Foto: ChristophorusHaus

Technical status of ventilation systems for buildings

Evaluation of existing ventilation systems in Austria considering technical quality and practicability.

Content Description




Starting point of the project: A sustainable and high indoor air quality for living space can generally only be guaranteed with the aid of mechanic ventilation systems. In addition the use of heat recovery installations to reduce the loss of air infiltration heat is essential for low energy houses and/or passive energy houses in order to reach the intended benchmarks.

Ventilation systems with heat recovery installations for living space have not yet become a standard for domestic building which results in insecurity and skepticism as to the technical quality of the systems. This in turn has negative effects on the decision making processes of potential customers and the distribution of ventilations systems.

Objectives: This project focuses on the objective description of the quality of ventilation systems installed in Austria. The most important objective with regard to the objectives of the "House of the Future" program consists of showing positive solutions, mistakes and defects in order to improve the quality of future ventilation systems for living space.

Procedure: The quality of the systems was determined with the aid of a survey of 92 ventilation systems for living space all over Austria. The survey mainly focused on supply and exhaust air systems combined with heat recovery installations. However, also some systems with heat pumps and mere exhaust air systems were analyzed. A catalogue of quality criteria was established in order to guarantee objective evaluation and was used to evaluate the quality of the systems. The evaluation was the result of interviews with users, measurement of data (air mass, pressure loss, noise level ...) and the examination of single components of the system.

General explanation and/or dimensioning of air mass: In order to guarantee a comprehensive understanding of the complex issue also among readers who have not yet been working intensively in this field, one chapter summarizes the most important aspects of ventilation and ventilation systems for living space and explains important components of ventilation systems for living space (e.g. ground heat exchanger) and technical terms (e.g. regulation of constant air mass). This chapter also deals with the most important aspects in determining air mass for ventilation systems for living space.

Quality criteria: One of the essential tasks in order to guarantee the objective evaluation of the systems and the future quality enhancement of ventilation systems for living space was the establishment of a comprehensive catalogue for quality criteria which was continuously improved by integrating the experience of the evaluation processes. Finally 55 quality criteria were established and their relevance and importance were explained. They can be used as a guideline for the dimensioning and/or implementation of future systems.

Analysis of the evaluation: The evaluation was a threefold process: the analysis of the users' subjective perceptions of the system, the quantitative analysis of how many of the systems examined comply and/or do not comply with the criteria and a qualitative analysis in which good solutions and/or selected mistakes and defects are pointed out.

Results and a rough outline: The analysis of the questionnaires and interviews revealed that the owners of the systems rate about 80% of the systems examined as "very good" or "good", i.e. the rate of satisfaction among the users of ventilation systems for living space is very high. Users primarily complain about the noise level. In conclusion of the technical evaluation it must be emphasized that the ventilation equipment as such hardly ever gives reason for criticism. Problems are mostly caused by the general design, insufficient components and controlling strategies.

Most common problems in the design of systems:

  1. unevaluated prerequisites of the building (air density)
  2. noise problems due to insufficient dimensioning of the cross sections of the pipes and valves and/or missing or insufficient sound absorbers
  3. insufficient routing of air flow in the living space
  4. air mass too low (and/or was reduced due to the noise level being too high) and insufficient calibration
  5. ventilation system influences fireplaces in the living space
  6. extractor hood leading to exterior influences ventilation systems
  7. cross sections of openings for air to flow through are often paid too little attention to

The most common mistakes occurring in single parts of the system:

  1. insufficient air inlet with a loss of pressure being too high
  2. missing condensate drain for the ground heat exchanger and/or ventilation device
  3. no humidity resistant insulation of cold pipes (fresh air and exhaust air) and/or no insulation of warm pipes (supply air and exhaust air) in the cellar
  4. filter quality too low and bad maintenance of the filters
  5. systems without regulation of constant air mass are hardly ever balanced (but also systems with regulation have problems in this field)
  6. no notification when a change of filters is needed in the living space
  7. missing or insufficient sound absorbers (between devices or between different rooms)
  8. insufficient cross section of pipes (air flow too fast)
  9. inappropriate material of pipes (flexible tubes)
  10. wrong valves or valves too small (e.g. mere exhaust air valves for supply air)

Further problem areas are the measurement and control parameters which are not used properly or partly calibrated wrongly. Sometimes it is not clear which (single) parameter has to be calibrated in which way.

  • temperature of the bypass for the ground heat exchanger?
  • temperature of the bypass for the heat exchanger in the ventilation system?
  • which ventilation intensity at which time of the day?

Conclusion: Ventilation systems for living space should become a matter of course in the construction of new buildings and the restoration of buildings. The single components necessary for high quality ventilation systems are available. Due to the relatively new topic the designers and implementers of these systems mainly lack training and experience in this field. The authors of this paper hope to have contributed to the implementation of more and better ventilation systems for living space and would be pleased to share experiences and answer any queries.

Project Partners

Project manager

DI Andreas Greml, FHS-KufsteinTirol

Project team

  • DI Ernst Blümel, AEE INTEC
  • Ing. Wolfgang Leitzinger, arsenal research
  • DI Roland Kapferer, ENERGIE TIROL


  • AEE INTEC (Institut für Nachhaltige Technologien)
    AEE GmbH , Technisches Büro für Energie- und Umwelttechnik
  • Österreichisches Forschungs- und Prüfzentrum Arsenal Ges.m.b.H.


Dipl.-Ing. Andreas Greml
Andreas Hofer Str. 7
A-6330 Kufstein
Tel.: +43 5372 71819 - 125
Fax: +43 5372 71819 - 104

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