What is a passive house
A passive building is a building where the indoor thermal comfort (ISO 7730) is ensured solely by preheating or precooling of the quantity of fresh air required (DIN 1946) for the “correct” inner atmosphere without the use of additional air recirculation.A passive building is a building model which offers high energy efficiency (energy house), comfort, economy and is environmentally friendly, alltogether. The passive building is not a brand, but a design concept that is open to everyone and has been proven in practice. Therefore, a passive house or building is more than “just” an energy efficient building or just an energy efficient house. Kofinas company, an official member of the Institute of Passive Building, is able to realize certified passive building designs, giving you all the benefits combined with the high quality materials and the construction quality of the company!
Regardless of climate or region, Passive Buildings maintain a pleasant temperature with minimal energy requirements throughout the year. The buildings are heated passively, effectively using of the sun, internal heat sources and heat recovery, so that conventional heating systems are not necessary even during the coldest winter days. During summer, passive houses – buildings use passive cooling techniques , as is the correct shading design and nighttime natural ventilation to keep cool. In any case, the high quality materials, the technology and careful planning guarantee that temperatures remain constant throughout the year, in a stable and pleasant for residents / users level.
A Passive Building uses up to 90% less energy for heating and cooling than a conventional building of Central Europe, and requires less than 1.5 liters of oil or 1.5 cubic meter of gas per year, for heating one square meter of living space. Additional economy is achieved in warmer regions, where buildings require cooling. Limiting energy use leads to reduced greenhouse gas emissions , so the Passive Building is a real sustainable option compared with conventional constructions.
Proven by the way a building functions (which is the only way of determining the actual cost of a building), the operation of Passive Building has reduced cost requirements , while construction costs are amazingly affordable. Investing in high-quality materials, according to the standards of the Passive House, is balanced by the absence of the need for conventional heating and cooling systems. In addition, this investment in energy savings is cheaper and more efficient in the long term compared to the unilateral investment in renewable sources or the easy solution of “fuel switching”.
Passive houses achieve thermal comfort with very low energy requirements. Mechanical ventilation with an energy recovery system, provide the required fresh air, offering high quality air , without being perceived by the habitants due to reduced operating noise level. The combination of constant temperatures and proper air exchange prevent damage from moisture and mold growth.
Source: Hellenic Passive House Institute
How does it work
The main strategy of a passive building is reusing the “free” energy in order to heat the house.
This “free” energy is produced by all the electrical appliances, like stoves, refridgerators, computers, lamps etc. The building shell of a passive house has to be really well insulated and airtight, so that this “free” energy does not leave the interior of the house unused.
- 1 Thermal insulation
- A correctly insulated shell, during the winter, maintains the heat inside the building, while during the summer it prevents the heat to enter the house.
- 2 Passive house windows
- The correctly designed, insulated and installed frames participate in the best usage of solar gains.
- 3 Heat recovery ventilation
- The ventilation systems of passive buildings offer clean air, free of pollen and dust, with maximum energy efficiency through heat recovery and humidity control.
- 4 Air tightness
- Passive buildings are designed to avoid air leaks in the building shell, thus increasing energy efficiency and preventing the occurrence of drafts and damage from moisture.
- 5 Absence of thermal bridges
- Minimising thermal bridges and weaknesses in the building shell, contributes to creating a pleasant and constant temperature and eliminates damage from moisture while increasing energy efficiency.
Shading, natural night ventilation, air geothermal systems and correct design of thermal mass contribute to better performance of passive buildings in Mediterranean climates.
As a result, we can describe what is happening as follows:
- A mechanical ventilation system with an air to air heat exchanger is installed so that it can simultaneously bring fresh air and remove a corresponding amount of stale air.
- The warm stale air that leaves the house, “carries” the “free” heat, which through the exchanger moves to the fresh air which enters the house.
- The cool external fresh air enters the exchanger, receives the heat of the rejected stale air and enters the house during the winter months, while during the summer the rejected stale air cools the – warmer – incoming fresh air.
- In case the above system is combined with a geothermal setup (the fresh air first passes through ground heat exchangers,) the benefits both during winter and during summer are multiplied.
- The cost of an expensive conventional heating/cooling system can be avoided and economic benefits can be attributed to better insulation, improved airtightness, window frames, ventilation system and an economic backup heating system..
Gains and savings
An indicative cost of a 100 sq.m. passive house is 10 % larger than a standard house of our company. This extra cost is negligible, taking into consideration the annual passive house energy savings.
What benefits can someone have from the implementation of a passive house?
The benefits are numerous – there are great energy savings, which translate into reduced costs. The improved quality of life is another advantage, since constant temperature conditions and the constant renewal of the atmosphere have a positive impact on the health and wellbeing of residents. Finally, the house is easier to live in, since it does not require for the residents to continually intervene for the cooling, the heating and the ventilation of the house.
In the following chart we can see an energy balance of such a house in chart form:
And what does this practically mean?
It is therefore obvious that a passive construction, is able to enormously reduce the usage costs of a house, since – practically – it requires no energy for cooling and heating.