The building of the future will produce its own energy
In these times of COP 21, solutions to reduce greenhouse gas emissions inevitably require reflection on the building sector. In France, according to World Bank data, nearly a quarter (22.5%) of CO2 emissions are attributable to residential construction and commercial and public services. Since the beginning of the 2000s, French legislation has been strengthening in an attempt to limit this worrying observation; RT2012 in particular imposes strict requirements for new buildings, in order to limit their energy consumption as much as possible. The short-term objective is to switch from 2020 to “positive energy” buildings.
What is a positive energy building?
A positive energy building (BEPOS) indicates its ability to produce more energy than it consumes. This principle involves the recovery and self-production of energy, according to a multitude of processes: photovoltaic and solar collectors, heat pumps, wind turbines, reuse of rainwater, electric storage batteries, etc. In addition to the elimination of greenhouse gas, BEPOS ensures an impressive reduction in costs, and, on the same operating mode as buildings already equipped with photovoltaic sensors, should make it possible to resell the excess energy produced.
In addition to this dimension of so-called positive energy, the BEPOS must also take into account its carbon footprint, that is to say the environmental impact throughout its life cycle, since its construction. This footprint must be reduced to a minimum, which again requires the use of multiple processes: use of ecomaterials with a very low carbon footprint, maximum thermal insulation and powerful airtightness.
From RT 2012 to RT 2020
If the concept of positive energy building has existed in theory since the 1970s, its application requires both efficient technological solutions, and also a strong desire to promote renewable energy, which at that time was not really the primary concern. Faced with the major challenges imposed by the rapid degradation of the climate, BEPOS now appears to be one of the most effective and necessary solutions to try to curb greenhouse gas emissions.
The previous “RT” (thermal regulation) of 2012 already severely limits the energy consumption of all new new buildings, on the principle of “low consumption buildings” (BBC). The consumption limit is therefore currently set at 50 kWh / m² per year. The advent of BEPOS with the future RT 2020 will push the concept of "clean building" to its peak, forcing all new buildings to produce more energy than their consumption. The regulations will however be limited to this energy objective, leaving free rein to the imagination of architects to achieve it.
Copenhagen, European capital of BEPOS
In France, the BEPOS concept is still limited to a few precursor buildings, inaugurated since the beginning of the 2010s; the best-known example is probably the Green Office in Meudon, presented as the first large-scale French BEPOS. In September 2015, an “eco-district” even saw the light of day in Lyon. The work of Japanese architect Kengo Kuma, this island called Hikari ("light in Japanese") is still unique in the world, and should over the years include residential apartments, shops and offices, all BEPOS certified.
Several northern European countries have, however, already taken a comfortable lead over France in terms of positive energy buildings; Finland, Norway, Denmark and even Germany have several thousand. Denmark is a pioneer in this area. The capital of Copenhagen, which plans to build more than 36,000 new homes by 2020, has given priority since the early 2000s to low-consumption buildings and BEPOS.
Coupled with a policy of massive development of electric vehicles in the city, Copenhagen today has a flattering reputation as the most environmentally friendly European capital. Riding on its success, the Danish capital even intends to become a "carbon-free" city in ten years, which would constitute a world first.