French Thermal Regulation RT 2012
Since they were first introduced in 1975, the French Thermal Regulation (RT) has been developed and strengthened several times. Within France’s Grenelle de l’Environnement framework, the goal of RT 2012 is to reduce primary energy consumption by 150 billion kWh (150TWh) between 2013 and 2020, and CO2 emissions (i.e. greenhouse gases) by between 13 and 35 million tonnes (depending on the method) over the same period. RT 2012 came into force on July 1, 2011 for the tertiary sector and will be applied from January 1, 2013 in the residential sector.
Because of their energy efficiency requirements, the French Thermal Regulation influences the choice of energy used in buildings. At present, as shown in the graphs below, gas and electricity are the main sources of energy use for heating in homes: in 2010, 34% of homes were heated with gas and 30% with electricity.
Types of energy used for heating by type of housing ( Source : INSEE, SOeS )
The RT 2012 provisions
The RT 2012 provisions revolve around three coefficients used to monitor bioclimatic requirements, summertime comfort and primary energy consumption in residential buildings.
- The bioclimatic coefficient Bbio is a new indicator introduced along with RT 2012. It measures the building’s efficiency in terms of the need for heating, air conditioning and lighting, regardless of the energy systems in place. This coefficient reflects the building’s performance with regard to thermal exchanges and the sun’s contribution as a source of heat and light. The building’s insulation, geometry and orientation, together with its total window area, are all key factors in achieving a bioclimatic coefficient below the maximum value set by RT 2012. The Bbio maximum is adjusted to take account of the building’ type, geographical location, altitude and surface area.
- The requirement for summertime comfort in buildings without air conditioning is the same as in RT 2005. For certain types of buildings defined by the RT, air conditioning is not needed in summer. In these buildings, a threshold temperature Tic must not be exceeded for five consecutive hot days.
- The consumption requirement covers five key areas of a building’s energy consumption: heating, cooling, lighting, hot water production and auxiliaries (pumps and fans). Under the Grenelle 1 Law, maximum annual energy consumption Cepmax is set at 50kWh per square metre. This consumption is calculated for primary energy and not final energy as it was with RT2005. The conversion factor between final energy and primary energy is 2.58 for electricity and 1 for other energy sources. This requirement is adjusted to take account of the building’s geographical situation, type, altitude, surface area and CO2 emissions.
The adjustment for CO2 emissions applies only to heating from biomass and heat networks, and can only be 30% higher than the initial maximum. In addition, it is compulsory for individual houses to produce renewable energy. To
sum up, the purpose of the bioclimatic coefficient is to maintain building consistency and, on the basis of external factors such as temperature and solar radiation, to determine the needs that energy systems will be required to cover. These needs must generate average annual consumption of less than 50kWh per square metre, whilst providing a comfortable indoor environment.
RT 2012, a gas friendly regulatory framework
While the goal of reducing primary energy consumption in every new building is clearly stated in the text of RT2012, the same is not true for greenhouse gas emissions. Although reducing energy consumption in itself helps to reduce such emissions, we note that there is no maximum emissions goal set in RT2012, and no differentiation between the different heating methods (apart from the adjusted consumption requirements for wood fuel and heat networks). However, as the graph below about carbo content of common fuels shows, traditional heating methods do not all have the same CO2 emission rates:
Despite the lack of such differentiation, basing the calculation on primary rather than final energy consumption gives gas a competitive advantage over electricity. The consequences of this new regulation have already been observed, as is shown by the trend in installations of gas and electricity in new houses:
Rate of inclusion of gas and electricity in new housing ( Source : Batim Etudes )
It is likely that this trend will continue over the coming years, as RT2012 begins to be applied to the residential sector. The use of biomass, heat networks and geothermal energy is also likely to increase in the coming years, given their energy and environmental efficiency.