- THE ROLE OF DAYLIGHT IN THE EXISTENT AND FUTURE FRENCH BUILDING REGULATIONS by Christophe Martinsons
THE ROLE OF DAYLIGHT IN THE EXISTENT AND FUTURE FRENCH BUILDING REGULATIONS by Christophe Martinsons
Head of Lighting, Electricity and Electromagnetism division
Centre Scientifique et Technique du Bâtiment (CSTB)
The French building energy code, known as “RT”, French for thermal regulation, aims to promote energy efficiency by requiring an assessment of building energy performance. Since 2000, electric lighting has been formally included in the calculation of the overall building energy consumption, thereby giving an incentive to use efficient lighting equipment and maximize daylight availability in rooms.
RT 2005, the building energy code currently in use, is based on an hourly energy calculation method that uses climatic data input. This lecture will first present the specific method of daylight calculation in buildings. The relationships between daylight and artificial lighting consumption will be detailed. These successive steps are associated with many underlying approximations that will be emphasized in the presentation because they clearly limit the accuracy and applicability of the method.
Compliance to RT 2005 is defined by a set of objectives to be met, each one of them relying on the comparison with a hypothetical “reference” building. This reference building has the same architecture, but is assigned with mandatory materials and equipment characteristics (reference values). In other words, RT 2005 only gives a relative assessment of the building energy efficiency. Despite many improvements, this approach has been criticized for its inability to fully reflect the positive aspects of architectural innovations and progress in the building envelope itself.
The next energy code, RT 2012, is being devised by the governmental building directorate with academic partners, such as the CSTB, and industrial stakeholders. Unlike the current regulation, it is intended to provide an absolute method of energy consumption. Compliance will be based on an overall performance level expressed in kWhPE/m²/year. The target fixed by the government is 50kWhPE/m²/year, which reflects an ambitious commitment to reducing CO2 emissions and saving energy. The future regulation should be applicable as early as 2011 for new tertiary buildings. In 2013, new residential buildings should comply with RT 2012.
This drastic reduction of energy use in future buildings poses serious challenges to artificial lighting. For instance, office buildings equipped with the best available lighting technologies show that lighting consumption exceeds half the 2012 threshold. Today, the most significant ways to reduce lighting consumption are (1) to promote the optimal uses of daylight devices and solar protections, (2) to use daylight-responsive artificial lighting systems with gradation and zoning capabilities and (3) to implement control strategies based on the actual presence of people.
This lecture will show how the RT 2012 lighting calculation method can fix some drawbacks of the current method, while providing a better characterization of daylighting devices and sensor-based control systems.
Christophe Martinsons, Centre Scientifique et Technique du Bâtiment (CSTB). Head of Lighting, Electricity and Electromagnetism division.