What a passive house is ?
A passive house consumes 90% less energy than a habitual house and even a 75% less than a new house (built to the European standards). The energy consumption of a passive house corresponds to 1.5 l/sq m/year of petroleum equivalent and it is more reduced than the consumption of an energetic efficient house (at the European standards). The comfort of the house is however the highest one. The passive house takes maximum advantage of all the available heat resources, like the body or the sun heat, which reduces the need of essential energy for heating. Particularly, the windows and the casing (that are the components of an extremely efficient insulation of the external walls, roof and ground) make possible the internal warm keeping. The fresh air, without streams, it is provided by a controlled mechanical ventilation system that recovers the heat of the evacuated air and returns it inside the house.
- The passive house is truly energetically efficient, comfortable, affordable and ecological.
- The passive house it is not a trade mark but a concept, a new way of building.
The passive house. Comfort by efficiency
The passive house is the top concept in the energetic efficient constructions subject; the energy saving for heating is of 75/80% compared to a newly built house according to the law in force (European standards). The necessity of energy for heating being below 15 kw/h/sq m/year, generates costs of 10-25€/month, which makes the energy price oscillation unimportant for a passive house. These houses reach an enormous energy economy thanks to some particular efficient components and to intelligent ventilation. However, the comfort is optimized and not diminished. The passive house is more than an energy saving house, is a global concept for building quality, healthy and durable houses. This concept can be easily understood by everyone.
- Today’s new constructions and those in restoration, every time they get more insulated and air tight, generate true ventilation deficiencies by eliminating the cracks and the imperfect joining. Neither the "ventilation through the open windows" is energetically satisfying. The fresh air is not only a matter of comfort, but also a requirement for a healthy life. That is why the ventilation of a home is one of the essential techniques for the future constructions.
- It is also true that a controlled mechanical ventilation system has a higher price, but if it is built efficiently this system generates important savings. The ventilations systems with the "passive home" label are guaranteed profitable.
- The interesting particularity of the passive house concept is the presence of the fresh air in every room; if this is used for heating - in a reasonable quantity, without uncontrolled circulation, without noise and streams - then the ventilation system is twice profitable.
- The idea of the “fresh heated air" is possible only in very well insulated and air tight buildings like the passive house. For the experts: the energy requirement for heating must be below 10 W/sq m (functional sq m) if you want to use the ventilated air stream for the building heating. The passive house supposes performance in terms of: insulation, construction without thermal bridges, air tightness, and ventilation with heat recovery, windows and innovating techniques.
STANDARDS
The passive houses are constructions that ensure a comfortable internal climate both in summer and winter without resorting to a conventional system of heating or cooling. In order that be feasible it is necessary that in our climate conditions the need of heating energy not to exceed 15kWh/sqm/year. This corresponds to a heating installation with a maximum power of 10W/sqm. This reduced necessity of heating can be sustained by the ventilation system that is anyway indispensable to guarantee the hygiene and the quality of the air. That means that a passive house need a 80% less energy for heating than a classic system built house, according to the law in force (European standard). “The passive house” term was mainly choose because the passive use of the environmental energies (solar radiation through the windows) and internal heating sources (domestic appliance and habitants) are enough to maintain inside the building a pleasant temperature all over the year.
The passive house standards offer an interesting way of reducing at minimum the energetic demand of the new constructions, thus reaching the objective of the lastingness and improving the comfort of the habitants. This minimum of the energy necessity may be exclusively satisfied of renewable resources.
The two main principles of a passive house are:
1. Basic conditions optimization
We improve the performance of the indispensable components of a passive house: the building envelope, the windows and the ventilation. The thermal efficiency of these components is improved so there is no need of a conventional heating system anymore. The main resource is the vitiated air recovery.
