LOBSTER is a worldwide unique climate chamber. The thermal satisfaction and behaviour of test persons can be investigated in the rotatable mini office building. © Johannes Lang, BINE Informationsdienst

BINE interview with indoor environment researcher 19.02.2014

Dr Marcel Schweiker in interview with BINE Information Service. He is the project head for the LOBSTER climate chamber, which stands for “Laboratory for Occupant Behaviour, Satisfaction, Thermal Comfort and Environmental Research”.© Johannes Lang, BINE Informationsdienst

The two test persons are working on their own projects. In the test series they are allowed to open or close the windows as they require and also freely use the solar shading. Only the use of the ceiling fan is subject to different requirements each day.© Johannes Lang, BINE Informationsdienst

Satisfaction with office environment put to the testEnergy efficient buildings can achieve high user acceptance in summer even without active cooling. However, with extended periods of hot weather or with high internal thermal loads, these buildings and thus the heat tolerance of the users can increasingly come up against their limits. With LOBSTER, an experimental climate chamber at Karlsruhe Institute of Technology (KIT), the adaptive behaviour of office users and how this impacts on their perceived thermal comfort is being investigated under typical office conditions. BINE Information Service spoke with project head Dr. Marcel Schweiker about the results of the initial test series.

BINE Information Service: Mr Schweiker, you are investigating the satisfaction and performance of people in office buildings. What has this to do with energy efficiency?Schweiker: Actually quite a lot! A large part of the energy is used in office buildings to make it as pleasant as possible for the people working in them – both in winter and in summer. If the users are dissatisfied, they perform less well. They complain to the building operator or they intervene in the building operation. That can be either helpful or contra productive for the indoor environment control and the energy efficiency. This can mean that buildings designed to be very energy efficient require considerably more energy during actual operation. Users sometimes behave completely differently than was expected during the planning.

… because they feel uncomfortable?Yes, or because they do not agree with what the designers or the facility

management have prescribed. Then people in offices begin to think about how they can change the indoor environment to meet their own preferences or can adapt themselves to meet the not ideal situation. Or they are simply dissatisfied.

What do satisfaction and performance depend on in detail?The term satisfaction is multifaceted. People do not primarily think about the thermal indoor environment. In

The term satisfaction is multifaceted. People do not primarily think about the thermal indoor environment. In research we distinguish between thermal perception and thermal satisfaction, whereby the temperature, air speed and air humidity parameters all play a role. But higher or lower temperatures do not always make us dissatisfied. And sometimes a cool breeze provides the necessary cooling. The perception always has something to do with the current situation, activity or expectations. Thermal perception and thermal satisfaction are situation-based and subjective factors.

And why are you interested in the performance?For employers, the performance is probably more important than the thermal satisfaction, but both factors are linked to each other. That is something that we want to investigate in detail during the next few years. The focus is on various factors that probably play a role in this regard. For such work we are using LOBSTER – a new, worldwide unique mini office building as climate chamber.

What exactly are you researching in this experimental office?In our first test series, we invited test subjects to work in the two offices of LOBSTER. The participants were allowed to work on their own projects, to open or close windows as required, and also to use the solar shading as required. Only the use of the ceiling fan was subject to different requirements each day: on the first day they were not allowed to use it. On the second day they were allowed to use it. On the third day they were allowed to use it but it was configured in such a manner that it practically had no cooling effect on the workspace. Unknown to the test persons, in this case the experimental design was configured so that the rooms were heated during the course of the day and therefore became continually warmer – irrespective of whether windows, solar shading or the fan were specifically used. We wanted to find out whether the mere ability to have control increased the satisfaction or whether intervention possibilities must also be effective. The fan on the third day was therefore a kind of placebo.

Placebos do not provide more satisfactionAnd what did you find out with your first test series?We were able to see that a placebo intervention option did not really improve the satisfaction. Activating an effective measure, on the other hand, significantly increases the satisfaction and the heat tolerance, despite having the same temperature. However, I must qualify this by saying that we need to investigate these effects much more precisely, to a greater extent, and with a changed research design. That is something that we want to tackle next summer when we will adopt a more interdisciplinary approach so that we can analyse not just the physiological aspect but also the psychological and behaviour-related issues.

