Neural Networks for Predicting Energy Requirements in Multi-Residential Buildings with Hydronic Underfloor Heating Systems

In Europe in general, and France in particular, building systems have evolved considerably over time, from the pre-war period to the industrialization era. Today's housing stock can be divided into 2 main categories: older buildings (built before 1948) and newer buildings built after 1948. The pre-1948 period is characterized by construction in phase with its environment, and can be subdivided into two main periods: before 1850 and between 1850-1948. Buildings constructed before 1850 were characterized by a wide disparity in construction methods, whereas buildings constructed between 1850 and 1948 were industrialized and saw a generalization of construction systems throughout France. These buildings are made of wood, earth, stone or timber, and were designed to be in total harmony with their immediate environment. They take many forms, such as Longères in the countryside, semidetached houses in historic villages, timber-framed houses, Haussmann-style collective buildings in major cities… One of the main characteristics of buildings constructed before 1948 is that they use local natural resources as raw materials. Wood, earth, brick and stone are always present, depending on the region. What's more, the heating system installed in these homes uses two energy sources to operate: wood and coal. Finally, the old building is a construction that has benefited from bioclimatic design, i.e. it has been designed in such a way that the immediate environment is taken into account to optimize its performance: the sunny facade has several openings to the outside and concentrates the living areas. The exterior is devoid of vegetation or buildings that could shade the building. The north-facing facade concentrates passageways such as outbuildings and stables. It has few openings to the outside, thicker walls and is protected by relief and/or lush vegetation. This bioclimatic design means that these homes consume very little energy. The vast majority of them are even rated D for energy efficiency, the average for French housing stock. After the Second World War came the “Trente Glorieuses” (1945-1975). This period of strong economic growth led to an acceleration in housing construction. Two types of housing sprang up all over France: “Habitations à Loyer Modéré” (HLM) and Favier-style suburban pavilions. During this period, the aim was to build quickly, even if this meant abandoning bioclimatic design. Industrial materials such as cement and oil were used, and housing did not benefit from bioclimatic design. As a result, the homes built at the time are considered to be thermal flats, most of them rated $F$ and $G$. 1974 saw the advent of new building regulations. After the first oil crisis, France discovers that it's no good being dependent on fossil fuels. So, France opted for nuclear power, and the French diversified their heating systems. Oil-fired systems gradually gave way to electric heating. It was at this time that the first “Réglementation Thermique” (RT) was introduced. The 1974 RT called for a diversification of construction methods and a focus on building insulation. This marked the advent of Positive Energy Buildings (BEPOS). The RT 1974 marks a turning point in French construction. For the first time, it regulated building design. Its main aim was to encourage individuals to insulate their homes through two types of work: roof insulation and wall insulation with brick lining and an air gap. This first Thermal Regulation was followed by several others, each presenting new work items to be integrated into housing design: the obligation to ventilate in the RT 1982; consideration of domestic hot water consumption in the RT 1988; calculation and limitation of the Primary Energy Consumption (PEC) of buildings for the RT 2000; limitation of PEC and consideration of summer overheating (TIC) for the RT 2005. RT 2012 introduces a new limit on RUE, a new design indicator (Bbio), a thermal study and an air-tightness test. And more recently, from 2022, the advent of the RE 2020 environmental regulation, which imposes 3 main additional objectives compared to RT 2012: to build “low-carbon” buildings over their entire life cycle; to further improve the energy performance of housing by further reducing energy consumption and increasing the production of renewable energy; to ensure occupant comfort during hot weather, while reducing cooling requirements as much as possible. As architectural systems have evolved, so have heating systems. What about underfloor heating? According to the study of remains, underfloor heating has existed since the 4th century B.C. However, this process was abandoned with the fall of the Roman Empire, only to reappear in the 1930s. But this underfloor heating technique was really developed in the 1960s. Water circulating in the floor was heated and transferred to the floor. The air mass in contact with the floor warmed up and rose until the room was heated by convection. Problems arose, however, with occupants experiencing headaches and leg pain, as the floor temperature was too high (over $30^{\circ}\mathrm{C}$). This technique was used for a few years, only to be abandoned again. Today, underfloor heating systems are referred to as “low temperature”. In fact, the temperature of the floor must not exceed 28° C (the average temperature of the arch of the foot). Water circulates in the floor, and the concrete slab stores and radiates energy. There's no accumulation of warm air, which avoids problems of discomfort. Underfloor heating systems can be adapted to all forms of energy production (solar, geothermal, oil, gas, electric, etc.), but particularly to environmentally-friendly heating systems such as geothermal and solar heating. In the 1930s, after the return of underfloor heating systems, some apartment buildings were equipped with hydraulic underfloor heating systems serving several apartments, i.e. one loop for several dwellings. Existing control systems on the market are unable to regulate these cases of buildings equipped with multi-zone loops. The aim of this article is to study possible technical solutions using artificial intelligence to control these types of circuits, thereby improving the energy efficiency of these buildings.