What is the purpose of bioclimatic needs (Bbio), as detailed in the RE2020 regulations?
France has expressed its desire to achieve carbon neutrality by 2050 in order to respond to the climate challenge. In this respect, the construction sector is on the front line in terms of protecting the environment and dramatically reducing greenhouse gas emissions, because it is responsible for more than 40% of energy consumption and emits nearly 20% of greenhouse gases in mainland France. Committed to taking action for the climate, this sector is also innovating and rethinking some of its ways of working.
How can bioclimatic needs be defined?
Bioclimatic needs were present in the RT2012 regulations, so are not completely new. In the RE2020 regulations, bioclimatic needs are defined as a way to guarantee that new buildings are constructed to be as energy efficient as possible, while ensuring that users remain comfortable throughout the year. The RE2020 bioclimatic needs calculation includes the building's heating, cooling and lighting requirements. This indicator is mandatory for building permits to be approved.
The RE2020 bioclimatic needs regulation is a coefficient that measures the bioclimatic needs and energy efficiency of a building. It covers new constructions intended for housing, offices or educational establishments Right from the design phase, the features of the terrain are considered, with the aim being that the buildings consume little or no energy for heating and light. With regard to cooling, the "summer comfort" indicator is a new concept. This involves twilight management to reduce solar heat and avoid the use of air conditioning.
The RE2020 bioclimatic needs indicator therefore considers the heating, cooling and lighting needs of a building. However, heating and/or cooling systems or devices which may be installed in time are not included in the calculation.
How to calculate the bioclimatic needs of a building?
The RE2020 bioclimatic needs indicator is calculated by adding together the heating and cooling needs multiplied by two, and then adding the lighting needs multiplied by five according to this formula:
(2 x heating needs) + (2 x cooling needs) + (5 x lighting needs)
The maximum bioclimatic needs (Bbiomax) of a building is a threshold that must not be exceeded. It varies depending on buildings and climatic zones, as it takes into account the location and orientation of the building, the surface and the materials used, and the altitude. These parameters vary greatly across construction projects. When the Bbiomax exceeds its reference value, it will invalidate the building permit application. In the event of non-compliance, the owner is liable to sanctions.
How can you improve the bioclimatic needs indicator of a building?
When the Bbiomax is exceeded, each criterion must be reviewed with the aim of reducing the heating, cooling and lighting needs. A bioclimatic design that improves the energy performance of the building to be constructed must then be considered for the whole project.
1/ Reducing heating requirements
- Have as many south-facing and as few north-facing windows as possible to capture heat from the sun's rays when the outside air is cold.
- Fix thermal bridges (roof, walls and low floors) to counter heat loss by installing thermal breaks, lintels, insulating wall tiles, formwork bricks or external thermal insulation (ETI).
- Control ventilation and sealing, making the building as airtight as possible.
- Improve insulation by increasing its thickness to 300 mm (including roof spaces).
2/ Reducing cooling requirements
- Install solar protection such as roller shutter casings, blinds or sunscreen baguettes.
- Choose high inertia building materials such as terracotta bricks.
3/ Reducing lighting requirements
- Increase glazed surfaces to allow natural light in.
In order to comply with the RE2020 bioclimatic needs standard, the orientation of the building is a fundamental part of the project. When oriented in the right direction, a house makes use of free renewable energies in its direct environment to guarantee a good quality of life for its inhabitants. As a result, spaces that need natural light and heat such as the living room and kitchen should preferably be south-facing to absorb and use the heat of the winter sun. Buffer zones to the north should be used for areas that need no or little heating, such as the garage or cellar.
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