Passive House-Prefabricated houses

What is a passive house?

A passive building is a building in which internal thermal comfort (ISO 7730) is ensured exclusively by preheating or pre-cooling the amount of fresh air required (DIN 1946) for the correct indoor atmosphere, without the use of additional air recirculation. The passive building it is a building model which simultaneously offers high energy efficiency (energy house), comfort, economy and is environmentally friendly. The Passive House it's not a brand, but a design philosophy which is open to everyone and this has been proven in practice. Therefore, the passive house and building are more than just an energy efficient building or a simple energy house. The company KOFINAS, an official member of the Passive House Institute, is able to implement certified passive design constructions, offering you all the benefits combined with the high quality of the company's materials and construction!

Efficiency

Regardless of climate or region, Passive Houses maintain a comfortable and pleasant temperature all year round with minimal energy requirementsThe buildings are passively heated, meaning they make efficient use of the sun, internal heat sources and heat recovery, resulting in conventional heating systems not to be necessary even on the coldest days of winter. During the summer, a Passive House building uses passive cooling techniques, such as the correct design of shading and nighttime natural ventilation, in order to keep it cool. In any case, the excellent quality and technology materials and the careful design guarantee that the temperatures they remain all year round, at stable and pleasant levels for residents/users.

Viability

A Passive House uses up to 90% less energy for heating and cooling than conventional buildings in Central Europe, resulting in less than 1.5 liters of oil or 1.5 cubic meters of natural gas per year being required to heat one square meter of habitable space. However, extremely large savings are also achieved in warmer regions, where buildings need cooling. Reducing energy use leads to limiting greenhouse gas emissions, and so the Passive House is a truly sustainable choice compared to conventional constructions.

Economy

As has been proven by the way buildings operate (i.e. the only way to determine the real cost of a building), the operation of Passive Buildings has reduced expense requirements, while at the same time their construction cost is surprisingly affordableThe investment in high-quality construction materials, based on the specifications of the Passive House Standard, is balanced by the absence of the need to purchase conventional cooling and heating systems. In addition, this investment in energy savings is much cheaper and more efficient in the long run from unilateral investment in RES or the easy solution of fuel change.

Comfort

Passive Houses succeed thermal comfort space with very low energy requirements. Mechanical ventilation systems with energy recovery continuously provide the required clean air, offering excellent quality atmosphere, without being noticed due to reduced operating noise levels. The combination of stable temperatures and proper air exchange prevents moisture damage and mold growth.

Source: Hellenic Passive House Institute
How it works
The strategy of a passive building is to reuse of “free” heat for heating the house.

This “free” heat is produced by all electrical appliances, such as ovens, refrigerators, computers, light bulbs, etc. The building shell of a passive house must be very good insulated and airtight, so that this "free" heat does not leave the interior of the house unexploited.

1 Insulation

A properly insulated building shell, during the winter, retains heat inside the building, while in the summer it prevents it from entering it.

2 Windows

Properly designed, insulated and installed frames participate in the optimal utilization of solar gains.

3 Ventilation with Energy Recovery

Passive Building ventilation systems provide clean air, free from pollen and dust, with maximum energy efficiency through heat recovery and humidity control.

4 Airtightness

Passive buildings are designed to avoid air leaks in the building envelope, thereby increasing energy efficiency and preventing the occurrence of drafts and moisture damage.

5 Thermal bridges

Minimizing thermal bridges and weak points in the building envelope contributes to the creation of a pleasant and stable temperature, while eliminating moisture damage and increasing energy efficiency.

Shading, Nighttime Natural Ventilation, Light Geothermal Air and Proper Design of Thermal Mass contribute to the best performance of passive buildings in Mediterranean climates.

So, descriptively what happens is this:
A mechanical ventilation system with one heat exchanger air - air, is installed so that it can simultaneously bring fresh air and subtract a corresponding amount stale air.

In winter the cold outside fresh air enters the exchanger, receives the heat of the waste heat stale air and enters the house.

In the summer the exported stale air cools the hottest incoming fresh air.

In winter the warm stale air leaving the house, "brings" the "free" heat, which through the exchanger heats the fresh air that enters the house. Correspondingly, in the summer the cold stale air will cool the hot one in the exchanger fresh air.

In case the above system is combined with geothermal energy (the fresh air to be dissipated first by the earth and then go to the exchanger,) the profits in both winter and summer are multiplied.

The installation of a conventional heating and cooling system can be avoided.
Costs and profits

Indicatively, the cost of a 100 sq m passive house is 10% larger from a typical house of our company. This additional cost is negligible if one compares it to the energy saving that we achieve with a passive house. Not only will we pay for it immediately, but we will benefit significantly since the annual energy needs of a passive house are negligible.

What benefits does one get from implementing a passive house?

The benefits are multiple – there is great energy savings, which translates into reduced costs. The house's cooling and heating needs are zero. Moreover, in a passive house the quality of life improves vertically, since the stable temperature conditions and the continuous renewal of inhaled air have a positive impact on the health and well-being of the residents. Finally, the house is more practical during living, since it does not require the resident to constantly intervene to cool, heat and ventilate the house.

In the following diagram we see an energy balance of such a residence in diagram form:

And what does this mean practically?

It is, therefore, obvious that a passive construction is able to reduce operating costs to a huge extent of a residence, since – practically – it does not require any energy for cooling and heating.