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8. Passive houses

The dwellings in the village of Abitare la Natura provide thermal well-being without or with a minimal source of energy for heating inside the building or without any “traditional” heating system, i.e. boiler and radiators or similar systems. Thus, it is a house with maximum energy eciency. It is called “passive” because the sum of the passive thermal contribution of the solar radiation transmitted by the windows and the heat generated inside the building by the appliances and the occupants themselves is almost sucient to compensate for the loss of the shell during the cold season.
Thus, passive architecture is an architecture that uses a number of passive devices to cover most of the energy needs of buildings due to the heat and cold ows extracted from the external environment. Since, at any time of the year, the cold and heat outside are not always available when they are useful, it uses “heat accumulator masses”, that is, quantities of materials with high heat capacity (= specic heat capacity x mass). Given that building materials have a specic heat capacity that is not very dierent from each other (about ± 20% of the average value), traditional heavy materials (such as stone, concrete, brick) or new concept materials ( such as phase transition materials from PCM) are used to produce ecient heat accumulators, in rare cases also in water tanks.
These materials must be exposed to the internal environment in order to best perform their function of storing and releasing heat and cold, or, at best, separated from them by layers of materials with high thermal conductivity that are completely attached to them.
Passive buildings can be made of any building material: structural wood, brick, reinforced concrete.
A passive amplication system is a device for heating the environment and can be classied as “passive” if it is able to heat the building that is equipped with it, without requiring external energy sources.

Examples of passive devices for winter heating are, for example, solar greenhouses, storage walls, solar thermal water or air collectors, if they have natural circulation, as well as simple south-facing windows that can provide positive energy to the building, taking into account contributions throughout the year.

The definition of a passive environmental cooling device is more complex. For cooling, machines are available that usually require a larger amount of primary energy for the same amount of heat treated than heating machines.

For this reason, a cooling device is considered passive, even if it requires pumps, fans, or other auxiliary devices, if it does not use cooling cycles.

The energy needed to equalize the building’s thermal balance is usually supplied with non- traditional systems (for example, photovoltaic solar panels, thermal solar panels, or heat pumps to heat the air of a regulated ventilation system for energy recovery). A conventional heating system can be excluded if the heat load required for heating in winter is very small, usually less than 10 W / m2.

These characteristics are achieved with very careful design, especially for thermal bridges, with thick layers of thermal insulation materials around the perimeter of the walls, roof and lower oors, as well as through the use of controlled ventilation systems with energy recovery to minimize heat dissipation.

A passive home often requires a (low) percentage of energy demand that the structural elements and passive components of the home cannot meet.

To meet this demand, only sustainable ecosystems with renewable energy are accepted, which can be obtained from land, air, water, and the sun to make them work in synergy. At best, they will reduce your current expenses to 0.60-1 euro per day!

SOLAR SYSTEMS

On the roof of a passive house there is a solar system with two types of panels:
- thermal solar panels that use solar radiation to produce free hot water for both sanitary purposes and, if necessary, for a radiant panel heating system.
- Photovoltaic panels that convert solar radiation into free electricity to power the heat pump, VMC system, home lighting, and home appliances: a passive home can achieve energy self-suciency by completely zeroing out the bill.

RAINWATER HARVESTING

Where there is a passive house, rain is always welcome, because there is always a system of collecting (through gutters and drains), storing and annually processing rainwater for its reception.
A real water supply system, parallel to the sanitary one, which, with separate pipes, can only be used for irrigation of plants and gardens, washing oors or cars, as well as supplying water to the washing machine and sewer (not for drinking or hygienic purposes, such as showers or swimming pools).
During periods of drought, the control unit temporarily supplies the tank with tap water to avoid unpleasant odors caused by stagnant water at the bottom of the tank.

MECHANICAL VENTILATION

Ventilation of the premises is important for a comfortable stay, as it provides an exchange of air; it extracts musty air and introduces external, ltered from dust and from pollen.
The controlled mechanical ventilation system (passive house) becomes a part of the internal environmentcand integrates with the structure of the building, forming a single system of the building and structure, incwhich the developed and adopted technological solution strengthens the function of the enclosing building as an intermediary with the environment to create a comfortable internal microclimate for a person, exible and suitable for various activities that can be carried out in it.
Indoor air pollution is not limited to biological pollution caused by the metabolic activities of humans and animals (production of carbon dioxide, organic compounds, and water vapor), but also to chemical pollution caused by harmful substances contained in the building. materials and furniture, as well as re and physical re caused by the presence of ionizing and non-ionizing radiation and humidity.
The consequences of this exposure cause, in addition to a number of well-dened pathologies, such as asthma, allergies, and bronchitis, the most dicult to identify consequences for human health, which may be associated with a general sense of psychological discomfort and physical discomfort 2 to lack of concentration.