# COOLIBRI project. Lowering cooling energy use by coupling ceiling fans to air conditioners: an adaptive user perspective

Maäréva Payet, Maxime Boulinguez, Valentin Fargeas

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Maäréva Payet, Maxime Boulinguez, Valentin Fargeas. COOLIBRI project. Lowering cooling energy use by coupling ceiling fans to air conditioners: an adaptive user perspective. Journal of Physics: Conference Series, 2025, 3140 (11), pp.112005. 10.1088/1742-6596/3140/11/112005. [hal-05477410](https://hal.science/hal-05477410v1)

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# COOLIBRI project. Lowering cooling energy use by coupling ceiling fans to air conditioners: an adaptive user perspective

M Payet¹², V Fargeas², M Boulinguez¹

¹ Laboratory PIMENT (Physics and Mathematical Engineering for Building, Energy and Environment), University of La Réunion, Campus universitaire de Terre Sainte, 97410 Saint Pierre, La Réunion

² LEU Reunion (Urban Ecology Laboratory), 97410 Saint Pierre, La Réunion, France

mp@leureunion.fr

**Abstract.** In tropical regions and French overseas territories, air conditioning (AC) accounts for over 40% of the energy bill in non-residential buildings. As climate change intensifies and cooling demand increases, finding energy-efficient alternatives to conventional air conditioning systems is crucial. Hybrid solutions that combine AC with ceiling fans (CF) are gaining interest as a means to reduce energy consumption while maintaining thermal comfort. However, their effectiveness depends on user behaviour and system integration, making this an important area of research. The COOLIBRI project investigates an integrated control approach that links AC operation with CF activation to optimise energy efficiency. A survey was conducted among 125 office building users in Réunion, Guadeloupe, French Guiana, and New Caledonia—territories with distinct climatic conditions—to assess their current cooling practices, perceptions, and expectations. The study collected data on building characteristics, cooling equipment, and users' daily habits regarding AC and CF usage. A mixed-method approach combining quantitative and qualitative analysis was used to identify general trends and specific barriers to adopting hybrid cooling solutions. A key finding from the study is that, following a preliminary survey, users in our sample are open to adjust their habits and raising the air conditioning setpoint above 26°C when using a ceiling fan, even without having conducted any experimentation. However, it was also observed that this willingness to change habits tends to decrease with age. This is encouraging and demonstrates real potential for promoting this solution. The findings also underscore the need for enhanced education and awareness among users.

## 1. Introduction

Urban areas account for 40% of total energy consumption, primarily driven by commercial and residential buildings. Since 2007, more than half of the global population has been urban, resulting in increased demand for energy-efficient solutions in these environments [1].

Combining ceiling fans with air conditioning is a promising strategy for reducing energy consumption in air-conditioned buildings, accounting for over 40% of the energy bill in non-residential buildings in tropical climates. The two separate solutions are already well integrated, particularly in tropical climates, with numerous existing design and implementation guides, but their combination is not yet established [2][7]. Atthajariyakul et al. [3] demonstrated in laboratory experiments in Thailand that the temperature setpoint of air conditioning can be increased to 28°C when a desk fan providing air
velocities between 0.5-2 m/s is used, resulting in significant energy savings. This finding suggests that ceiling fans can enable higher AC setpoints without compromising comfort.

Further research supports the potential of ceiling fans to enhance the efficiency of air conditioning systems. Chen et al. proposed a system that replaces traditional supply ducts with air nozzles feeding fresh air directly to the fan blade, improving air mixing and allowing for a warmer operating temperature of 28°C for air conditioning units [4]. This system yields a more uniform temperature distribution, eliminating cold spots commonly associated with traditional air conditioning systems.

The combined use of ceiling fans and air conditioning can also downsize cooling equipment, such as chillers, pumps, and cooling towers. By increasing the temperature setpoint, the maximum load on these systems is reduced, resulting in lower initial investment and operating costs. Malik et al. [5] simulated energy demand under a "Fan-First" scenario and found reductions of up to 76% in energy consumption and greenhouse gas emissions, while also improving comfort levels. Fans can push the comfort threshold further, providing a more energy-efficient alternative to relying solely on air conditioning.

Additionally, Miller et al. [6] conducted a 29-month survey in a building retrofitted with 99 automated ceiling fans, finding a 36-41% reduction in air conditioning compressor use. This reduction in compressor use allowed for a wider range of comfortable temperatures, further demonstrating the energy-saving potential of integrating ceiling fans with air conditioning systems.

