating traditional heating systems.
– Ensures itself a perfect indoor air quality, with ease and with simple and reliable technical devices.

→High levels of comfort
– Ensures thermal wellness without or with a minimal energy source of internal heating or without using “conventional” heating system, ie boiler and radiators or similar systems.
– Unparalleled and consistent interior comfort levels.
– Temperatures and heat equally distributed in all the rooms.
– No significant change in temperature or annoying drafts.

→Removal of mold, moisture, air currents
– Thanks to the controlled mechanical ventilation (or CMV) air circulation inside the house is always optimal thus preventing the formation of harmful mold or air currents that might annoy those who present problems to the respiratory system.

→Increased sound insulation
– A benefit derived from the passive construction techniques is the superior level of sound insulation.

→Earthquake-proof building
-The passive house has special earthquake-resistant qualities which makes of it an ideal building for areas subject to earthquakes and natural disasters.

What’s special about our Passivhaus?

» It uses between 85% and 95% less energy than a traditional building;
» It is surrounded by a perfectly sealed building envelope (do not let air out and does not let it in);
» It can be bio a& eco sustainable;
» The material of which it is made, may be recyclable up to 60%;
» A constant balance of internal moisture in the house is kept to reach an optimum level of health, avoiding the formation of condensation, mold and bacteria;
» Excellent sound isolation;
» It is Antiseismic;
» It is independent of fossil fuels;
» Reduced maintenance costs of the plants;
» Emissions of harmful volatile substances in the environments close to zero
» It makes no dust;
» It controls and minimizes internal and external electromagnetic fields;
» Revaluation of property in time thanks to the high quality of construction standards;
» Building Certified with appropriate quality controls.


Building from scratch, or the renovation of a building according to passivhaus standard entails, sometimes, , a significant expense, higher compared to conventional buildings. This higher cost is absorbed by the savings on the spending bills over a maximum 5 years, on the average.
To give an order of magnitude adopting this standard, you spend only around 1 €/sqm per year for heating.

The most interesting aspect is the revaluation of the good, let’s consider for example the recent events, i.e. the obligation from January 1, 2009, for all houses for sale and now also for rent, to declare their energy efficiency class. Since then, potential buyers have started to correlate the cost of the property purchase with energy efficiency features (ie less spending on bills) favoring the purchase or lease of a building closer to class A.
What is nowadays the value of Class A property with respect to a class-G? And what would be the value of a Class G sold in 10 years?
Would you ever buy a property that in four years will be comparable to the energy class D and that no one will want to pay the price at which you bought it?
If you browse a bit the property listings you already know the answer.

“Certified homes have more amenities, are subject to lower depreciation, are tradable on the market”.

Given these considerations and the fact that the passive house is a house compliant to “norm” as from 2021, it’s worth thinking starting from now in a forward-looking, to make a good investment.

What is meant by living comfort?

A building is healthy and comfortable when it returns us a feeling of well-being. The Passive House has as its goal the welfare and human health. Assuming that we spend approximately 80% of our time in a closed environment, it is good that this environment is healthy and comfortable. For more technical detailsclick here.

Healthy air Indoor

Unfortunately, much of the building materials, furniture and objects, contain pollutants, and this is combined with construction techniques that allow the circulation of dust and pollen, to the point that a real disease called Syndrome of ‘ sick building , has been introduced, which is diagnosed as the building is so harmful as to compromise the health of those who live or work there.
Traditional buildings do not take into account this factor that instead is fundamental in Passive House. More: in traditional houses “indoor” pollutants concentration were recorded (by means of appropriate detection tools) far superior to outdoor pollution !!!
Indoor air quality is affected by many polluting factors (internal and external) determined by the introduction of new substances into the atmosphere and the increase of all combustion processes.
The vast majority chemical indoor pollution comes from large category of Volatile Organic Compounds (VOC): a great variety of molecules that differentiate to the degree of harmfulness and organoleptic impact, easily evaporable from the building envelope or from the surfaces of the furniture in it, that spreads in the in air at ambient temperature.
So far more than 900 different VOCs have been identified and in domestic and confined environments can be detected from 50 to about 300 of them; environmental impact of the gaseous pollutants can manifest itself in different forms and not only in volatile form.
PAHs (polycyclic aromatic hydrocarbons) are highly lipophilic and have the ability to adhere to the organic material, which is why they can easily accumulate in the lipid tissues of living organisms.
The Ministry of Health recorded a strong increase of multisystemic diseases with often unknown origin to which is assigned the name of “rare diseases”; many of these are defined psychosomatic or hereditary lack of etiologic elements compatible with traditional medicine. In 2006 they esteemed between 6000 and 7000.

Homogeneous temperature

First, the climate within which a person lives, directly affects the comfort: the feelings of “hot” or “cold” are evidently connected to outdoor weather conditions. Moreover scientific studies on comfort have shown that optimal environmental conditions do not remain constant throughout the year, but fluctuate with the seasons. A person can define the same conditions as “too hot”, “too cold” or “comfortable” according to the time of year. It has been demonstrated that these changes in expectation are connected to the climatic conditions that the person has lived in, during the 3-4 weeks prior to the test. This phenomenon is called “personal history of comfort“.
A second set of factors that influence the comfort is tied to the individual: after all, we are all different from each other. Scientific research has shown that the optimal comfort conditions are also influenced demographic factors. In Italy, a classic stereotype regards the Germans, known to show up in Riviera to bathe already in May, when no Italian would dare to get close to the water. Beyond the obvious generalizations typical of all stereotypes, this one in particular shows how cultural, demographic factors and personal history on comfort, influence of our choices.
A further group of factors that influence the conditions of comfort, and that does not require changing clothing, is the kind of
physical activity of people.
What we have described so far exclusively relates to individuals, and their relationship to the climate in which they live.
To completely address the issue of comfort inside buildings, we need to add to the list another couple of group. Physical factors, that within a building, directly influence the perception of comfort, include the radiant temperature of the interior surfaces (walls, floor, ceiling, doors, etc..), as well as the temperature, relative humidity, and indoor air speed. For this reason, the hygrothermal comfort in a building depends directly on the quality of its thermal envelope, on the absence of thermal bridges, and on the absence of drafts (air tightness). These aspects of the building not only affect its energy efficiency, but also the welfare of its inhabitants. The energy class of a building, in fact, is not sufficient to determine its true quality in terms of comfort.
The thermal comfort is only guaranteed if the temperatures within an environment (air temperature, but also of the floors, walls, windows etc.) are homogeneous, with very limited local temperature differences.
An environment with uniform temperature (top picture) is comfortable: the radiant temperature of the windows (18 ° C) does not differ much from that of the walls (20.5 ° C). An environment with very different radiant temperatures (bottom picture), it is not comfortable: even if the wall temperature is above 20 ° C, if coldest areas are present (not performing windows, thermal bridges, etc.), the perception will be that of a cold environment.
High energy performance windows can greatly improve the thermal comfort, as they maintain an average internal surface temperature greater than 17° C. Even in full winter time, there is no experience of a significant decrease in the surface temperature of the windows.
The hygrometric comfort is instead given by a proper level of humidity: neither too dry nor too wet.
Too often, those who deal with energy do not care about comfort: countless redevelopment for energy consumption improvement (replacement of windows and doors, construction of thermal coats) are performed only thinking about energy, and not about people. This often leads to disastrous results, with the house that is filled with mold and condensation.
The last group of factors includes the psychological aspects of how a person perceives comfort, and how he/she can control the environment. Are you able to control fully or partially thermo-hygrometric conditions? Can you open the windows? If it is a work environment, such as an office, is it possible to remove a piece of clothing? Often the mere confidence of being able to act on living conditions is in itself enough to make us feel at ease.
We take this opportunity to debunk the cliché – absolutely ridiculous and false – that in a Passive House windows cannot be opened.
Unfortunately many ignorant and out of date designers, for fear of losing customers against the growing movement of passive houses, use this cliché to defend old design methods, and intimidate customers in front of innovative choices, less related to plant.
It goes without saying, that this works to the advantage of the designers, not the buyers.

