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Research Group for Cost-effective Passive Houses - Phase I: 1996 till 1998

Carried out on behalf of:

Monitoring of the construction of second-generation Passive Houses
Experiences with the first inhabited Passive Houses were so impressive that it was possible to introduce this building standard with a separate heating system in the following years. The results from projects relating to cost-saving construction were also incorporated so that second-generation Passive Houses would become cost-effective residential buildings without a heating system.

The Research Group was entrusted with the task of monitoring and providing technical assistance for planning and construction of Passive Houses. It was intended to constitute a link between the project teams for specific building construction projects, technical component development, and scientific monitoring by the Passive House Institute (PHI).

The first phase of the Research Group ended, but was continued in another form.

Passive Houses are buildings with an excellent standard of thermal protection which do not require a heating system.

Experience with energy-efficient construction has shown that there will be two inherently consistent, coherent concepts for energy-efficient buildings in the future:

The low-energy house,
in which it is possible to achieve a specific heating demand between 30 and 70 kWh/(m²a) due to the good level of thermal protection, insulating glazing and an economical exhaust air ventilation system. However, such a house still needs a conventional hot water-based heating system for several reasons.

The Passive House (PH),
in which a specific heating demand of <15 kWh/(m²a) is possible due to even better thermal protection, low-e triple glazing, and a supply air/extract air ventilation system with highly efficient heat recovery. Dispensing with a conventional heating system is possible under these conditions. All of the measures mentioned are established technology that is also used in low-energy houses, but they incur additional investment costs. A more advanced concept than the low-energy house would not be economically feasible if it has to be amortised solely through savings in running costs; however, the Passive House is a simplified concept in which the investment costs for a heating system are substituted by those for the ventilation technology.

Existing house

Low-energy house  

Passive House

Zero-energy house 


280  - 180 kWh/(m²a)

70 - 30 kWh/(m²a)

< 15  kWh/(m²a)
without heating system

 0 kWh/(m²a)
heating demand zero


large, expensive

small but necessary

no longer necessary

seasonal storage?


insufficient due to
large window

exhaust air system with fresh air outlet

supply air/extract air system with highly efficient heat recovery

supply air/extract air system with heat recovery?


cold surfaces;
leaks: draughts

warm surfaces; airtight

very good
very warm surfaces, airtight

surplus and waste heat?
space demand!


 investment costs: high

 investment costs: average
(small heating + exhaust air systems)

 investment costs: average
(no heating, ventilation system with heat recovery instead)

investment cost: very high
additive systems, storage and ventilation





auxiliary energy

Consistent progress from a poorly insulated existing building to a low energy house and beyond that, to a Passive House - investment costs are saved by dispensing with the heating system. Thermal comfort keeps increasing, energy consumption and environmental impact decrease; expenditure for the zero-energy house increases again due to the additive systems.

Research Group for Cost-effective Passive Houses - Phase I
The Research Group was coordinated by the Passive House Institute and sponsored by the following:

Members of the Research Group for Cost-effective Passive Houses were:

Key topics of the Research Group Sessions; the Passive House Information Group
The Research Group members came together for a total of 12 closed sessions. The latest information was exchanged during the lectures and discussions relating to the respective focal points such as thermal insulation, ventilation or ecology. Protocol Volumes were prepared for each session which can be ordered from the Passive House Information Group. See the information regarding the Passive House Information Group on the page about Phase II of the Research Group.

Order Research Group Volume online (in German)


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