What about heat comfort? It is not just a matter of temperature. In cold winters, in poorly heated houses, one could supply heat directly to the body. It sounds absurd but this is Slowheat. SlowHeat’s crazy bet is to reduce domestic heating consumption. Without any loss of comfort and efficiency. Is it possible? Actually, SlowHeat is an interdisciplinary and participatory research project involving 29 households in Brussels between 2020 and 2023. It is by no means just academic reasoning. Nor a theoretical approach through abstruse calculations. This research is based on concrete results. There are obstacles and challenges to overcome in order to extend the practice of so-called ‘slow warming’. To explore the path of moderation even in the thermal comfort of the home.
Household heating is a major contributor to energy consumption. The Slowheat project is based on a differentiation of the comfort needs of individuals and buildings. It is implemented in a three-year interdisciplinary workshop. Based in the real world and focused on adaptive heating practices. The initiative involved 23 households in Brussels, Belgium and was coordinated by researchers at the University of Leuven. In a collective exploration of indoor comfort sufficiency. To minimise heating and meet the requirements of environmental thermal balance.
From an average thermostat setting of 19°C, the participants progressively reduced their core temperature to a long-term average close to 15°C. Through adequate warming of the individuals through personal comfort systems, clothing and physiological adaptation. This led to a 50% reduction in heat consumption. With consequent savings in electricity consumption. The qualitative analysis highlights the multiple dimensions of social practices related to heating. And emphasises the key influence of control and comfort in sustaining significant temperature reduction.
Critical points
It was not easy. Fear of the cold, fear that neighbours or friends would no longer want to visit. Anxiety about conflicts within the flat or the family.
‘In the beginning, it was necessary to overcome fears,’ the researchers admit. Some habits are more complicated to adopt than others. Like the pedal board installed under the desk, which allows one to keep moving even while working. The researchers acknowledge that their project is not a miracle solution applicable to everyone. But they defend the need to rethink our habits and our relationship with consumption, and therefore with energy. ‘The goal is not to tell people that they will be cold. Their idea is to maintain the same level of comfort but with a few degrees less,’ explains Amélie Anciaux, sociologist at the University of Leuven and member of SlowHeat.
The goal isn’t to tell people that they will be cold. The idea is to maintain the same level of comfort but with a few degrees less
The issue of interior temperature
Heating of living spaces is by far the largest source of energy consumption in European households. At EU level, the residential sector accounts for 27% of final energy consumption. Of this 64.4% is related to heating inside rooms (EUROSTAT 2024). Consequently, efforts are concentrated on reducing this consumption. By acting on the upgrading of buildings through energy renovation. By focusing on energy efficiency. But none of these principles address the concept of sufficiency. As a consequence, the strategies developed also neglect this approach. For example, although the rehabilitation strategy in the Brussels region identifies non-technological solutions as potential levers, related actions are limited to communication and accompanying measures without any quantitative targets.
For that matter, research on indoor temperature in residential environments is largely limited to health risk situations. Such as overheating during heat waves or unhealthy living conditions associated with energy poverty in winter. An overwhelming focus on efficiency over sufficiency. A recent meta-analysis of scientific articles on this subject concluded that individual needs are highly variable. To the point that it is not possible to define what a warm and healthy temperature should be. Although this may sound bizarre.
Warm up the body
Alternative approaches related to thermal well-being ( in particular the theory of alliesthesia – from alliós – to change and aísthēsis – sensation, perception) emphasise thermal pleasure rather than mere isothermal neutrality. Providing a conceptual framework for the creation of pleasurable yet non-uniform environments. This theory suggests that pleasure arises from environments with contrasting rather than uniform thermal conditions. For example, a slightly cold environment combined with direct heating of specific parts of the body. In other words, this approach focuses on heating the body rather than the building. The concept of warming the body, according to adaptive comfort theory, is the ability to adapt behaviour, expectations and physiological responses to the environment. To achieve thermal comfort. Highlighting the distinction between involuntary physiological adaptations and voluntary actions triggered by discomfort.
The approaches are different. And they range from changes to the indoor space to the creation of customised, small-scale thermal zones. This includes dedicated heat flows to specific parts of the body. More recently such devices known as personal comfort systems (PCS) such as heated blankets, radiant panels, heated chairs, etc. have been developed and tested. PCS have been shown to compensate for reductions in room temperature of several degrees in offices, saving energy while providing greater comfort than overall indoor air heating. However, until now, no comprehensive research had explored the impact of PCS in residential settings.
Communities
However, in the real world, the Slowheat project proposed the old idea of heating the body rather than the house. It directly explored solutions such as personal comfort systems (PCS).
PCSs have proved to be important opportunities for adaptation and have triggered a change in heating habits. But PCS alone are not sufficient to support these changes. The collaborative approach proved essential in framing the research community that has developed adaptive heating practices.
It was about first learning to understand the signals of one’s own body. And then to rely on one’s involuntary physiological responses and conscious ability to adapt through environmental, technical or behavioural solutions. This community and the theoretical background it developed gave participants confidence. As essential as the technological dimension for further dissemination of this warming practice.
Average temperature
The average indoor temperature chosen by the participants at the end of the project was 15.1 °C. While the average thermostat setting before the project was 19 °C. Heating consumption decreased by an average of 50 %. Although part of this reduction hides heat flows from neighbouring heated rooms. Electricity consumption decreased by 14% despite the use of PCS. The cost-of-living crisis that occurred during the project probably induced electricity-saving behaviour that offset the electricity consumption of PCS. Although several limitations have been identified regarding the generalisation of these figures, they indicate an energy-saving potential.
Finally, this research has contributed to the discussion on the sufficiency of heating practices. It supported the idea that the basic need for thermal comfort should not be equated with domestic heating, which is only one way of addressing it. In this experiment, the positive approach of sufficiency (to provide a sufficient level of comfort and well-being) was not at odds with the negative approach (to reduce current levels of energy consumption).
For more information: Slowheat
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