Humidity monitoring

Thanks to the strong insulation, heat remains inside the house and all surfaces have a uniform and pleasantly warm temperature. In this way, in a passive house there is no radiant temperature asymmetry between outer walls and related air currents do not form.
Conversely, the scorching heat of the summer is out and prevents overheating.
In a passive house there is therefore a pleasant indoor climate, constant throughout the year, which ensures to those who live in, a high level of comfort.
Also passive houses use highly efficient ventilation systems (CMV), which prevent the formation of mold, bacteria and dust with related allergies.
The passive house heats and cools only using a CMV system (Controlled Mechanical Ventilation) which, among other things, provides for a hygienic renewal of air (without indoor air treatment or other traditional systems).

Sound Insulation

Silence makes the environment calm and relaxing.
For several years the noise became one of the first sources of pollution, stress and discomfort, and consequently men have the need to protect themselves from sounds and noises.
A noise is a set of sound vibrations that correspond to changes in air pressure audible by humans. Here are just some examples of sources of noise that we face every dayoutside noise (road, rail and air); noises coming from inside (hi-fi systems, technology, heating, ventilation); impact noise (generated by objects falling on the floors, the noise of shoe heels). Acoustic insulation is the set of measures taken to reduce the transmission of energy from sources that produce it to the places that need to be protected. Therefore, sound insulation purpose is to protect men from the noise, mitigating or eliminating its perception through sound energy dissipation.

Renovations – EnerPHit

Since 2010 there is a special protocol called EnerPHit (Quality-Approved Energy Retrofit with Passive House Components) developed by the Passivhaus Institut for energy upgrading of existing buildings, ensuring a reduction in consumption between 70 and 90%.
The renovated buildings with EnerPHit standards offer an optimal level of thermal comfort, a high degree of user satisfaction and construction elements exceptionally healthy, in particular preventing mold or condensation.
In renovations, there are several obstacles presenting the achievement of Passivhaus standard, such as architectural constraints, functional layers no longer reachable if not with a prohibitive and unjustifiable expense, shading suboptimal situations, difficult elimination of certain thermal bridges etc.
For this reason, it was recognized the need to introduce a new standard that ensures living comfort while respecting the need for reasonable interventions from an economic point of view.
There are two types of EnerPHit certification, the method based on heating/ cooling requirements, that similar to what you do for new buildings provides for limits on consumption for heating and cooling/dehumidification of the building,
And the method for components where limit values are provided for each constructive component that you are going to use in the renovated building (eg. limits on U-values of walls, windows and doors, the ventilation system efficiency, etc.) ..
Both methods provide limit values that vary depending on the climate zone in which the building is constructed. Moreover, even for EnerPHit certification three classes have been identified: Classic, Plus, and Premium.

From 2016, following the developments of EuroPHit project, you can also certify buildings that are renovated with a step-by-step approach, ie buildings that are not fully modernized with a single intervention but whose restructuring process involves several interventions distributed over the years. This approach involves the release of a pre-certificate following the drafting of a “EnerPHit Restructuring Plan” and the implementation of a first step (intervention) of upgrading . Subsequently, as soon as all steps are completed and the whole building will be renovated to the passive house principles, we will release the final EnerPHit certificate.
As we mentioned before, the parameters specified for EnerPhit Protocol are less restrictive than the Passivhaus as can be easily seen from the below diagram.


Enerphit class



Certifications are significant for the customer since they represent a proof of quality assurance and of the achievement of expected energy values and welfare.
For this reason we suggest to immediately certify a house built or restored according to the Passivhaus standard, so that you will have a check of performance as prepared in the planning stage, as well as an official recognition by the Passivhaus Institut in Darmstadt allowing you to revalue your property over time without losing the invested value.
The cost of certification is affordable, in the order of a few thousand euros, and is performed by a third party accredited by Passivhaus Institut.
The correct procedure for starting a certification process is to involve the Certification Authority from the beginning, in the design phase. This allows you to correct any problem during construction, thus avoiding unpleasant surprises and ensuring the full achievement of Passivhaus requirements.
The Passivhaus protocol can be integrated with all other environmental sustainability certifications, without neglecting the respect of national hygrometric, acoustic, and fire resistance minimal requirements.
The granted certification may be of different types depending on the different classes to whom the building belongs, according to Darmstadt Institute classification.
Passivhaus Classes


Where does the Passivhaus standard come from?

The Passivhaus standard was born in May 1988 from a collaboration between Bo Adamson of Lund University in Sweden and Wolfgang Feist of the Institut für Umwelt und Wohnen (Institute for Environment and Construction) in Germany. Their idea was then developed through a number of research projects, with financial support from the German state of Hessen. The first Passivhaus houses were built in Darmstadt, Germany in 1990, and owner-occupied the following year.
The Passivhaus Institut was founded in September 1996, also in Darmstadt to promote and control the standard. Since than thousands of Passivhaus buildings have been built, to just over 25,000 units in 2010, but it is assumed the number to be around 50,000 units. Most of them are located in Germany and Austria, but have been realized in many various other countries around the world. The city of Heidelberg in Germany has recently launched the Bahnstadt project, which consists in the construction of the largest area in the world with buildings built according to the Passivhaus standard.


