Definition of Passive House

The objective of a passive house is to minimise the energy need of buildings economically and produce a good microclimate in buildings. The heat loss of a passive house is so small that a normal heat distribution system will be unnecessary. The initial investment in a passive house may be larger than in a normal house, but the operating and life cycle expenses will be remarkably lower than in a normal house.

The level of thermal insulation in structures is better than in normal low-energy houses. The structures are designed and built without any cold bridges that reduce heat insulation. The building’s outer shell is air-tight and the microclimate is draught-free and evenly warm. The high annual utilisation rate of heat recovery in ventilation guarantees only minor heat losses in ventilation. The remaining small energy need for heating can be covered using simple building system solutions.
 

Paroc Concept solutions for passive houses

In Paroc Oy Ab’s development project Paroc Passive House for Nordic and Baltic Housing Market, a concept solution and model house were developed for the cold climate. The development work utilised the requirements for passive houses in cold climates developed in the Promotion of European Passive Houses project (http://www.europeanpassivehouses.org) of the European IEE (Intelligent Energy Europe) programme. The principle of the concept solution is to transfer buildings’ investment costs from the building systems to the improved thermal insulation in buildings’ outer shells. When the heating energy need in a building is small enough, the traditional heat distribution method based on floor heating and radiators can be replaced with simpler ventilation. Because the building has mechanical ventilation equipped with heat intakes, the ventilation system can also act as the building’s heat distribution solution. The change in the building system solution will have an effect on the building’s investment and life cycle costs.

Passive houses are defined on the basis of their energy need. Thermal insulation of the outer shell and its parts, air tightness of structures and the annual efficiency rate of heat recovery of ventilation are the means required to achieve the requirements for the heating energy need referred to in the definition. In addition, the need is affected by the relationship between the area of the building’s outer shell and its volume, i.e. the shape of the building.
 
A passive house is based on technology that does not depend on the utilisation of solar energy. Good thermal insulation, air tightness in the outer shell, low-energy windows and doors and heat recovery from exhaust air constitute the bases of a passive house. Even though the orientation of buildings towards south produces energy benefits, experiences in passive houses in central Europe prove that the concept is functional in building sites facing north. The principle makes it possible to utilise the landscape well in design.

The limits of the energy need for heating are suggestive. The objective is to develop one house solution which would be suitable as a passive house throughout the country. The passive house definitions applied in different parts of Europe are based on the preliminary energy need requirements presented in the Promotion of European Passive Houses PEP and Passive-on studies of the Intelligent Energy Europe research programme:

Warm climates in Southern Europe

•     Need for heating energy: 15 kWh/m2
•     Need for cooling energy: 15 kWh/m2
•     Need for primary energy: 120 kWh/m2

Central, Eastern and Western Europe

•     Need for heating and cooling energy: 15 kWh/m2
•     Need for primary energy: 120 kWh/m2

Nordic countries north of latitude 60°

•     Need for heating and cooling energy is 20-30 kWh/m2 depending on the location of the building
•     Need for primary energy: 130-140 kWh/m2
•     The building’s air leakage coefficient n50 < 0.6 1/h in all climates

 
The definition of a passive house is based on its energy need. The building’s total energy need is estimated in primary energy and it has limit values. The problem of primary energy is the lack of clear estimation means. For example the German PassivHaus Insitut proposes a primary energy conversion factor of 2.7 for all electric energy bought from the electric grid. However, this does not encourage the acquiring of electric energy based on renewable energy sources. The energy conversion factors are always agreed on the national basis.