In summer, is it at all possible to attain the necessary satisfaction and performance in buildings without air conditioning?I believe so. Various studies consistently indicate that people in passively cooled buildings where the windows can be opened and provide solar shading are no less satisfied than in air-conditioned buildings. This is because specific possibilities to act and exert an influence improve the satisfaction. When designing such buildings, one of the prime concerns should therefore be – by means of the building concept – to keep the summer heating down to an acceptable level. The building concept certainly requires a certain robustness. In addition, various possibilities should be provided to enable users to specifically influence and control their environment: for example, a ceiling fan in addition to windows and solar shading provides a helpful element with which at least the use of increased air speeds can achieve a cooling effect when there is very warm outside air. This increases the individual options for controlling the indoor environment and increases the temperature range in which people still feel content in offices.

This therefore means that energy efficient buildings should not be fully automated machines because users require individual possibilities for intervention to keep them satisfied?Precisely! For example, fully automated solar shading systems are not accepted at all. The solar shading moves upwards when a gust of wind comes. Then it moves back down again. And that can happen several times within an hour. It is therefore about finding the right balance between the necessary requirements of the building automation system and the individual ability of users to intervene.

And when some users behave counterproductively?In the ideal case, users know that specific individual behaviour could create an unfavourable indoor environment for the following day or even for the rest of the week. Perhaps after a certain period of time they will notice that they can trust the building automation system. It is certainly concerned with the partially different goals of two different parties: on the one hand there is the building automation system, which thinks in terms of achieving a good indoor environment for everyone and a favourable energy balance for the entire building. And on the other hand there are the individual users with their personal and situation-based needs, even if it is only the wish for a view outwards.

An experimental office playgroundAnd how can this dilemma be solved?LOBSTER is intended as an experimental playground in order to better understand people working in offices and their behaviour regarding the indoor environment. We also hope that this will provide us with data for a detailed model development. This could be helpful for more precisely designing buildings and their automation system, since people’s physiological responses to a specific thermal indoor environment are relatively well researched. What is completely lacking, however, is a precise understanding of comfort perception and performance in accordance with both the possibilities for exerting influence and the adaptive behaviour when adjusting to a specific indoor environment.

Do the participants in your experiment behave reasonably?The fan is mostly switched on at precisely the right time. However, we cannot judge whether it would be switched off again in practice because in our experiment it became continually warmer until evening. A modern ceiling fan therefore clearly provides a simple and cost-effective tool for increasing the comfort.However, the solar shading was mostly used too late and, when it was used, this had less to do with thermal reasons and much more to do with preventing glare. With such behaviour, passively cooled buildings would become unnecessarily warm. The participants do not behave with particular foresight and also not energy efficiently. Perhaps that is also partly because they have never really learnt how to deal with solar shading devices.With the window ventilation, the participants should have actually opened the windows in the morning in order to allow cool air into the office. During the rest of the day they should have then kept the windows closed in order to keep the warm outdoor air outside. But some people do the exact opposite: in other words they do not open the window until it is warmer outside than inside. Others, on the other hand, behaved almost impeccably and with foresight.

Simulation becomes more precise – and more demandingHow can a better understanding of users be utilised for simulating buildings?The simulation of buildings is still based on very simple profiles for the user behaviour. That is not exactly very realistic because not all users are the same and they do not always behave reasonably. Here it would be much more advisable to use probabilistic models. We assume, for example, that at a specific room temperature, the windows will be opened with a probability of 30 per cent. That makes the simulation more complex, but it also makes it easier to see which extreme values can occur during the operation of buildings. This therefore makes it possible to design buildings and the building automation system more precisely and realistically.

And can that also help the building operation?It is conceivable that in future the building automation system will store the needs and usage profiles of individual users and organise the indoor environment control system not just on the basis of weather forecasts but also based on specific rooms or individual users. For example, a different cooling strategy would be realised for people who like having the window open than for people who do not like the fan running because they have sensitive eyes. But apart from the data protection issues that still have to be resolved, that is still a long way off in the future.

(jl)