The era of cheap fossil fuels, which lasted about 100 years, is almost at the end. In this age many mechanical and electrical equipment have been developed to heat, cool, ventilate and illuminate the interior of our buildings.
A new profession, that of the plant engineer, was born to design and locate “active” (mechanical) plants, suitable for the different types of buildings.
One of the consequences of choosing to artificially influence the interior was that the building envelope ceased to be the primary moderator of the external climate towards the internal environment, and so architects gave the responsibility of the environmental control design to engineers. But as a result of the oil crisis in 1973, many architects and engineers considered wise to reduce the dependence on fossil fuels, and developed a renewed interest in the rich, varied and refined word of an architecture adapting the internal environment to the changing of season, according to a clever design. This led to a rediscovery of the principles of environmental control through the manipulation of the building shape, the arrangement of the openings, and the thermal performance of materials: the so-called “passive design”.
The passive design strives to maximize the thermal and environmental benefits that can arise through careful consideration of the thermal performance of building components and systems, so as to minimize heat loss in winter and summer heat gains. A purely “passive design” would exclude any mechanical intervention. But this was often inappropriate, since the use of electrical or mechanical equipment (in particular to exert a control function) is normally desirable to allow the passive elements to operate properly.
The “passive design” is therefore a generic term, and is used to define a strategic approach to design, open to interpretation by several people in different climates and locations, with the goal of minimizing the consumption of fossil fuels for heating , ventilation, lighting and cooling.
In Northern Europe the energy requirements for heating is predominant, while in Southern Europe the residential heating needs are minimal, but the mechanical cooling demand increased significantly along the years. Therefore, a growing interest arose on strategies to achieve both “passive heating” and “passive cooling “.
Design strategies for passive heating and cooling rely on the exploitation of environmental heat sources (eg. the sun) and the so-called wells (eg. the starry sky). Most of the initial work in this area was done in the US in the 70s, under Carter administration.
The work was then collected and further developed in Europe in the 80s, using European Commission funds for research and development programs. It is in this context that the Passivhaus concept was developed.

Let’s dispel some of the myths about Passivhaus (FAQ)

The main obstacle is the cultural resistance of a sector – the construction industry – very traditional.
Accurate planning and and execution careful to details, made skilfully by qualified and certified companies, are fundamental, allows you to ensure the achievement of the highest standards in terms of economy, energy savings and welfare housing.

ZEB is therefore a reliable partner, ideal for the construction of a turnkey passive building with guaranteed and certificate result.
To own a building that does not require almost any maintenance (apart from cleaning of mechanical ventilation filters) is what you would always like to wish. The goodness of the insulation and mechanical ventilation systems preserve the building by repeated maintenance intervention and delay their execution, thus increasing the return on investment.

First “super-isolated” buildings were built, experimentally, between the mid seventies and mid-eighties, following the first oil crisis. See for example the Rocky Mountain Institute, built in 1982-83 in Snowmass in Colorado.
Passive standard was then refined in the early nineties, and has remained largely unchanged over the last twenty five years.
There is nothing experimental in a Passive House.

It depends on how you calculates its cosy.

We are the “Land of the Sun”, with more than eight thousand kilometers of coastline. But if we look at the data, we find that over 40% of our population lives in the climate zone E or F.
When you hear that something “is not needed,” try asking on what basis the analysis has been done.
To ensure the comfort and health in any type of building, it is necessary to exchange indoor air to bring oxygen and remove water vapor and carbon dioxide. In our article on controlled mechanical ventilation, we have addressed this issue in detail.
Define the mechanical ventilation as an iron lung (or similar expressions) indicates ignorance in the topic of air quality inside buildings.
A thermal bridge is a thermal wrap discontinuity, where the heat flux is greater than the rest of the structures.
Thinking that by not isolating thermal bridges can help the “cooling” of the building in summer denotes ignorance. In addition, the presence of thermal bridges is a major cause of the occurrence of mold and condensation: to propose to keep these weaknesses is irresponsible.
Sample analysis of a thermal bridge: a pillar within an outer wall
In designing a Passive House an energy balance between the thermal envelope and the climate of the place is considered.
The more the climate is cold, the more the house will depend on free heating (“passive”) given by the sun through the windows.
In more temperate climates, this need for windows is reduced, on the contrary it becomes counterproductive for the summer balance.
If the Passive House is well designed, the amount of windows is optimized according to the climate in which it is built.
Generally the definition of a building as “too tight” indicates a lack of knowledge in terms of comfort (indoor air quality, absence of mold and / or condensation) and of durability of the building.
You can build this kind of buildings employing absolutely standard materials, available in the market for decades.
This is the “prince” of clichés: it is absolutely not true!
In the case of Passive Houses in Cavriago, for instance, all the windows can be opened.
The high quality construction level of passive standard is not tied to a specific manufacturing technology: Passive Houses exist in masonry, reinforced concrete, wood, steel frame etc … but it comes from the thermal wrap performance.
If well-designed and well-built, it is the casing the very high performance component in a Passive House: for this reason, it is not often necessary to have a traditional heating system (with radiators or underfloor). Any heating system can be extremely simple and easy to handle.
Usually, the thermal casing requires much less maintenance than a plant. Maintenance of the “thermal” component in a Passive House is therefore generally less impacting than in a “normal” building.
The first step for achieving this level of comfort and energy efficiency is a conscious architectural project.
For this reason, preliminary design tools are used that allows the development of the architectural and thermal concept at the same time from the initial stages of the project.
This kind of building does not have a particular architectural style, and the beauty or ugliness of the result, as in all buildings, depends on the skill of the architect.
This is also possible in a Passive House, if the plant is well designed.
Un ponte termico è una zona locale dell’involucro termico in cui sia presente una discontinutà (data dalla geometria delle strutture o dai materiali), tale per cui il flusso di calore tra interno ed esterno è diverso – in genere maggiore – rispetto al resto delle strutture.

Sono quindi ponti termici gli elementi strutturali presenti nell’involucro, specialmente se passano gli strati isolanti. Sono inoltre ponti termici geometrici gli stessi spigoli dell’involucro termico di un edificio.

Dal punto di vista dell’energia,
un ponte termico comporta in genere maggiori dispersioni di calore, e occorre tenerne conto nel calcolo del fabbisogno energetico complessivo dell’edificio. Il calcolo del maggiore flusso di calore va eseguito con software di calcolo agli elementi finiti, validati secondo la UNI EN ISO 10211, anche se la maggior parte dei tecnici non approfondisce il progetto dell’involucro termico fino a questo livello (limitandosi alla vecchia e superata norma UNI EN 14683 o ad abaci di ponti termici precalcolati).

Dal punto di vista del comfort,
invece, questi punti deboli comportano delle temperature più basse rispetto alle superfici interne degli elementi dell’involucro (pareti, tetto ecc.): situazioni di questo tipo causano discomfort (“sento freddo”), e possono portare alla formazione di muffe e condensa. Per questo motivo, specialmente nel caso di ristrutturazioni o riqualificazioni energetiche, è necessario sviluppare questi dettagli costruttivi con software di calcolo agli elementi finiti, validati secondo la UNI EN ISO 13788, per avere la garanzia che tutti i ponti termici vengano risolti ai fini del comfort (“non sento freddo” e “non ho muffa”).