A recent study on the tropical climate of Singapore [8] showed that 32% energy savings can be expected by raising the set point from 24 to 26.5°C in offices. The use of ceiling fans helps maintain and even improve comfort, eliminating overcooling and drafts (i.e., the feeling of being too cold in some air-conditioned areas).

While recent research highlights the benefits of jointly utilising a ceiling fan with air-conditioning, there are few mentions of user acceptability and understanding of this coupled solution. If space cooling is not fully automated, it is necessary to understand how to make the concept acceptable by user for best efficiency.

## 2. Research methodology

### 2.1. *The COOLIBRI project*

This study is part of the Coolibri project. It aims at studying both technological feasibility and users acceptance of coupling ceiling fans and air conditioning. A focus is made on energy management and user behavior change management in the context of french tropical overseas territories. How can these solutions be combined? Should the use of AC be conditional on the use of ceiling fans? How can the lack of understanding of the concept and potential non-acceptability be an obstacle to full deployment? Are there three questions the project aims to contribute to.

The COOLIBRI project is divided into 4 distinct tasks. Task 1 consists of reviewing technological coupling solutions and the associated control systems, and carrying out a preliminary survey to catch users' habits / obstacles / understanding in buildings using ceiling fans and air conditioning at the same time. Task two is to test and quantify, through experimentation on occupied buildings, the feasibility, the energy performance and user acceptance levels of coupling solutions. Task 3 aims to develop a technical guide that presents all the results and incorporates operational technical specifications for relevant coupling solutions. The final task is to promote and disseminate the results.

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Overview of the COOLIBRI project tasks</figcaption></figure>

This paper presents the results of the preliminary survey conducted in Task 1 lead by LEU Reunion
COOLIBRI is funded by ADEME, the OMBREE program and EDF. We project team consist in an automation specialist QWNRJ and two building engineering firms in Réunion (LEU) and Guadeloupe (EQUINOXE).

## 2.2. Presentation of the survey

We conducted an online survey targeting users of buildings equipped with both air conditioning and ceiling fans to better understand their behaviour regarding the combined use of these systems, their approach to achieve hygrothermal comfort in this context, and their overall feedback. The survey covered all French overseas territories. To collect responses, the survey was distributed through various communication channels used by the project's stakeholders, including social media and email campaigns.

### 2.2.1. Goals
Beyond obtaining user feedback, the survey aimed to identify trends and user profiles. It also sought to assess the extent to which users would be willing to adopt a more eco-friendly approach to hygrothermal comfort management while maintaining the same level of comfort. Additionally, it aimed to identify potential barriers to the widespread adoption of a coupling solution, particularly in terms of awareness. For example, users' understanding of the energy consumption differences between a ceiling fan and an air conditioning system.

### 2.2.2. Organisation
To achieve these objectives, the survey included both qualitative and quantitative sections. The quantitative questions helped categorise answers based on factors such as gender, age, geographic location, type of cooling system used (natural ventilation, ceiling fans, air conditioning), control over system usage, air conditioning usage periods, and general habits. The qualitative questions were more open-ended, allowing participants to share subjective insights on comfort management, hygrothermal conditions in shared spaces, and their willingness to adopt more energy-conscious behaviours.

# 3. Results

We obtained a total of 125 responses from all the territories (La Reunion, French Guiana, Guadeloupe, New Caledonia). However, for the purposes of this paper, we are only dealing with the 107 responses from users located in La Reunion, i.e. 84% of the sample.

## 3.1. Who are the users ?

43% of users are women and 56% are men, 1% preferred not to reply. They are aged between 20 and more than 60 years old (20-29 years old : 15%; 30-39 years old : 33% of the sample ; 40-49 years old : 29% of the sample ; 50-59 years old : 19% of the sample and 60 years old and more : 4% of the sample).

## 3.2. Where do they work ?

73% of respondents work in shared or open spaces. This led us to question how thermal comfort is managed in shared spaces. When ceiling fans are individually controlled, each person adjusts their own fan. However, when ceiling fan and air-conditioning controls are centralised, decisions are made by majority rule, compromise, or simply by the first person to feel discomfort. As a result, thermal comfort is often managed through discussion among space's occupants. However, a clear trend emerges: the larger the space (and its associated cooling systems), the more challenging it becomes to balance individual preferences and achieve a satisfactory level of comfort.

