Like the 2012 thermal regulations (RT 2012), RE 2020 applies a basic principle of energy efficiency:the cheapest and least polluting energy is the energy we don't consume. With this in mind, the energy requirement indicator (Bbio) is still present, but the regulatory threshold is more ambitious.
Definition of the Bbio index in RE2020
The RE2020 Bioclimatic Needs indicator (or Bbio index) uses a points system to measure a building's energy requirements for heating, cooling, and lighting. It takes into account various building design parameters, such as the quality of its insulation and its overall design (orientation, whether it is a dual-aspect dwelling, etc.). It thus encourages the construction of more energy-efficient buildings and the use of renewable energy sources.
What are the differences with RT2012?
RE2020 takes into account cooling requirements or Bbio cooling, which was not the case with RT2012.
In addition, the maximum threshold for the bioclimatic requirements of housing has been lowered by an average of 30% compared to the previous regulation.
Measurement of the Bbio index
To comply with regulations, the Bbio value of a building must not exceed the Bbiomax value.
The Bbio_maxmoyen requirements for residential buildings are as follows:
- 63 points for a detached or semi-detached house
- 65 points for shared accommodation
Bbiomax is calculated based on Bbiomax_average:
Bbiomax = Bbio_maxaverage ×(1 + Mbgéo + Mbcombles + Mbsurf_moy + Mbsurf_tot + Mbbruit)
With:
Mbgéo = modulation coefficient based on the geographical location (geographical area and altitude) of the building. RE 2020 combines the two modulation factors from RT 2012 (Mbalt and Mbgéo) into a single geographical modulation factor that follows the same principle, namely adjusting the Bbio requirements according to varying climatic conditions
Mbcombles = modulation coefficient based on the floor area of converted attic space in the building. This is a new modulation that allows the Bbio requirements to be adjusted to take into account heated areas with a ceiling height of less than 1.80 m (not included in the SHAB)
Mbsurf_moy = modulation coefficient based on the average surface area of the dwellings in the building or part of the building.
Mbsurf_tot = modulation coefficient based on the total surface area of the building.
Mbbruit: modulation coefficient based on exposure to noise from transport infrastructure near the building (new modulation introduced by RE2020). To take into account cooling requirements in the Bbio calculation, Mbbruit compensates for noise constraints that limit the possibilities for natural ventilation of the building by opening windows (Br2, Br3), which are particularly detrimental to buildings on the Mediterranean coast and in the hinterland (H2d and H3).
What factors can influence the Bbio index?
Several factors can have an impact on the Bbio of RE2020.
One of the main factors is the thermal insulation of the building. Effective insulation limits heat loss in winter and improves comfort in summer, thereby reducing heating and cooling requirements. Considering their phase shifts and benefits in terms of summer comfort, the use of bio-based materials is therefore almost systematic.
Another factor influencing Bbio is the optimization ofthe building's orientation. Indeed, promoting adequate solar exposure can also help reduce the building's energy requirements.
Finally, other levers include managing glazed surfaces to promote natural light while avoiding overheating,using materials with high thermal inertia to regulate temperature variations, and ensuring the building is compact to reduce heat loss.
A high Bbio rating is achieved by optimizing the building structure independently of the energy systems used.
The Bbio index is an indicator used to measure the energy requirements of a new building. It takes into account specific characteristics such as thermal insulation, orientation, and the building's glazed surface area. Under RE2020, the Bbio must be considered in combination with other indices such asthe Cep index (primary energy consumption) to assess the overall energy performance of a building.