A thermal bridge is a local area in a thermal wrap where there is a discontinuity (due to the geometry of the structures or of materials), such that the flow of heat between inside and outside is different – usually it is higher – than the rest of structures.
So usually the structural elements present in the casing are thermal bridges, especially if they are cross insulating layers. The same edges of the thermal wrap of a building are geometric thermal bridges.
From the energy point of view, a thermal bridge typically involves further heat loss, and should be taken into account in the calculation of the total energy needs of the building. The calculation of the greater heat flow should be performed with finite element software, validated according to the UNI EN ISO 10211, although the majority of technical does not elaborate projects on the thermal wrap up to this level (merely adopting the old and outdated UNI EN 14683 rule or using tables of pre-calculated thermal bridges).
From the point of view of comfort, however, these weak points involve lower temperatures compared to the inner surfaces of wrap elements (walls, roof, etc.). Similar situations cause discomfort (“I feel cold”), and can lead to the formation of mold and condensation. For this reason, especially in the case of renovation or of energy requalifications, it is necessary to analyze these constructional details using finite element computational software, validated according to UNI EN ISO 13788 norm, to have a guarantee that all the thermal bridges are removed for the purposes of comfort (“I do not feel cold,” and “I do not have mold”).
For the design of high-quality and high comfort buildings, such as Passive Houses, it is crucial to plan in order to eliminate thermal bridges caused by the discontinuity of the materials. Regarding the geometric thermal bridges, although it is not conceivable to eliminate all the edges of a building (unless you want a ball-shaped house), it is certainly better to prefer simple shapes for the thermal envelope.
A compact building not only has less geometric thermal bridges, but it is also better in terms of seismic and it is cheaper to build.
In case of a restructuring or upgrading the energy efficiency, it may not be possible to completely eliminate the structural and geometric thermal bridges: then it is necessary to design in such a way as to ensure the comfort, providing an even indoor temperature, and minimizing heat dispersions.

For renovations there is a specific protocol called EnerPHit. (Quality-Approved Energy Retrofit with Passive House Components) developed by the Passivhaus Institut.
Buildings renovated with the EnerPHit standards provide an optimal level of thermal comfort, a high degree of satisfaction of users and an exceptional healthiness of constructional elements, in particular with the absence of mold or condensation.
Even for EnerPHit certification there are three classes: Classic, Plus and Premium.
The parameters that must be met in a EnerPhit restructuring should be as follows:
– thermal demand for heating ≤ 25 kWh / (m2a)
– Percentage of hours per year with internal temperatures above 25 ° C without active cooling ≤ 10%
– primary energy demand ≤ 120 kWh / (m2a)
– tightness n50 ≤ 1.0 h-1
Starting from 2016, according to the developments of EuroPHit project, you can also certify buildings renovated with a step-by-step approach, ie buildings that are not fully modernized with a single intervention but whose restructuring process involves several interventions diluted over the years. This approach involves the release of a pre-certificate following the drafting of a “EnerPHit Restructuring Plan” and the implementation of a first step (intervention) of renovation. Then, as soon as all steps are completed and the entire building will be renovated according to Passivhaus standards, the final EnerPHit certificate will be released.
For more detail please read the above specific item dell’articolo poco sopra.
It exists a certification either for new or renovated buildings according to the Passivhaus standard; the Certifier is a third party accredited at the Passivhaus Institut, prices are affordable and are the certification is, for the customer, an assurance of the quality and of the achievement of the energy and wellness objectives of the project.
There are also certified materials such as window frames, entrance doors, insulators, etc ….
For both Passivhaus and EnerPhit certification, the Darmstadt Institute has provided a breakdown into the three Classic, Plus and Premium classes; this certification can be integrated with all other environmental sustainability certifications.
It is not mandatory but it is recommended, so there is a scientific feedback as well as a revaluation of the property.
For more details refer to the above.
The parameters that significantly affect the energy balance in a building, as shown by the chart below, are the insulation of the casing and the ventilation.
Both are closely related to the air-tightness of the building casing or better, to the degree of tightness of the casing system made up of various constructive elements interconnected in various ways. These connections represent preferred routes for heat transfer, resulting in an increased thermal dispersion through the casing. A typical example are air flows occurring at the point contact of windows to the wall structures. Such air infiltration is directly responsible for the increase in the air permeability of the building, defined by the amount of air crossing the building casing due to the pressure difference between indoor and outdoor environments.
Such low air-tightness of the casing causes:
– increased thermal dispersion in winter by convection resulting in increased heating requirements
– risk of condensation formation inside strata due to the passage of steam from the inside outwards (winter) and from the outside to the interior (summer) resulting in worsening of the insulation properties of the structures
– Reduced comfort of indoor environments due to the presence of small air flows which cause a local decrease in surface temperature (local discomfort) or of entry into the room of cold/hot air flows (winter/summer) with consequent decrease/increase of relative humidity rate.
– acoustic bridges: air entering through air flows is a good vehicle of external noises
– reduction in the efficiency of mechanical ventilation systems with heat recovery. The heat contained in the hot air when dispersed outside through slits can not be recovered.
In order to avoid such phenomena, it is necessary to design building solutions ensuring good air-tightness for the entire housing. Air tightness is ensured adopting an internal air-tight layer preventing the passage of airflows from the inside to the outside. To minimize the thermal dispersion by convection, an outer wind-proof sealing layer is added.
The air-tight layer is usually made on the inner side before the insulating layer and must contain the entire heated volume without any interruption and discontinuity. It also acts as a steam brake.
The air-tightness of a building is measured using the Blower Door Test, which allows to evaluate the permeability of the casing by calculating the air intake by infiltration, creating a pressure difference between inside and outside of 50 Pa (1 Pascal represents the force of 1 N exerted on a surface of 1m2: the generated pressure in the 50 Pascal test corresponds to about a dynamic pressure generated on a wall subjected to perpendicular wind action at a speed of 9 m s.
The test is carried out using a fan which, suitably installed on an external door or window (all other openings are closed), draws air out of the building to create a pressure difference of 50 Pa between inside and outside. Suitable instruments are used to measure the air flows induced by the fan inside the building and the possible air exchange through leaks in the casing.
The Blower Door Test includes a pressurization phase where the fan blows air inside the building in 10 Pa pressure increments and a depressurization stage where pressure decreases. The number of hourly exchanges obtained in these conditions is indicated by the symbol n50 expressed in h-1.
Summarizing, n value is the amount of air exchanged every hour inside the building and can be calculated using the formula: n50 = V50 / V [h-1]. Where V50 = air flow rate measured with ΔP = [M3 / h] and V = air volume in the building [m3 / h].
Existing national regulations do not impose any air permeability requirements for the enclosure in newly constructed buildings or subject to energy-refurbishment.
However, today there are various municipalities and provinces in the country that adopt in their building regulations energy certification protocols that impose air tightness requirements on buildings. They introducing n50 air emission limit values certified using the Blower Door Test .
The Casaclima Certification Protocol of the Bolzano Agency fixes for all new residential buildings a limit n50 value according to the energy class.
A house built according to passivhaus standard is characterized by a high casing tightness with a value of n50 ≤ 0.6 h-1
The test for air-tightness using the Blower Door Test provides for two methodologies as required by UNI EN 13829:
Method B: Used to control the quality of work and to detect leaks in the enclosure under construction. The search for any leakage of air is carried out through appropriate instruments such as thermo-anemometers, thermo-cameras, smoke generators.
Method A: The test is performed when the casing is in the operating conditions suitable for a fully operational heating or cooling systems. All external openings are closed and all internal left open. This method is used to determine the n50 value.