## 3.3. Ceiling fans are well-integrated

Ceiling fans are widely used, with 96% of users using them at least during the hot and humid season (i.e Mean temperature between 22.8 °C and 28°C / relative humidity between 69.6 % and 79% ; on the three first zones described by the Regional Standard for Energy Efficient Building PERENE 2009 [9]).
However, some noted that they do not use ceiling fans because air conditioning is sufficient on its own.

The results also indicate that highest ceiling fan speeds are rarely used. 75% of users feel discomfort with high speeds. The most common complaints included:

* Ceiling fan noise

* Blowing papers or other lightweight objects

* Dry eyes

In tropical climates, based on our experience, users generally retain direct control over ceiling fan operation and frequently adjust fan speed settings themselves.

### 3.4. *Uncontrolled air-conditioning use is too prevalent.*

Despite the widespread use of fans, 16% of users reported occasionally using air conditioning in winter, and 27% reported using it during the mid-season. 79% of them set their air conditioning temperature setpoint above 24°C, suggesting a relatively moderate and mindful use of cooling. However, the proportion of users setting temperatures below 24°C remains significant, highlighting the need for further awareness efforts.

A correlation was found between age and set temperature, indicating that older individuals tend to set lower temperatures. This trend may reflect a lower awareness of energy efficiency among younger generations or be linked to physiological and metabolic changes that slow down with age.

<figure><img src="image_3.png" /><figcaption>**Figure 2.** Distribution of the usual temperature setpoint</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Figure 3.** Temperature setpoint by user age</figcaption></figure>

#### 3.4.1. Coupling ceiling fans to air conditioners has become increasingly popular but remains misunderstood.
77% of users reported that they sometimes use ceiling fans and air conditioning simultaneously. However, 74% of them do not increase the temperature set point when using both together. This suggests that, rather than leveraging the fan to reduce air conditioning use, they see it as an additional cooling source. Additionally, user comments confirm this behaviour, indicating that people tend to adjust the air conditioning first before considering the ceiling fan. This pattern is primarily influenced by a lack of awareness of how fans impact perceived temperature at a very low energy cost (20 times less than AC). This could explain why the combination remains underutilised as an energy-saving strategy.

The most significant drawback of not adopting joint utilisation is the variation in thermal perception between individuals. Additionally, factors such as their position within the environment play a role. As an example, sitting near a properly shaded window for benefiting from natural ventilation or sitting just under a ceiling fan brings a totally different feeling than standing close to a sunny window. These differences in comfort levels made it difficult to establish a uniform approach to using both systems together.

The positioning of ceiling fans and air conditioners also has a significant impact on comfort. Lack of awareness of both systems energy use also lead to a misunderstanding of the benefit of the concept.
Occupants avoid using both system together, thinking that each system separately consumes less energy than when combined. Eye dryness provoked by air movement is another drawback mentioned by surveyed users

3.4.2. *Change of practices* After explaining and raising the awareness of the users, we asked them if they were prepared to test the coupled use of cooling systems. We found that when they were aware that the solution did not harm their comfort and made it possible to reduce energy consumption, they were almost all prepared to incorporate coupling into their comfort management practices.

Of those who answered ‘yes’, half of those with an initial set point of between 22 and 28°C thought they could increase their set point temperature with coupling. However, there is still significant room for improvement in raising awareness about the benefits of ceiling fans and their impact on perceived temperature.

Many comments highlighted the potential discomfort in shared spaces, particularly due to unequal access to cooling. For example, a person sitting directly under the air conditioner may experience a different level of comfort than someone farther away, leading to disparities in temperature perception and overall satisfaction.

<figure><img src="image_5.png" /><figcaption>**Figure 4.** Selected temperature setpoint with and without coupling implementation</figcaption></figure>

**4. Discussion**

The study highlights varying practices and habits across the different French overseas territories regarding the use of ceiling with air conditioning.

Most of the answer were recorded for La Réunion. Users in mixed cooling buildings are aware of energy consumption and the benefits of ceiling fans. However, a gap remains between awareness and practice. Many recognize the advantages of combining both systems but rarely apply them due to doubts about effectiveness or lack of control over shared temperature settings. Users tend to adjust ceiling fans to match air conditioning rather than tuning AC based on fan use. In shared spaces, flexible workspace arrangements could help mitigate uneven cooling.

Regarding the few answers received from Guadeloupe and French Guiana, awareness of energy efficiency exists, but implementation is inconsistent. Air conditioning dominates, with reasonable settings, but fan use remains secondary. In New Caledonia, office workers often use both air conditioning and ceiling fans, with a preference for fans during hot periods. However, combined use is rare. Following awareness efforts, all participants expressed interest in experimenting with coupling the two systems and adjusting the temperature settings between 26°C and 28°C.