2. The maximum reduction of loss
The available heat in a house is kept inside so efficiently by very good air tightening. The calculations realized according to theoretical models and many already built examples prove that in the varied conditions of the European climate, a strategy focused mainly on the heat waste reduction is more efficient than a strategy centred mainly on the active or passive use of solar energy. “The essential aspect does not consist in the way of heating but in waste. We would rather warm a well insulated house with coal than use solar energy for a store room.” (Norbert Egli – Swiss Agency for the Environment, Forests and Landscape)
PRESENTATION
1. Energy consumption
- The heat
| Objetive | The reduction of the used energy consumption for heating. |
| Standar | Required energy for heating ≤ 15 kWh/sqm/year |
- Total energy
| Objective | The reduction of the used energy consumption inside the house (heating, ventilation, warm water, domestic appliance, etc.) |
| Recommendation | Total energy requirement ≤ 42 kWh/sqm/year |
- Primary energy
| Objective | The reduction of the primary energy consumption inside the house (the efficient election of the used energy type) |
| Recommendation | Required primary energy ≤ 120 kWh/sqm/year |
2. The solar energy
- The solar energy
| Objective | Optimal southern orientation (if possible) for the maximum caching of the free solar energy |
| Recommendation | Approximately a 40% from the necessary heat for the building energy waste compensation. |
- Competitive windows
| Objective | Triple-pane Low-e window or the equivalent. |
| Standard | Coefficient U window ≤ 0,8 W/sqmK Transmittance factor (g) > 50% for the solar supply through the window be superior to the waste. |
- Competitive windows
| Objective | Perfect insulated frame (thermal bridges avoiding) |
| Standard | Coefficient U frame ≤ 0,8 W/m²K |
3. Insulation
- Envelope (light tight sides)
| Objective | Extremely efficient insulation in order to renounce to a conventional heating system (the thickness of the insulation: 20-30 cm at the ground, 3—40 cm at the wall, 40-50 cm at the roof) |
| Standard | Coefficient U ≤ 0,15 W/sqmK |
| Recommendation | Coefficient U ≤ 0,11 W/sqmK |
- The connection
| Objective | Without thermal bridges |
| Standard | Lineal transmittance coefficient y ≤ 0,01 W/mK |
- The air tightness
| Ojective | Tight envelope The use of the tight doors and/or frames. |
| Standard | Air refreshing for n 50 < 0.6 h-1 according to NBN EN 13829 |
4. The heat recovery
- Ventilation
| Objective | Controlled mechanical ventilation. Air blast in the intensively used area (dinning room, bedrooms, etc.), recovery from “wet” spaces (bathroom, kitchen, etc) |
| Standard | 30 sqm/h/person |
| Recommendation | Adjustment according to the air pollution. |
- The heat recovery
| Objective | Air-air changer: the heat recovery from the vitiate air (without contact between the two flows) |
| Standard | Actual efficiency more than an 80%. |
- Air-ground changer
| Objective | The fresh air preheating in the very cold days and the passive cooling of the fresh air in the very warm days with a Canadian put. |
| Standard | The new air temperature > 0°C |
| Recomandare | Temperature increments (ΔT) > 8°C |
5. The electricity
| Ojective | The use of the efficient domestic appliance (A class), economical bulbs, etc. 50% of the electrical consumption might be possible without the comfort diminishing. |
6. The additional energy
| Objective | Due to the reduced energy requirements, this can be produced and sustained by renewable resources. |
ARGUMENTS
Economic argument
When it comes about building passive homes, this first question arises: Is it more expensive than a classic one? The German and Austrian experience in the passive homes construction field shows that they are not significantly more expensive than conventional ones.
On one side, there are some extra costs (additional thermal insulation, special thermo frames for the windows, special triple glazed window, special air conditioned and perfect insulation of the all around envelope) which are actually compensated by the savings obtained by the elimination of the heating system and all its connected labour. On the other side, the bill for energy will be up to 10 (ten) times lower than the bill for a conventional home built on standards in force now.
The Germans, the Austrians, the Scandinavians, and recently most of the European countries are on their ways to implement with great success this new standard and are about to build passive homes a prices not exceeding 15% the costs of a conventional home, based on the complexity of the project. Comparing these data and further benefits of a significantly reduced energy consumption, the advantage inclines undoubtedly in favour of the passive home. Another important element: the building time of the house is shortened, so that the investment is recovered faster than in the case of classic constructions and the amount of workload reduces significantly.
According to European studies, the total costs of a passive construction, capitalized over 30 years (design, building, equipments, operating costs) is far inferior to those of a conventional construction of equivalent type.
Conclusion says that in terms of building and operation costs the passive one is extremely profitable.
Ecological argument
There are vital advantages for the health and comfort of the inhabitants, such as:
Substantial diminishing of the carbon emissions, the use of ecological raw materials, the outstanding comfort provided by the fresh air in the house, the absence of cold surfaces in wintertime and excessive heat in summertime, the absence of the allergenic dust, the maximal daylight lighting, the lack of stress induced by the excellent integration into the natural environment, etc.
The quality of the raw materials, the absence of craft flaws, the lack of excessive humidity are factors that help extending the lifespan of the construction compared to the classic homes.
It is difficult to compute all these factors together, but it is obvious that they have a major impact on the lives of those who choose to live in a passive home.
Certain contextual repetitions are meant to increase the concept understanding.