blower-door-test home-energy-audit-4
High thermal performance of the casing in a passive house allows the use of more efficient and cost-effective plant solutions than traditional systems. The demand for energy needed for winter heating is generally covered through a ventilation system and a high efficiency heat recovery (η ≥75%). The ventilation system consists of a double pipe system:
– A duct that draws air from the outside
– A series of ducts that supply the outside air, heated by the recuperator, to main environments such as rooms, living rooms, studios …
– A series of ducts that take exhausted air from environments such as kitchens, bathrooms
– An exhaust air expulsion duct installed after the recuperator where much of the heat is transferred to the inlet air.
The ventilation system of a passive house is often combined with an underground heat exchanger consisting of two polyethylene pipes corrugated on the outer surface (to increase the heat exchange surface) and smooth and white on the inner surface (to facilitate any inspection). The pipes, placed at a depth of about 100-150 cm, are sized according to the size of the building and to the volumetric flow rate of the heat exchanger.
The outside air, taken by inlet generally placed in the garden or away from polluting sources, is passed through high quality filters (F7 or higher) and then arrives at the entrance point of the building at temperatures of about 5-8 ° C.
Where additional heating is required, plants with a limited power of 0.5 to 1.5 kW (heat pumps, …) are used. The refreshing air is supplied in the various environments through inlet vents generally spaced 15-20 cm from the ceiling to allow better air distribution within the environment (coanda effect).
The quality of indoor air (IAQ) is an absolute priority of a passive house where the healthy indoor climate is obtained through: compliance with the thermal comfort criteria, including preventing areas with local heat discomfort; controlled ventilation that ensures good indoor air quality.
Without controlled ventilation, CO2 concentration above certain limits will adversely affect the living comfort
To maintain good air quality levels inside a passive building, a periodic replacement is made depending on the number of people present and on the activity being carried out. The expected minimum replacement rate is 0.3 h-1, which means that one-third of the volume of air contained in the environment is exchanged in one hour.
For example, in a house of 120 m2 of surface, considering a fresh air requirement of 30 m3 / h per person, for a family of 4 people it is necessary 120 m3 / h of fresh air. Considering an air volume of 324 m3 (with a ceiling at 2.7 m) there will be a required replacement rate of 0.37 h-1.
Air exchange also depends on the use of the rooms. The rate, however, is adjustable so as to allow a number of exchanges suitable for the number of people present. The replacement rate also varies depending on the use of the rooms: in a bathroom a replacement of 40 m3 / h is required, while a kitchen requires 60 m3/h.

 The building casing represents a human “third skin”, a protection diaphragm between the inner and outer environment directly responsible for the overall well-being of the individual. The components that constitute the casing of a “passive house” (designed according to passivhaus principles) must meet certain performance requirements in order to ensure optimum levels of comfort in indoor environments.
To reduce heat exchanges between inside and outside, the thermal casing must have both a good thermal insulation and an effective air-tightness. Thermal insulation, on one side, guarantees the healthiness of the environments preventing surface condensation responsible for the formation of efflorescences and molds on the inner surface and, on the other side, ensures in winter time surface temperatures of the elements > 17 ° C with consequent reduction of heat exchanges by irradiation between the individual and the surrounding environment (thermo-hygrometric well-being). The heat-insulating layer also reduces summer building overheating.
The walls delimiting the heated volume are thus characterized by an external thermal insulation layer with thickness ranging from 20 to 35 cm depending on the climatic zone.
Window elements in a passive house are key element in the energy balance of the building: in winter they maximize the free solar inputs which positively balance the heat losses by transmission; in summer, however, the high thermal performance of the windows reduces the danger of overheating the premises.

Sezione verticale finestra 1,23 x 1,48 m certificata da Passive House Istitute con grafico dell’andamento delle isoterme – Descrizione: guscio in alluminio rinforzato con poliuretano riempito con termoschiuma poliuretanica Uf = 0,75 W/m2K – triplo vetro 4/12/4/12/4 Ug = 0,70 W/m2K – Uw = 0,79 W/m2K ψg = 0,032 W/mK (distanziatoreThermix) (Tratto da http://www.passiv.de)

Placing window elements to the south is the ideal choice for the proper functioning of the energy balance, since glass components receive southern solar radiation that in winter serves to cover most of the energy requirements of the passive building. In summer, the sun is high on the horizon, whereby the glass element receives the least amount of solar radiation (the beams have a greater incidence angle with the glass). In general, to the south, a glazed surface is designed to be 25-30% compared to the full facade. Windows with east or west orientation do not guarantee large solar allowances in winter, while greatly contributing to the overheating during the summer and consequently require effective shielding systems.
North is the most unfavorable energy orientation and therefore the windows must be as small as possible and small in size.
In order not to compromise the high performance of the window, it is of utmost importance not only to design the wall-mounting connections properly but to ensure proper assembly.
The casing of a passive house is also characterized by an effective air-tightness, which plays an important role in terms of energy saving and comfort in indoor environments.
A good air-tightness of the building reduces infiltration of the outside air inside the heated space, thus reducing energy losses due to convective air flow through the enclosure. Such fluxes cause both a significant reduction in the insulating power of the material and an excessive exchange of air, and in the presence of a mechanical ventilation system equipped with heat recovery, results in a decrease in the system’s efficiency since the heat contained in air-daught is not recovered.
During winter time the warm air inside the rooms tends to migrate, through the casing, to the outside. Hot air contains water vapor that in contact with cold surfaces can condense and create within stratigraphies, damaging accumulation that can cause mold and mushroom formation. The bigger the air draughts, the bigger the risks that such phenomenon may occur.
Cold air infiltrations caused by high air permeability are the cause of discomfort in indoor environments due to, for example, the reduction in surface temperatures (air stratification), the reduction in acoustic insulation, poor quality of indoor air (input of harmful external pollutants such as nitrogen and sulfur oxides, powders …)
A passive house is characterized by a high shear tightness proven by the Blower Door Test, a vacuum and overpressure test that ensures the compliance of the enclosure with certain requirements imposed by the passivhaus standard (n50 ≤ 0.6 h- 1) for air tightness.
Realizing a good air-tightness entails a meticulous design and an equally scrupulous installation.

The PassivHaus and the warm and Mediterranean climates

It is usually possible to limit the thermal loads in the South European countries to less than 15 kWh/m2/year without too much difficulty. Thus low loads become marginal compared to other home energy needs, such as domestic hot water, lighting and home appliances. The interesting result is that cooling loads can often be faced with only passive strategies, so it is possible to design, by adopting appropriate solutions, comfortable low energy homes that can often avoid the use of active cooling media.

The Italian Passivhaus arises from the premise that the design solutions commonly implemented for Central Europe Passivhauses, typically based on a large enclosure insulation, no thermal bridges and forced ventilation with heat recovery:

• Are reusable in the Italian areas characterized by relatively rigid winters, albeit brief, such as in Milan and, generally, in the whole North, but also in the mountain regions in the South;
• can, if integrated with additional solutions, provide an effective strategy for passive summer cooling.

The Italian Passivhaus has the following additional solutions:
• the shading of windows by means of grids or shutters to reduce solar gains;
• a night-time ventilation strategy, integrated in particularly hot days, by an active cooling system provided by a low power reversible heat pump.

