Better climate control through better interfaces

Key words: User interface, indoor climate control, personal control, system feedback, office comfort, user in the loop, Brains4Buildings project

·       The article highlights the importance of well-designed user interfaces for building climate systems.

·       Readers learn that an effective interface can reduce indoor climate complaints by clearly communicating system status and use cases.

·       The article discusses common misunderstandings about interfaces and emphasizes that user satisfaction is increased by providing control and feedback.

We strive to create comfortable indoor environments in buildings, balancing energy efficiency and productivity. However, despite our efforts in designing advanced climate systems, office users still report discomfort. One key aspect that is often neglected is the user interface. An effective user interface can greatly minimize complaints.

How can users take their role?

It is known that there are regular complaints about the climate in offices. It is understandable that a system-controlled indoor climate is not always perceived as comfortable by everyone. After all, office users differ in metabolism, physiology and clothing, to name just a few aspects.

Therefore, adaptable controls in the workplace are essential. Studies show that personal control is an influential factor in office user satisfaction, comfort and productivity [1]. It is crucial for users to adjust the indoor climate to their needs through interfaces like thermostats or displays.

Misunderstandings about interfaces

There are common misconceptions about the use of interfaces in controlling indoor climates. One misconception is that users are satisfied if they don't adjust the settings, but research shows that users often don't adjust settings because they either don't understand how to use the interface or doubt its effectiveness [2]. Another misconception is that the interface doesn't need to work as long as users believe it does, but this can lead to dissatisfaction and a lack of trust if users realize the interface is ineffective.

In our own study on the interaction between users and climate interfaces [3], we saw exactly this phenomenon, even though the interface in question did actually work: Office workers felt cold in winter, and had the feeling that the thermostat, depicted in Figure 1, didn’t work. They checked their thermostat by setting it to 30°C, expecting it to get very hot. When it didn't, they concluded the thermostat was broken and felt the climate was uncontrollable. However, the thermostat did work but only allowed a 2°C adjustment, which the users didn't know and couldn’t derive from the interface. This misunderstanding led to dissatisfaction and distrust in the system, even though the interface was functional and the system worked.

Figure 1. This interface implies that temperatures between 5°C and 30°C can be set. However, in the office where this interface was photographed, the temperature can only be varied by −2°C to +2°C, leading to distrust in the interface and the climate system.

Good interface design

So, what makes a good interface? To find out, we interviewed a total of 37 office workers from five different office buildings. The results of this study [3] can be summarized in 6 themes that are important when developing or choosing an interface. These six themes provide guidance on what an interface should be able to do (see Figure 2):

1.    Communication of complex information.

2.    Communication of the status of the system

3.    Communication of what users can do

4.    Support in considering the consequences of choices (the “why”)

5.    Communication about the degree and possibility of control

6.    Ensuring alignment of interface design with system functionality

Figure 2. Six themes important in interface development or interface selection: what should an interface be able to do?

1. Communication of complex information

It starts with the way information is communicated. Users don't have the same knowledge as facility managers, so keep interfaces simple but not overly simplistic. Too much information can overwhelm users, while too little can confuse them. Show only what is necessary and what users can interact with. For example, omit relative humidity if users can't influence it. Always test your design with potential users to ensure it helps them achieve their goals.

2. Communication of the status of the system

The interface in Figure 1 lacks essential information about the system's status, such as the current temperature, the desired temperature, and whether the system is working to achieve it. It only shows the temperature set by the user. When employees set the thermostat to 30°C, they received no feedback that the system actually started heating, so they didn't notice the small increase in temperature and thought the thermostat was broken. Home thermostats often show a flame to indicate heating, which is a simple way to communicate the system's status.

3. Communication of what users can do

For users to take control at their workstations, they need to understand what they can and cannot control. This starts with finding and recognizing the interface. In practice, this is not always common. For example, in my office, a new building completed in 2022, the temperature and lighting are controlled via a QR code on a wall outside the workspaces and meeting rooms. Many users don't adjust settings because they don't know about the QR code or where to find it.

