Comfort for sustainability

Research project on comfort and on the health and recreational value of passive houses

Content Description




Part A: Motivation, Matter, Aims, Methods

The passive house specification is well known as an energy-efficient building standard. Less known is that the passive house concept was derived consistently from comfort and hygiene criteria. However, succeeding in the market comfort might be the point of stress.

Usually, passive houses are not presented as ‘comfort houses' but as ‘houses without heating'. Potential customers of passive houses tend to be afraid of living in a house, which only can be heated through the ventilation system. They ask for a perceptible heating source, e.g. a wall heating or a small heating stove. Some inhabitants of passive houses also express such desires: they don't feel cold in passive houses, but they wish to satisfy needs of warmness, comfort and security.

Comfort ventilation systems are integrative components of each passive house. These systems ensure sufficiently exchange of air in passive houses and therefore guarantee best indoor air quality. The comparison of measurement results of indoor air quality in sleeping rooms reached with and without comfort ventilation systems is an important reason for clients to opt for controlled ventilation and consequently for passive houses.

Besides the arguments of running costs and ecology, which do argue for the passive house concept, comfort arguments need to be strengthened to fix the marketing success of the passive house building standard.

This study made an empirical attempt to prove or disprove comfort problems in passive houses. Whatever the results, they will be a stimulus to further development of key components for passive houses and they will be a useful point on marketing, too.

This study treated two questions on comfort, health and recreational value of passive houses:

  • Question 1: Do occupants of passive houses perceive differences in comfort, if the house is heated a) only by the ventilation system or b) additionally by another heating system (wall heating, ceiling heating etc.)? Is it possible to establish consciously or even unconsciously perceived differences by physiological measurement and/or by psychological questionnaire?
  • Question 2: Mechanical ventilation systems offer good indoor air quality with low concentrations of dust and carbon dioxide. Does better indoor air quality affect nocturnal recreation of passive house occupants? Is it possible to prove effects by comparing sleep quality a.) in rooms with mechanical ventilation and b.) in rooms without mechanical ventilation and closed windows?

The aim of the project was to optimize the requirements of components of passive houses such as heating concepts, heating components, control components, and mechanical ventilation system by introducing the results of measurements of comfort as well as experiences and results from interviews of inhabitants of such buildings.

Furthermore, the advantage in better nocturnal recreation was to be proven by investigating the quality of sleep: Results of comparison of sleep quality with and without controlled ventilation system should underline the importance of a comfort ventilation system for the air and recovery quality. Identification of factors for the well-beings in passive houses and development of a model for the description of the concept ‘comfort', which can be used for the development of marketing strategies. The significance of the construct ‘comfort' with respect to the final purchase decision of the consumer was to be displayed.

Physiological effects were pursued by measurement and analysis of the heart rate variability (HRV) using a miniaturized electrocardiogram instrument (‘Heartman').

In a comfortable thermal surrounding, thermal body regulation is done only by the blood circuit. Therefore, the best chance to measure comfort physiologically is to determine the condition of the blood circuit and the autonomy nervous system.

Psychological investigations have been done by evaluating questionnaires and by analyzing the ‘Focus Group Interviews'. The aim of the interviews with the inhabitants of passive houses was to extract the experiences of the achieved comfort in the building and to comprehend the ‘construct comfort'. The primary aim of the investigation was to deduce marketing-relevant aspects.

Part B: Results and Conclusion

The physiological investigations showed no significant change in the autonomous thermal regulation of the tested persons due to different heating configurations in the buildings.

Pure heated supplied air as well as surface heating systems (wall heating) and also pellet stove heating led to a climatic situation which was equally sensed objectively, via physiological measurements, and subjectively by questionnaires.

The conclusion of the investigations is not statistical proven since the amount of studies is too small. However, it is an indicator for physiological effects of thermal comfort. The physiological measurements validate the method to be appropriate and solid for these kind of investigations of comfort. The result is only applicable for the passive house due to the relative high surface temperature achieved maximum heat insulation. Independent of the choice which heating system is applied, the individual preferred room temperature must be achievable, even if this temperature is 25° centigrade.

The ventilation heating system shows the disadvantage of connected airflow and heating output, which can lead to dry air - most notably in winter, when heating power has to be applied, even if there are no persons present. To achieve room-separate temperature settings additional effort has to be taken into consideration.

For the planning, it is a must to satisfy the desires and requests of the customer. If the planning and the calculation indicate that the individual temperatures can be achieved by direct air heating only but the customer still wishes an additional heating system, the desire of the customer should be fulfilled.

For the time being, it was not possible to achieve deductions for sleep quality with respect to air quality from sleep measurements, due to insufficient CO2 concentrations in the sleeping rooms. However, isolated cases with traceable differences in CO2 concentrations showed also different recovery potential. Though, the performed ECG structure analysis is not capable of a more in-depth analysis of sleep quality and the recovery potential of sleep with regard to air systems.

The psychological surveys, done by questionnaires, yield the result that sleep quality and recovery during sleep is subjectively better when appropriate air ventilation is applied. Therefore, it is recommended to perform further investigations. It would be an option to examine the different sleep phases by the use of a mobile sleep laboratory. The correlation between sleep quality and air-conditioning as well as indoor pollution could be evaluated. Pilot surveys have already been started where EEG (Electroencephalogram) measurements deliver additional results to the analysis with the HeartMan.

An essential point of the study was to gather the consequences of different heating systems on the comfort of passive house habitants. The Focus Group Interviews gave the information how and when the owner uses the heating system. All the participants agreed on the fact that it would not be possible to heat the passive houses only by the air heating system. Nobody wanted to abstain from having an extra heating system to satisfy the individual demands for thermal conditions in case of extreme cold winter. Such safety considerations and the fear of an later debit made the extra heating system crucial. One conclusion is that from the habitants' point of view, the kind of heating system has direct consequences on the well-being and the comfort of the building. The participants have chosen their heating system according to the influence of the system on the ambience of the room. This is valid for wall heating systems as well as for the pellet stove. The wall heating system satisfies the habitants particularly for the emitting radiation from all directions whereas the pellet stove satisfies with visual flames, implicating comfortable ambience.

Consistently and for all habitants, the comfort ventilation system is the most important feature and the most important sales argument. The ventilation system is considerably responsible for the general working of the passive house and bears the sources for comfort, habitation quality and wellness.

Project Partners

Project manager: Gabriele Rohregger
Austrian Institute for Healthy and Ecological Building (IBO)
  • Prof. Maximilian Moser
    Institute of Non-Invasive Diagnosis
  • Johannes Gadner
    IWO - Institut für Wissensorganisation e.V.
  • Renate Buber
    Vienna University of Economics and Business Administration, Department of Retailing and Marketing


Gabriele Rohregger
Austrian Institute for Healthy and Ecological Building (IBO)
Alserbachstrasse 5/8
A 1090 Wien
Tel.: +43 1 319 20 05-26
Fax: +43 1 319 20 05-50