The advantage of basing the Italian Passivhaus on the concepts applied in Central Europe lies in the fact that these concepts can be readily integrated into homes with commonly accepted aesthetics and layouts.
Simulations conducted with Dynamic Modeling Software (DOE energy-plus) have shown that with appropriate adaptations of the various design strategies (eg by varying the insulation layer of the building enclosure), it is possible to get comfortable conditions throughout the year in Milan, Rome and Palermo.

The strategy

Although the Italian Passivhaus adopts many of the concepts of the German one, some details have been modified. In general, the mildest climate in Italy allows to reach the energy and comfort limits of the Passivhaus standard by using less stringent criteria for:
• Insulation levels: a typical German Passivhaus requires 25-30 cm of insulation on the exterior walls and 35-40 cm on the roof. In Rome it is enough 10 cm of insulation on the wall and roof.
• Air-tightness of the casing: Central Europe’s standard and good practices require building casings to limit airflow to a maximum of 0.6 h-1 for a 50 Pa pressure difference (n50 < 0.6 h-1). But in Milan and Rome, the n50 limit of 1 h-1 should be acceptable, and even too conservative in Palermo.

In particular for the Winter Comfort the Italian Passivhaus:
• Minimizes winter heat losses thanks to a highly insulated casing and the elimination of thermal bridges.
• Provides forced ventilation with heat recovery from exhausted air.
• Provides active heating using a low power geothermal heat pump (maximum thermal load in winter and summer = 1.5 kW).
• It allows solar gains using the glass part (30%) of south facing surfaces and reduces leakage by limiting glass surfaces to the North.

While for Comfort Summer:
• It minimizes solar gains thanks to a highly insulated casing and window shading.
• It removes solar gains and indoor gains accumulated in building structures during the day using a hybrid (natural and forced) nighttime ventilation strategy.
In this regard it is noted that using a heavy and well-insulated structure, it is possible to obtain a suitable condition for the use of the summer natural nightly cooling of the building’s thermal mass. The night air is circulated through the building, by wind action or exploiting natural density gradients, or by using ventilators in the forced ventilation system.

strategie estive strategie invernali
Summer strategy
Winter strategy

Performance: energy and comfort

Summer comfort conditions in Milan and Rome can be assured with fully passive systems. More precisely:
• In Milan the upper limit of the Comfort Adaptive Temperature (according to EN 15251) is never exceeded, even though the thermal neutrality temperature is occasionally exceeded in August.
• In Rome the upper limit of Comfort Adaptive temperature has never been exceeded, but it is often exceeded by the neutrality temperature in August.

In any case, passive cooling entails maximum indoor temperatures of about 30 ° C both in Milan and Rome.

Even if the nighttime ventilation strategy is effective, indoor temperatures can be reduced using a small reversible heat pump. Modest energy consumption brings internal temperatures appreciably close to the neutrality temperature defined by the adaptive comfort model. (Maximum temperature of about 27.5 ° C).
In Palermo, the natural ventilation strategy is less effective and some form of active cooling is needed to ensure comfort conditions. In Palermo, the natural ventilation strategy is less effective due to the reduced daily temperature changes (on average only 3 ° C in summer). Active cooling is required to make the summer comfort conditions acceptable. By using purely passive systems the summer temperature reaches 32.5 ° C, which is the highest comfort temperature acceptable according to the adaptive model, mostly for August. Even with a significant active cooling (9 kWh / m2 / year), the neutrality temperature is exceeded for many days in August, although in general indoor temperatures are always lower than the maximum acceptable temperature.
Finally, the behavior of houses was examined during particularly hot summers, increasing the summer temperatures of 3 ° C. While in Milan and Rome there are comfortable conditions, in Palermo the internal temperature considerably overcomes the neutrality temperature, even with active cooling.

The north of France is somewhat similar to that of Germany, though slightly milder due to the influence of the Atlantic Ocean. Thus a Passivhaus in northern France could look like a Passivhaus in Germany: a good isolation of the building enclosure (typically from 25 to 40 cm of insulation) without appreciable thermal bridges, minimized air infiltration, an air delivery and extraction system with highly efficient heat recovery, windows with insulated frames and triple low-emissive glasses with gas in the cavity.
This allows a simplification of the mechanical system: the heat distribution system can be replaced by a centralized central heating unit that serves the entire home.
For two locations with Mediterranean climate in southern France, Nice and Carpentras, the Passivhaus proposal has been developed adapting these pèrinciples to the hottest climates in the South.
The layout of the house corresponds to a typical two-floors townhouse as it is being built in large numbers all over Europe, with an unheated basement, an open floor space and three bedrooms on the first floor. Houses are hypothesized south oriented, with the next row of houses located at a distance of 23 m.
For Carpentras, the insulation level can be reduced to 15 cm in the wall and roof and 8 cm to the basement floor. For the mild climate of Nice, it is already enough to use the level of insulation required by law. The reduction of thermal bridges is applied extensively, except for the supporting walls between basement and first floor. In particular, this corresponds to the use of external insulation, so that the inner walls and the ceiling have no significant effect on the thermal bridges when considering the external dimensions. For both locations, low emission double-glazeing with conventional frames was appropriate. Ventilation is also applied with heat recovery along with the reduction of infiltrations.
In Mediterranean mild climates , the same extremely low heating requirement can also be obtained with a traditional exhaust air system, but for example in Carpentras, this would require insulation thicknesses greater than 300 mm and insulated window frames.

The strategy

The average daily heat load is small enough to be covered by a simple mechanical pre-heating of the inlet air.
Radiators and a separate heat distribution system are no longer needed. The way heat is produced is not very important, but the use of electric heaters to heat should be avoided.
Given the small peak thermal load, the building services can be greatly simplified. This reduces overall investment costs and therefore justifies the greater investment for an efficient envelope. A significant reduction in cost can often be achieved by using compact units of heat pumps. These units use exhaust air downstream of the heat exchanger as a thermal source of the integrated heat pump. The heat pump also supplies hot water, accumulated in a tank. All services required by the building, ie heating, domestic hot water and ventilation, are integrated into a single unit with its control and regulation mechanism, which can be easily installed without the need of a refrigerant. No energy vectors are required to connect to the building, save electricity.
During the summer, the insulation of walls and roof helps to limit the solar loads entering the building. External shading accessories are required to minimize solar radiation through the windows. Since the average ambient temperature is below 25 ° C for most of the time, ventilation system heat recovery of the is bypassed during the cooling season.
The various cooling strategies differ depending on the location. Carpentras, thanks to low night temperatures and acceptable levels of specific humidity, a night air exchange with open windows is enough to ensure thermal comfort. In Nice, because of the high levels of moisture and the less pronounced daytime thermal excursion, inlet flow air is actively cooled if necessary, possibly even dehumidifying. It is technically possible to build compact heat pumps that also provide delivery of cooling inlet air, but are not currently commercially available.
Air exchange through mechanical ventilation is still determined according to the indoor air quality requirements. We hypothesize a modest natural ventilation, to take into account that users can open the windows when there are favorable external conditions.