The interface in Figure 1 appears clear about adjusting the temperature, but it actually says, 'you can adjust the temperature from 5°C to 30°C.' So, in fact, this does not effectively communicate what the user can and cannot do."

4. Support in considering the consequences of choices (the “why”)

Controlling indoor climate is complex, as user actions like opening a window can improve air quality but also increase energy consumption. Automatic controls might consider these factors, but when a user takes over, this information is relevant for this user too.  Our research [3] shows that users appreciate help with this. An interface that gives such guidance is the TU Delft's window feedback system [4], which uses a light strip to guide users on window operation as effectively as possible. Similarly, TNO's CoolDownCoach helps residents keep their homes cool by advising on window and blind operation (see Figure 3).

Figure 3. CoolDownCoach: example of an interface that supports occupants in weighing the consequences of choices. In this case, opening windows and operating blinds.

5. Communication about the degree and possibility of control

While much has been written about the pros and cons of automatic controls and what degree of control is preferable [e.g. 5, 6], one thing is clear: users must be able to override automatic settings. Understanding the current actions of the climate system is crucial, especially with building flexibility. For example, if a building heats in advance when electricity is cheap and turns down the heat when electricity is scares, users need to know and understand this. Real-time communication through interfaces or displays will greatly aid in the acceptance of such systems.

6. Ensuring alignment of interface design with system functionality

A major reason the interface in Figure 1 generates complaints is that it implies users can raise the temperature to 30°C, while in fact only +2°C is possible. This mismatch leads to dissatisfaction and distrust in the system, as is explained above. The lesson from this example is that interfaces must match the systems operation; there's no one-size-fits-all solution.

Conclusion

The importance of well-designed user interfaces for building climate systems cannot be stressed often enough. Effective interfaces can not only reduce indoor climate complaints but also contribute to the comfort, satisfaction and productivity of office users. By clearly communicating system status and usage options, and giving users the control they need, we can make significant improvements in how people experience their work environment.

The 6 themes we identified - communication of complex information, system status, usability, consequences of choices, degree of control, and connection to system functionality - provide a solid foundation for designing interfaces that really work for users.

Acknowledgements

The research behind this article was conducted within the Brains4Buildings project with funding from the Scheme: Mission-Driven Research, Development and Innovation (MOOI). [7] This article has previously been published in a more extensive version in TVVL magazine (2025, nr2, in Dutch).

References

[1]     Kwon, M., Remoy, H., van den Dobbelsteen, A. & Knaak, U. (2019) Personal control and environmental user satisfaction in office buildings: Result of case studies in the Netherlands. Building and Environment, 149, p 428-435. https://doi.org/10.1016/j.buildenv.2018.12.021.

[2]     Karjalainen, S., & Koistinen, O. (2007) User problems with individual temperature control in offices. Building and Environment, 42, p.2880–2887. https://doi.org/10.1016/j.buildenv.2006.10.031.

[3]     Spiekman, M., te Duits, N., Lange, V., Jeurens, J. & Sluis-Thiescheffer, W. (2023). Methodology to develop interfaces to help office users better understand control strategies of climate systems. 18th Healthy Buildings Europe Conference, June 2023, Aachen, Germany.

[4]     Yüksel, S. (2023). 'Human-Window Interaction in open-plan workplaces: Guiding occupants to efficient window operation through window feedback systems', Master Thesis, Delft University of Technology.

[5]     Karjalainen, S. (2013). Should it be automatic or manual—The occupant’s perspective on the design of domestic control systems. Energy and Buildings, 65 p.1-15. https://doi.org/10.1016/j.enbuild.2013.05.043.

[6]     Ahmadi-Karvigha, S., Ghahramani, A., Becerik-Gerber, B. & Soibelman, L. (2017) One size does not fit all: Understanding user preferences for building automation systems. Energy and Buildings, 145, p. 163-173. https://doi.org/10.1016/j.enbuild.2017.04.015.

[7]     https://brains4buildings.org/.