Contents

1. Satisfaction – Indoor environment – Influence of users – Energy concept – Architecture
2. Results of the satisfaction study
3. Conclusions drawn from the study
4. Sources

How satisfied are employees with their workplace? Can this satisfaction be measured? How do people and buildings interact with each other?

There are many reasons why a high degree of satisfaction with one’s workplace is important and is perhaps even a decisive criterion for the quality of a building. Up until now, this subject has not been given much attention in practice, but has been monitored from a scientific viewpoint. Planners, investors and users of building projects are now beginning to focus more strongly on this ‘satisfaction’. The process of building certification which is starting in the real estate sector is also helping to emphasise the importance of socio-cultural factors. When evaluating the overall sustainability of a building, socio-cultural factors must also be taken into account alongside economic and ecological parameters which can be calculated or measured for buildings. The degree of user acceptance of a building can only be measured by statistically analysing subjective statements from the users – particularly when an existing building is to be evaluated while it is in use.

1. Satisfaction – Indoor environment – Influence of users – Energy concept – Architecture

The investigation described here is intended to evaluate the satisfaction of building users in general, as well as quantifying specific satisfaction parameters. As part of this investigation, the users in 10 EnOB (energy-optimised building) model projects (three of which are presented here, see the InfoBox in the top right) and in other buildings were surveyed in detail. The data collected was then analysed against the measured building data and the building’s architecture and energy concept. The study was supported by the German Federal Ministry of Economics and Technology as an EnOB research project.

User satisfaction is defined here as “personal satisfaction with the thermal, visual and acoustic comfort, the indoor air quality, and the office equipment and layout”. To measure and compare satisfaction levels, the individual parameters that determine comfort at the workplace and in the building must be described statistically and related to room conditions and the building environment. Differences in the responses between surveys carried out in summer and winter were also evaluated.

Up to now, a standardised questionnaire has been completed by almost 2,000 employees in various office buildings in Germany. The random survey sample for each building included between 30 and 100 people. The room temperature and humidity in the selected rooms in the buildings in question were measured at the time of the surveys and were included in the evaluation. It was possible using so-called multivariate analysis methods to test and validate the correlations between the various factors which influence perceived comfort. Details of the test conditions and evaluation methods are described in [Gossauer, 2008]. The results of the study are also intended to serve as the basis of a standardised tool for evaluating buildings, which can then be used in the context of facility management.

2. Results of the satisfaction study

Satisfaction parameters are relatively independent of one another

The parameters for thermal, visual and acoustic comfort, indoor air quality, and office layout and equipment influence each other only very weakly in this survey sample. As a generalisation, this means that dissatisfaction with the room temperature does not necessarily result in a negative evaluation of the light or sound situations at the workplace. One exception here is the interdependence of satisfaction levels with the air quality and satisfaction with the room temperature.

Significant interdependencies were found within the individual satisfaction areas. For example, the perceived room temperature is only one of a number of parameters that influence satisfaction with the room temperature. Users are even less satisfied with the indoor environment in summer than in winter, despite the similar average temperatures.

Perception of thermal comfort

A decisive factor in satisfaction with the indoor environment is the amount of influence people feel they have over the room temperature (see Fig. 2). Similar results can be found in other international studies – e.g. [Brager, de Dear 1997] or [Gottschalk 1994]. For example, the effect of opening a window on the room temperature is more perceptible in winter due to the larger difference between the indoor and outdoor temperatures in winter compared to summer. For this reason, people feel they have less personal control over the room temperature in summer.

Additional factors influencing satisfaction with the room temperature include the perceived air quality and the perceived air humidity; these two factors also correlate with each other. Users are more dissatisfied with the air quality and the room temperature if they feel the indoor air is too dry (winter). Poor air quality in summer is often ascribed to the high room temperatures.

Differences relating to the time of year and time of day

Employees who express a neutral opinion regarding thermal comfort are more satisfied with the room temperature in winter than in summer. Even though most buildings had room temperatures within the ISO 7730 comfort range during the survey period in summer, only around 30% of all users surveyed were “satisfied” or “very satisfied” with the temperature at their workplace (see Fig. 3).