strategie estive strategie invernali
Summer strategy
Winter strategy

Performance: energy and comfort

Both in Carpentras and Nice, the building’s annual heating requirement is slightly less than 15 kWh / m² year. Occasionally, in the sunny winter days, the internal temperature increases by 1 or 2 K above the set point of 20 ° C.
As described above, the examples of Nice and Carpentras follow several approaches for summer cooling. Carpentras, thanks to the concept of passive cooling, requires no energy to cool. Solar control and strong ventilation through the windows during favorable periods (nightly especially) keeps temperatures below 25 ° C for more than 99% of the year in all rooms. In Nice, a similar result is achieved by providing cool air and only a slight additional ventilation by opening the windows. In both cases, the resulting temperatures remain well below the summer adaptive temperature.
A thing that deserves further consideration is moisture. If above 12 g / kg, people start to feel discomfort regardless of temperature. In addition, relative humidity should remain between 30 and 70%.
In the case of Carpentras, it has been seen that these requirements can be guaranteed with passive cooling strategies over most of the time. The upper limit for relative humidity is exceeded for less than 4% of the year in all rooms. The period in which the absolute humidity limit is exceeded is even lower.
In Nice, however, the ambient air humidity is significantly higher than in the inland. If only temperatures were considered, passive cooling would be easily applicable in this climate, similar to Carpentras. Without dehumidification, however, both upper moisture limits would be exceeded by 13-15% of the year in all areas. Cooling the air and the corresponding dehumidification, on the other hand, provide comfortable conditions.

This analysis focused on the regional climate of Andalusia: Seville and Granada. Both resorts have a Mediterranean climate, but with peculiarities that make them more extreme and complex than other places like Cadiz or Almeria.
Seville has a very critical summer, while Granada has a hard winter.Moreover, it is intended to obtain housing that, under the new energy labeling rules, reaches the highest level (A is the best – E is the worst) with passive, low cost heating and cooling techniques and satisfactory comfort conditions as expressed In EN 15251.

The strategy

The environmental strategy for the Spanish Passivhaus example includes the elements described below.

Pre-heating of incoming air
A mechanical ventilation system (with very high air-tightness levels required for the building) is not taken into account since incompatible with the Spanish building characteristics.

The high glazing to the south maximizes the solar gains in winter. The main advantage of southern orientation, unlike the east and west, is that it has lower levels of summer solar radiation – when it is not desired; Moreover, it is easier to control the input. Control of solar radiation is obtained through movable shadings (see: “Glass and Solar Energy” in Part 2). On the north side, it is recommended to use the minimum glazed surface to meet the minimum natural light requirements. In places with severe winter conditions it is suggested to improve the U value of the glasses to the north.

Mass and thermal inertia.
Two solutions are proposed: low inertia with 6 cm traditional bricks towards the interior space, and high inertia with low density ceramic blocks.
High inertia is not applicable to Granada for structural considerations. In any case a high inertia solution should be used together with:
– Ventilation, that puts the air in contact with high inertia (high thermal mass) internal walls; The other walls do not need to have high inertia.
– Proper distribution of mass, so that solar radiation impacts on the massive walls.

Night ventilation
The staircase during the night acts as a chimney that allows air extraction during summer nights.

On the top of the stairs can be realized a long south-facing window, to allow the natural lighting of the north area.

strategie estive strategie invernali
Summer strategy
Winter strategy

Performance: energy and comfort

The total energy demand of the Seville house is 24.5 kWh / m2 (2.8kWh / m2 for heating, 21.7 kWh / m2 for cooling). This value does not meet the Passivhaus summer requirements. However, these values correspond to excellent levels in the national energy labeling (A for heating – B for cooling). The average total energy requirement for a new conventional house is 57.3 kWh / m2, the proposed Passivhaus project for Spain results in a 57% reduction in this value.
The total energy demand of the Granada house is 16.6 kWh / m2 (8.7 kWh / m2 for heating and 7.9 kWh / m2 for cooling). This value complies with Passivhaus requirements. The total average energy requirement for a new conventional house is 69.0 kWh / m2, so a 76% reduction was achieved on this value. This Passivhaus would have an energy label A for heating and B for cooling.

Passivhaus’s standard energy and comfort strategies have been adapted to the Portuguese context, particularly with regard to the long cooling season. The present proposal takes into account the local climate (case study for Lisbon), the construction standards, and the technical and economic context.
The insulation level of walls and roofs exceeds national standards, while air intakes are controlled (0.8 h-1 to 50 Pa). However, insulation and air tightness are not the main issues for the proposal under consideration. The three main aspects are: relationship with the Sun, cooling ventilation, high thermal mass to control temperature oscillations.
Sun availability is quite high in Portugal, even during the cold season. Thus a key factor in this home is the relationship with solar radiation, captured either directly (windows) or indirectly (solar thermal). Large windows are mainly south oriented to increase solar gains in the winter. Minor surfaces are oriented o the east and west, minimum to the north. Sunscreen is chosen depending on the orientation: overhangs for windows to the south to reduce the solar summer incidence, Venetian blinds in all windows.
A very important aspect is the use of solar thermal. The new Thermal Building Regulation requires the use of solar thermal to produce domestic hot water (provided it has a suitable exposure). The proposal extends the use of solar also to cover an important part of heating demand by increasing the area of solar panels and using a low temperature distribution system (eg radiant floors).
As proposed for the Passivhaus standard, the active heating and cooling capacity is limited to 10 W / m2.

The strategy

The house combines the ability to collect heat from the Sun (wide windows to the south) and the ability to adjust the internal temperature using its high thermal inertia.
To reduce leakage and heat gains, 150 mm and 100 mm insulation for roof and exterior walls were proposed, with U values of 0.23 W / m2K and 0.32 W / m2K respectively. Insulating the floor (80 mm) is beneficial in colder climates. But where cooling is prevalent in heating, only one 1m strip of the perimeter beneath the floor should be isolated so that the central core of the house can release the heat to the ground during the summer.
The south facing windows correspond to approximately 60% of the total window surface; approximately 20% of the window surface faces east, another 20% west. The house has dual low-emissive glasses that can be very effective in the colder climates of Portugal, but most often double normal glasses are more convenient (they are considered U of 2.9 W / m2K for normal double glazing and 1.9 W / M2K for low-emissivity).
Thermal solar cover most of the demand for home heating. The solar panels are installed southwards, tilt by 50º compared to the horizontal plane, to increase winter efficiency.
To avoid overheating during the summer season, especially in the rooms facing south and west, it is important to use solar control devices (blinds and overthrows) and combine high thermal inertia and ventilation, especially during night (the temperature of the air outside drops a lot during night time). High thermal inertia can be obtained by using heavy concrete floors with internal brick partitions and applying insulation to external walls and roof. But there is still skepticism among Portuguese makers on mechanical performance of the exterior insulation, so it is proposed to use the traditional double-brick wall with insulating layer in the gap.
An effective pass-through ventilation strategy can remove heat stored in the walls and floors. In the bedrooms, ventilation should take place in the evening, to avoid currents during the hours of sleep; In the other spaces you can use the cooling all night.
Effective solar control, coupled with a ventilation strategy that dissipates solar and indoor gains, can reduce the power required for active cooling or even making the installation superfluous.

