Passive houses

Passive houses are the houses that ensure a comfortable indoor climate in summer and winter, but without the need for a conventional heating source.
To be possible, the annual requirement for heating a building should not exceed 15 kWh / (m² * year). Minimum requirement may be achieved by heating the air supplied by the ventilation system – a system that can be implemented in any case.
A European standard is called PASSIVE HOUSE because the passive energy from solar radiation is trapped outside and then provides the heat for some home appliances, and for occupants is enough to keep the house at a comfortable ambiental temperature in cold weather. A component of the passive house concept is that efficient technologies are used to minimize power consumption from other sources (notably – electricity for household appliances). The objective is to maintain a total consumption of heat, hot water and electricity, below 42 kWh / (m² * year).
Criteria for passive houses per square meter of living area:
- Up to 10 Wh / m constant caloric
- Up to 15 kWh / m² required annual space heating
- Maximum 42 kWh / sqm total annual energy consumption required

How to build a passive house

To not spend money to heat the house is a very attractive concept. To achieve this high level of performance you expect to substantially increase construction costs, right? Well, costs are not excessive as long as architecture and orientation of the house are made with careful planning!

Some general issues concerning architecture:
- To consider a compact type with a small footprint
- Large windows to the south, no window oriented to north
- Fewer exterior doors
- Half a roof just to the south (solar panels)
- To consider building a single wing
- To consider building a duplex with two or more apartments in a single building.

Passive house architecture may differ, but the principle remains the same. The principle behind passive houses is based on a concept – to reduce house investment through efficient design fom the energy point of view. If substantially simplified, air-conditioning systems increase energy efficiency so that a building can achieve a high level of efficiency.

Consider the following example: you need to built a house in a cold climate area. Energy requirement is higher to heat the house in the winter. If you reduce your caloric intake by thermal insulation of the building and use insulated windows (with classic windows 40% of heat is lost), passive solar systems and other methods can increase thermal efficiency, thus maintaining ambient temperature. Thus, the heating system can be simplified step by step. But the most significant step occurs when caloric needs reach a maximum of 10 Wh / m. When maximum caloric need is less than 10 Wh / m, regardless of climate and season, the ventilation system can be used for space heating, thus eliminating the need for a separate heating system.

The main function of a ventilation system is to maintain excellent indoor air quality. If the energy requirement is less than 10 Wh / m², ventilation system has to distribute all the heat required in the building. Therefore, the definition for passive house is designed for maximum caloric requirements under 10 Wh / m. In warmer climates, this value can be achieved very easily, compared to cold climates.

Increasing energy efficiency below the threshold of 10 Wh / m² brings no additional benefit. Construction costs increase dramatically if we want to build a house with zero energy consumption, instead of a passive house. Similarly, a house with zero energy consumption will not be beneficial either for the environment, beside a passive house. Passive houses have a very low caloric need to maintain indoor comfort in cold weather. The heat demand is so small that the environmental impact is negligible even if fossil fuel (oil, gas, coal) is used as energy source.