Just as satisfaction with temperature, the perception of temperature is also significantly different in some of the buildings. Figs. 4 and 5 show how temperature perceptions in summer and winter vary in relation to the opinions “dissatisfied” and “very dissatisfied”. In the warmer season, almost half of those surveyed were “dissatisfied” or “very dissatisfied” with the room temperature.

When comparing dissatisfaction levels between the categories “a little too cold” and “a little too warm” in Fig. 4, the number of dissatisfied people was higher for those who thought it was “a little too cold” at the time of the survey and looking back on the afternoons than it was for the “a little too warm” category. In winter, there seems to be a slight bias in terms of temperature perception in favour of accepting “a little too warm” as compared to “too cold”. This may be related to expectations regarding the course of the temperature over the day.

In Fig. 5, the first observation is that the level of dissatisfaction for all time periods for the “just right” temperature perception is significantly higher in summer than in winter. 36% were dissatisfied when the survey was carried out, as compared to 10% in winter. This again clearly shows that temperature satisfaction is influenced by other factors alongside temperature perception.

More detailed investigation of the retrospective and current evaluations with the time of day shows that temperatures that are too warm are regarded as unpleasant in the mornings (or when arriving in the morning) in summer, whereas environments that are too cold are deemed undesirable in the afternoons: this evaluation is probably caused by expectations regarding the indoor environment (rising room temperature).

Influence of building services

Buildings can be split into two groups with regard to thermal comfort in summer: buildings without cooling and buildings with cooling. The room temperature was felt to be warmer in the non-cooled buildings and satisfaction with the indoor environment was lower on average – even though the temperatures measured were the same or only differed slightly during the survey periods. This does not fit in with adaptive comfort models which lead one to expect a higher tolerance range for this category of building. This shows again that other factors are dominant when it comes to evaluating thermal comfort. Results of the “discriminant analysis” support the theory that long-term experiences regarding indoor environment play a role in retrospective temperature evaluation and especially in satisfaction with temperature. For example, this means that a few specific days which were very hot and unpleasant in the office will probably remain prominent in the employees’ memories.

On the whole, it became clear that those buildings with a hybrid concept which still allows the user to influence the indoor environment were given the most positive ratings out of all the buildings evaluated. This includes buildings with thermal building element activation and a controllable ventilation system.

Dress code is a disadvantage

Another interesting effect can be observed from the survey data: satisfaction with room temperature is significantly higher in buildings where there is no dress code or where this code is relaxed in the summer.

Overall result...

Statistical analysis has shown that the “overall satisfaction with the workplace” is mainly based on the following six satisfaction parameters (in order of decreasing relevance):

• “Satisfaction with the office layout and equipment”
• “Satisfaction with the air quality”
• “Satisfaction with job tasks”
• “Satisfaction with the room temperature”
• “Satisfaction with the sound level”
• “Satisfaction with the situation regarding natural daylight”

The weighting attached to the individual satisfaction parameters for overall satisfaction with the workplace differs from building to building. For example, thermal comfort may have a much larger influence on the overall workplace satisfaction than satisfaction with the light situation at the workplace does. The consequence of this is that an overall satisfaction index can only be formulated specifically for each given building, taking the weighting factors valid for that building into account.

The different weightings attached to individual parameters regarding overall satisfaction can be well represented graphically using a so-called importance-performance matrix, which until now has mainly been used in market research (see Fig. 6). A value for the estimated importance of each parameter in general satisfaction (0 = not important at all, 1 = very important) is obtained from the correlation of individual satisfaction parameters with general workplace satisfaction.

The potential for optimising a given building can then be determined by comparing the individual satisfaction parameters in terms of their importance for overall workplace satisfaction with the relevant average values for the individual parameters. It is then possible to identify at a single glance the weaknesses in the building (operation) from the user’s point of view and the urgency with which something must be changed (see Fig. 6). This relates not only to the operation of technical equipment, but also includes the match between user behaviour and the relevant building concept.