Performance: energy and comfort

The annual heating energy demand for the Passivhaus proposed for Portugal has been estimated at 16.9 kWh / m2, of which 11 kWh / m2 is supplied with solar thermal (in this analysis the priority of solar thermal is given for heating, while the fraction of solar energy used for domestic hot water is 48%). The annual cooling energy requirement is 3.7 kWh / m2. The sum of the net demand for heating and cooling is 9.6 kWh / m2 year. According to the Heat Regulation, the heating and cooling limits for this house built in Lisbon are 73.5 and 32 kWh / m2 year respectively.
The thermal comfort analysis is based on the resulting temperature (or operational), the average of the air and radiant temperature.
The comfort criteria adopted during the summer survey were based on the calculation of comfort indices (see Part 2). The indices add up over the entire period the “distance” between the expected room temperature and neutral temperatures for each hour. So a low index value stands for a better performance.
The house with active cooling has a Fanger Comfort Index of 811 (the house is penalized by the influence of the radiant temperature of the large window area). If no active cooling is present, the Comfort Adaptive Index (AI2) is applied according to ASHRAE 55. For the Passivhaus proposed for Portugal the AI2 index was 16. For this house, the resulting temperature is kept below the 25 ° C for 71% of occupancy time, and below 28ºC for 98% of occupancy time. In the absence of active cooling systems, the window size and the thermal insulation of the walls should be reduced (although this latter action could increase the demand for heating).
In winter the low-power heating system (10 W / m2) is used, with which for only the 8% of the time the resulting temperature drops below 19.5ºC (the lowest resulting temperature is 18ºC).
The previous analysis shows how strategies to design a Passivhaus for the Lisbon climate can be winning, both in terms of energy and comfort limits. Although the specific design may be very different from the simple layout presented, the applied strategies have proved effective in their relationship with the climate.

The German Passivhaus’s energy and comfort standards were adapted to the English context, taking into account the local climate, construction standards, technical and economic framework, as well as the lifestyle and expectations of British property buyers as regards the use of space and interaction with the building. For example, one of the main features of the German Passivhaus is the mechanical ventilation system with heat recovery. For this to work, (that is, it involves net energy savings) the house must have a good air-tightness. But in the UK there is widespread skepticism among builders about the need for extremely sealed homes and the use of mechanical ventilation.
This is partly due to the milder winter climate and the perceived difficulty of reaching very low infiltration rates. Therefore, in the Sustainable Built Environments (SBE) proposal, ventilation is naturally obtained by means of low level (manually controlled) and high level (controlled automatically) openings. This has the benefit of avoiding capital costs and the maintenance of a mechanical system and allows occupants to have a degree of control over the opening of the windows. Air-tightness is still important, but the minimum airflow is fed through the bearing space by means of automated fans and ventilation vents.
The typical Passivhaus for example, follows the general layout of a traditional three-bedroom semi-detached cottage. The ground floor includes two ‘bearing spaces’ in the north and south. Even though they take away living space on the total floor surface, they can be used as temporary storage, greenhouses or laundry areas. The bearing space to the north also acts as the entrance lobby, while the south one is like a greenhouse included in the building’s volume. The other features of the British Passivhaus are the skylight at the top of the stairwell, which provides the exit for the chimney effect, and the automated openings with wing fans. There are about 300 mm of roof insulation and 200 mm on the wall. The glazed bearing area on the south side is furnished with Venetian blinds for summer sunlight and shutters isolated against winter heat losses

The strategy

The proposed environmental design strategy is a variant of the German Passivhaus strategy, combining natural ventilation with a high internal thermal capacity. In winter air supply is preheated through the south bearing space, which can reach temperatures up to 20 ° C. Where space allows, pipes can be installed in the garden ground for pre-heating (or pre-cooling) the air for the bearing space. The residual heating load is so low that it could be balanced with a “carbon neutral” source like a chips burner, which could also provide hot water. In summer, during hot days, the bearing space is opened outwards to avoid overheating and acts as an extension of the lived space. On summer nights, high-level automatic fan control will cool down the building and the indoor thermal mass. Safety is maintained using high-level automated ventilation skids and low-level fans.
The high internal thermal capacity can be achieved by facade-prefabricated concrete panels or, where lightweight construction is preferred, by PCM (phase change materials) encapsulated in the plasterboard. The high internal thermal capacity is important to avoid overheating and the need for cooling, which with the progress of global overheating will become a growing priority.
Therefore, the typical British Passivhaus avoids the use of active cooling by shadowing and natural ventilation coupled with exposed thermal mass.
To minimize transmission and infiltration losses, high insulation levels with typical U values ranged from 0.2 W / m2K to 0.15 W / m2K, respectively for walls and roof have been used. Double low emissive glasses (not triple glasses as in the German Passivhaus) are offered for internal glazing surfaces, while the outer layer of the bearing space has simple glasses. The outer layer may also be double glazed, which could improve the performance substantially, but it has been demonstrated using simulations that the standard required for heating is achieved with the glazing described above. Typical U values of 1.8 W / m2K for windows are assumed, while infiltration rates are equal to 3 50 Pa hourly spare parts.

strategie estive strategie invernali
Summer strategy
Winter strategy

Performance: energy and comfort

The annual energy demand for the heating in a British Passivhaus as proposed by SBE was estimated at a total of 13.8 kWh / m2.
This value complies with the Passivhaus standard of 15 kWh / m2, and is to be compared with a typical annual energy demand for heating for the same house built with the current building rules of 55 kWh / m2. No active cooling is required due to the passive mitigation strategies described above. It should be remembered that this is a front-facing villa, and therefore a rowhouse with the same layout could get these performances with slightly reduced specifications.
The comfort criteria adopted during the summer test were based on the calculation of comfort indices These indices add the “distance” between the room’s operating temperature and the neutral temperatures every hour on the whole year. The Adaptive Comfort Index (AI2), applied to “free running” buildings (ie without additional heating and cooling), refers to a neutral comfort temperature defined on the basis of the Monthly Adaptive Models reported in ASHRAE 55. When evaluating comfort using this index, a low value indicates a better performance, since zero is the optimal performance. For the Passivhaus proposed for the UK, the AI2 index was zero. Concerning summer temperature conditions, the resulting (or operating) temperature, which is average between the air temperature and the radiant temperature, is kept below 25 ° C for 96% of the occupancy time . In winter the indoor air temperature is kept at 20 ° C by means of traditional heating to meet the residual demand for heating. But in the absence of an additional heating system, the percentage of time in which the internal temperature inside exceeds 18 ° C, is 68%. In the lived area the resulting temperatures typically fluctuate between 10 and 24 ° C, exceeding the ambient temperature of 5 – 15 ° C.
That said, the strategy adopted for the design of the house succeeds in guaranteeing the Passivhaus standard in terms of heating / cooling requirements and thermal comfort. It also reveals that it is not necessary that the strategies required to achieve those benefits are prescriptive. This will provide both designers and builders with greater flexibility when choosing between the different priorities for a reliable passive home.

lightbox title

Contact us!

Buy your Passivhaus!

Contact us for any information and subscribe to our mailing list Keep up to date with all the latest news!

  • Conferences
  • Courses
  • Passivhaus Days
  • Insights

  • Information