Behavioural and organisational barriers, such as concerns about thermal or acoustic discomfort and constraints in shared workspaces, also hinder the widespread adoption of these hybrid systems. These findings underscore the need for enhanced education and awareness among users, facility managers, and building designers to fully capitalise on the benefits of hybrid cooling. Early integration of these systems into building design and targeted training can enhance their efficiency.
## 5. Conclusion

The COOLIBRI project explores an innovative approach by linking air conditioning setpoints to ceiling fan use, aiming to reduce energy consumption while maintaining comfort. By exploring how occupants adapt to this system, the project seeks to provide practical recommendations for office buildings.

A key finding from the study is that, following a preliminary survey, users in our sample are open to adjust their habits and raising the air conditioning setpoint above 26°C when using a ceiling fan, even without having conducted any experimentation. However, it was also observed that this willingness to change habits tends to decrease with age. This is encouraging and demonstrates real potential for promoting this solution.

The study also highlights the need for increased awareness and guidance to promote effective coupling practices and to ensure successful adoption. While AC and CF are frequently used together, users often lack awareness of how to optimise their interaction. Many do not adjust AC setpoint temperatures to account for the additional cooling effect of CFs, limiting potential energy savings. To maximise energy savings, technological solutions should prioritise ceiling fan use, activating air conditioning only when necessary, increase air conditioning setpoints when ceiling fans are in use, and be intuitive and user-friendly to encourage widespread adoption.

Additionally, Task 2 of the project, not covered in this paper, involves experimental studies in La Réunion and Guadeloupe to further assess the effectiveness of this integrated control system. These studies include on-site feedback with measurements of energy consumption and thermal. They are currently underway and will be presented in future publications.

As global temperatures rise, these findings may have broader implications, extending beyond tropical climates and influencing cooling strategies in other regions that face increased air conditioning demand.

## References

[1] OECD 2025 *Zero-Carbon Buildings in Cities: A Whole Life-Cycle Approach* (Paris: OECD Publishing) https://doi.org/10.1787/daae8779-en

[2] Raftery P, Cheung T, Douglas-Jaimes D, André M, Li J, Michael Kent M, Huynh Khoa K, Sultan Z and Schiavon S 2023 *Fans for Cooling People Guidebook* https://cbe-berkeley.gitbook.io/fans-guidebook/

[3] Athchaiyajirakul S and Lertsatittanakorn C 2008 Small fan assisted air conditioner for thermal comfort and energy saving in Thailand *Energy Conversion and Management* **49**(10) 2499–2504

[4] Chen W, Zhang H, Arens E, et al. 2020 Ceiling-fan-integrated air conditioning: Airflow and temperature characteristics of a sidewall-supply jet interacting with a ceiling fan *Building and Environment* **171** 106660 (DOI: https://doi.org/10.1016/j.buildenv.2020.106660)

[5] Malik A, Bongers C, McBain B, et al. 2022 The potential for indoor fans to change air conditioning use while maintaining human thermal comfort during hot weather: An analysis of energy demand and associated greenhouse gas emissions *The Lancet Planetary Health* **6**(4) e301–e309 (Elsevier, ISSN: 2542-5196, DOI: https://doi.org/10.1016/S2542-5196(22)00042-0)

[6] Miller D, Raftery P, Nakajima M, et al. 2021 Cooling energy savings and occupant feedback in a two year retrofit evaluation of 99 automated ceiling fans staged with air conditioning *Energy and Buildings* **251** 111319 (ISSN: 0378-7788, DOI: 10.1016/j.enbuild.2021.111319)

[7] Celaire R, Séauve L, Priori V and Sinczak M 2022 *Programme OMBREE, Groupement EQUINOXE – CELAIRE – MS Architecture – INDDIGO* www.Guide-brise.org

[8] Berkeley University 2023 Hybrid Cooling Leads to Significant Energy Savings in Tropical Office Buildings https://vcresearch.berkeley.edu/news/hybrid-cooling-leads-significant-energy-savings-tropical-office-buildings

[9] Région Réunion, LPBS and IMAGEEN 2009 *Référentiel PERENE pour la conception thermique des bâtiments à La Réunion* (Novembre 2009) Référentiel PERENE pour la conception thermique des bâtiments à La Réunion - Imageen