Analysis of the overall survey sample shows that, on the whole, the parameters air quality and room temperature were weighted the highest by the users (followed by office equipment) in the 17 buildings investigated. According to this method, the light situation at the workplace has the lowest influence on the overall rating (see Fig. 7). This result agrees well with the European study reported in [Humphreys 2005].

3. Conclusions drawn from the study

The main conclusion to be drawn from the study is that it is possible to identify optimisation potential in building operation in an empirically reliable and systematic manner with the help of user surveys. Weaknesses of a particular building from the user’s point of view can be identified using an importance-performance matrix which contains the individual satisfaction parameters with their importance (as estimated from correlations) for general satisfaction. This information provides support to the building manager in optimising operations. The surveys help to involve users in the building optimisation process. In addition, project planners and managers can obtain feedback for future building projects, thus contributing to more requirement-focussed project planning – something that is definitely needed.

Positive results achieved in good buildings

Ratings for many aspects of workplace environment have been very positive in the buildings studied so far. Overall, this reflects the high standard of the buildings investigated. For this reason, the dividing lines between “satisfied” and “dissatisfied” or between “important” and “unimportant” in the identification of optimisation potential can only be definitively determined as part of a further comparison with “more average” buildings. In this context, it would be possible to identify whether a lower building standard has a significant effect on the individual satisfaction levels and their weighting for overall satisfaction.

Dissatisfaction in summer

The results show a significant difference between satisfaction levels with room temperature in winter and summer: satisfaction was considerably lower in summer despite neutral temperature perception and the similar room temperatures measured. It became clear that other factors, such as the perceived effectiveness of measures to modify the indoor environment, play an important role alongside temperature perception itself. One such factor is expectations – for example, concerning the change in the room temperature over the course of the day.

To reliably evaluate thermal comfort, it would appear to be essential to carry out separate surveys in summer and winter so as to take into account the different interrelationships between the variables and their influence on satisfaction with the indoor environment. The seasonal differences are less pronounced in other areas, such as the evaluation of noise at the workplace or of office layout and equipment. As regards visual comfort, the question of a more suitable investigation method to take into account the daylight dynamics over the course of the day and year arises.

Factors contributing to high satisfaction

With the help of user surveys, concrete measures can be identified for new building projects that will make a significant contribution to increased workplace satisfaction:

• Natural ventilation of the office rooms
• Individual temperature control (in summer and winter)
• Differing layout for all work areas
• Small units in the office (single office rooms)
• No large hall-like office spaces

Small offices are better

In particular, the satisfaction with the office equipment and layout and the acoustic comfort is generally the highest in single offices. A maximum of four occupants was deemed to be the optimal office size in personal interviews. The ability to influence other parameters – such as ventilation, room temperature, shading and artificial light – is the greatest in small units, and, as has been shown, this increases satisfaction with the workplace.

Cooling is desirable

The results obtained demonstrate that users would like to have cooling or be able to influence the workplace temperature in summer when temperatures are high. One issue that future building concepts will have to consider is how to give users these possibilities while at the same time saving on energy.

This study was supported by funds from the German Federal Ministry of Economics and Technology, and the authors would like to express their thanks for this support.

Authors: Elke Gossauer, Karin Schakib-Ekbatan, Andreas Wagner
Editor: Johannes Lang

4. Sources

[Gossauer 2008] Gossauer, E (2008), ‘Nutzerzufriedenheit in Bürogebäuden’, Dissertation, Fraunhofer IRB Verlag, vgl. auch die auf dieser Website verfügbare PDF-Version unter 'Publikationen'.

[Brager, de Dear 1997] Brager, G.S., de Dear, R. (1997) ‘Developing an Adaptive Model of Thermal Comfort and Preference’, Final Report, ASHRAE RP-884, Berkeley, USA

[Gottschalk 1994] Gottschalk, O. (1994) ‚Verwaltungsbauten: Flexibel, Kommunikativ, Nutzerorientiert’, Bauverlag

[Humphreys 2005] Humphreys, M.A. (2005) ‚Quantifying occupant comfort: are combined indices of the indoor environment practicable?’, Building research & information, vol. 33(4), pp. 317-325