Energy efficiency, uses and comfort

"Technologies do not stop people from taking action" says Christophe Beslay. User practices have a considerable impact on the energy consumption of a home and are a source of uncertainty which reduces the reliability of forecasts. According to the author of "Pratiques sociales et modes d’habiter", to guarantee both user comfort and energy efficiency, the challenge is to find solutions that feature responses to the needs for comfort and usability, best consumption practices and economical technical solutions.

Energy efficiency can only be achieved by combining efficient technologies and devices with compatible usage practices. It is therefore necessary to know how to predict the needs, expectations and aptitudes of occupants in order to assess the real performance of a building. Comfort and ease of use are essential conditions for the occupants, which can hamper energy efficiency if the technical systems are not suited to their skills, daily activities and expectations in terms of comfort.

Retain heat and freshness

At the end of the 19th century, it was recommended to keep indoor temperature below 16°C for health reasons, probably because of the pollutants emitted by wood and coal heaters. Between 1986 and 2003, ADEME observed that expectations in terms of well-being were increasingly taking precedence over concerns about consumption costs with an average increase in the temperature of homes from 19°C to 21°C. More recent studies (CREDOC, 2012) show that 30% of households heat the living room to 21°C and 75% to more than 19°C. The bedrooms are heated to over 19°C in 50% of the housing units. When the temperature is restrictively limited to 19°C, which complies with the regulations, the occupants tend to equip themselves with auxiliary heaters. There is a gap between technical standards and social conventions which means that even the most efficient equipment does not produce the expected performance. Satisfactory winter thermal comfort in low-consumption housing requires new practices and, in particular, users should opt for heat conservation and recovery, for example by limiting the opening of windows and using sun exposure.

Example of inhabitant's overconsumption of energy

Other more proactive practices ensure thermal comfort in summer. Some habits, such as ventilating at night or closing windows and shutters during the day, can protect against the heat. Although these practices have been developed and are widely known in the south, they have yet to gain acceptance in the northern regions. In addition, certain factors such as outside noise and the risk of intrusion can prevent the occupant from ventilating at night.

Thermal comfort depends on the measured ambient temperature, but also on the perceived temperature which results, among other things, from humidity, air flows, colours of materials, furniture, light, clothing, food and activities. Like any subjective perception, the feeling of temperature is also related to socio-demographic and cultural factors such as gender, age, membership of a socio-economic or ethnic group. In a shared space, negotiations and compromises between occupants will determine whether everyone’s comfort expectations are met. Energy efficiency will also depend on what Dominique Desjeux calls the “war of buttons” to control lighting and the “war of fire” relating to heating.

High-performance technology is tailored to its user

Energy management systems are becoming increasingly sophisticated. But at the time of operation, a technical system escapes the control of its designers and it is the users who appropriate it. This appropriation depends on the complexity of the technical objects and their usability. The occupants give up using overly complex technical solutions that they cannot master. Also the past experiences of users and their technical skills have an impact. So, the person who is accustomed to collective heating is likely to be in difficulty in a new accommodation with individual heating. In a 2018 study on households suffering energy poverty, Christophe Beslay and Romain Gournet observed that certain fragile households had fallen into poverty and failure to pay energy bills following a move to a home where they could not use the consumption management equipment properly. The process of appropriating new technical systems only takes place when there is transmission of knowledge via user manuals and an on-site learning phase.

Example of non-accessible technology for elderly people

The challenge is to design housing for and around users. Occupants can actively contribute to energy efficiency, but they are above all users with their own priorities, daily routines, and household knowledge. Connected and intelligent housing are solutions to better take into account the inhabitants when the energy management systems are able to interact with the occupants, to adapt to their needs and to multiple action scenarios. Modelling, the “Internet of things” and machine learning will provide a better understanding of housing occupancy and uses. However, the support and participation of occupants in the design through surveys and workshops remain important to achieve a balance between environmental transition, well-being of inhabitants, financial costs and constraints of the territory.

FIND OUT more:

Christophe Beslay, “Pratiques sociales et modes d’habiter”, in Bruno Peuportier, Fabien Leurent, Jean-Roger Estrade (Coord.), Éco-conception des bâtiments et des infrastructures, Volume 2, Presses des MINES, Sustainable Development collection, 2018.

Christophe Beslay and Romain Gournet, Stratégies de traitement des impayés d’énergie. Survey of 14 households, Observatoire National de la Précarité Energétique, 2018.