Housing energy performance: RE2020 less demanding than RT2012

La publication des textes de la RE2020 pour enquête publique a permis de calculer les exigences de performances notamment énergétiques. Verdict: la RE2020 serait plutôt en retrait par rapport à la RT2012.

The number of RE2020 indicators has experienced high inflation compared to RT2012.The project of decree on energy and environmental performance requirements, - which still has 49 pages, 52 articles and 12 annexes - posted for the public inquiry, in list no less than 9 in its articles 6 to 8::

Among these 9 indicators, only 6 of them-Bbio, CEP, NR, CEP, Icenergie, ICComposants and DH-must be lower than maximum values for the building to be regulatory.The other three - icbâtiment, Stockc and UDD - are only indicative, for the moment.

Two RE2020 indicators already taken into account in RT2012

Among these 9 indicators, only two - Bbio and CEP - already existed in RT2012 and reflect the required energy performance of the building.The BBIO expresses the performance of the envelope.The CEP adds the efficiency of the technical systems installed in this envelope to calculate conventional energy consumption: lighting, heating, refreshment, production of domestic hot water, mobility of the occupants internal to the building in the case of the collective and the tertiary sector,heating, cooling, domestic water and ventilation auxiliaries.

Consequently, it is possible to compare their maximum values - the ceilings which should not be exceeded for the building to be regulatory - in RT2012 and in RE2020, as they emerge from the texts put in the public inquiry.You must naturally take many precautions for this exercise.

Indeed, several important points have changed between RT2012 and RE2020.

Evolution of weather files and new refreshing needs in the RE2020

First, the BBIO and the CEP of the RE2020 contain refreshment needs.Which was not the case in RT2012 and, mechanically, increases the values of Bbio and CEP obtained in RE2020.The calculation of the surface used in RT and RE has evolved: these are no longer the same m².

The weather files have evolved too and take into account the average climate to come, rather than the average climate.In RE2020, the CEP includes, for the collective and the tertiary sector, the consumption of internal mobility which did not exist in RT2012.In short, the BBIO and the CEP RE2020 contain more things than their predecessors in RT2012.

The exercise of comparison of the BBIO and CEP between RT2012 and RE2020 is therefore perilous.It is still necessary.To carry out it, it would be necessary with the same building, carry out the RT2012 study and the RE2020 study, in different climatic zones, for different altitudes, ... and renew the exercise for different types of building: individual house, building ofcollective housing, etc..

We do not yet have certified RE2020 calculation software.They will only be accessible after the final publication of the texts and the RE2020 method, at the end of May or early June.In the meantime, it is possible to carry out some simulations starting from the versions of the calculation engines available today and at the cost of some binding hypotheses.

Comparison of BBIO and CEP in RT2012 and RE2020

The Bbio_max formula in the RE2020 is:

Bbio_max = bbio_maxmoyen x (mbgéo + mbcombs + mbsurf + mbbruit).In the case of RT2012, it was perfectly possible to enter the bbio-max calculation formula and calculate it.This is no longer possible with the RE2020, since the new calculation formula contains data from the RE2020 calculation engine itself.

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Take the different terms, one after the other.For bio_maxmoyen, it's easy.As indicated by Annex IV, page 37, of the draft "requirements" published in public consultation, the BBIO_MAX_MOYEN is 63 for individual or attached houses and 65 points in the case of collective housing.Note in passing that distortion in favor of overconsumption in collective housing is always present.Then, the values for offices and teaching premises are not yet published.Our entire exercise can therefore only focus on individual houses and collective housing.

An exercise applied to individual houses and collective housing

The Mbgéo coefficient is classic, takes into account the climatic zone and the altitude, and varies, for individual houses, from 0.9 to less than 400 m altitude in zone H3 at 1.85 to more than 800 maltitude in the H1B zone.There is still a small inconsistency.This coefficient, for a given climatic zone always increases with altitude, except in zone H2C where it is 1.5 between 400 and 800 m altitude, but drops to 1.35 beyond 800 m.No doubt a writing error in the document put in consultation.

Pour les immeubles collectifs, Mbgéo affiche des valeurs de 0,85 (< 400 m, zone H2c) à 1,85 (> 800 m, zone H1b).Without noticing inconsistency in the H2C zone.The following simulation focused only on an altitude of less than 400 m.

The Mbcombs coefficient, intended to take into account the presence of fitted attic, requires values from the calculation engine: the SREF reference surface and the fitted attic surface whose ceiling height is less than 1.8 m.The Mbcombs calculation calculation formula is identical in individual and collective house: mbcombs = (sref + 0.4xscompes)/sref.In the simulation, Screlles is equal to 0 and the Mbcombs coefficient is therefore 1.

Mbsurf, pour sa part, varie en maison individuelle, selon que Smoylgt (surface moyenne du logement au sens de la méthode de calcul RE2020) est > 100 m², comprise entre 100 et 150 m² ou > 150 m². En logement collectif, la méthode propose 4 tranches de Smoylgt : ≤40 m², de plus de 40 à 80 m², de plus de 80 m² à 120 m² et > 120 m².In the simulation, SMOYLGT varies from 100 to 200 m² in an individual house and systematically worth 50 m² in collective with 5 to 80 dwellings per building.

Mbbruit depends on the noise areas, BR1, BR2 and BR3, which are conceptual areas to be established for each project, rather than geographic areas within the meaning of climatic zones, for example.For the individual house, Mbbruit is worth 1 everywhere, except for areas BR2 or BR3 located in the climate zone H2D or H3 where it is then worth 1.1.For collective housing, Mbbruit is worth 1, except in exposure BR2 and BR3Où it is worth 1.1 in zones H1C and H2C, 1.2 in areas H2D and H3.

The calculation of the CEP_max is described in Part III of Annex IV, from pages 39 to 41, to the party indicated Page 7, article 13: CEP_max = CEP_maxmoyen x (McGéo + McCOMBLES + MCSURF + MCBRUIT).The same article 13 also indicates the calculation formulas for the CEP, nr_max (= cep, nr_maxmoyen x (mcgéo + mccombs + mcsurf + mccat)), as well as for icénergie (= icénergie_maxmoyen x (mcgéo + mccombs + mcsurf + mcbruit))))).

The weighting coefficients are known, except the new MCCAT which is a "modulation coefficient according to the category of external constraints of the building".But, surprise, McCat is not otherwise specified, we do not know its value.A research in the text of the project of order requirements gives only two occurrences of "McCat": its presence in the formula for calculating the CEP, NR_max and at the top of the definition above.Nothing in Annex IV which however contains the definitions and methods of calculation of all the other modulation coefficients.Obviously, that does not facilitate the comparison between the CEP RT2012 and the CEP RE2020.We therefore limit ourselves to a comparison between the BBIO indicators.

The tables published below are more indications than values to be taken at the foot of the letter.They invite the debate, but still indicate a direction: the RE2020, from the point of view of energy performance is not very demanding.

Here is the calculation of the Bbio_max ceilings for individual houses according to the RE2020.Above, the surface of the house, on the left the climatic zones.In the middle, the various values of Bbiomax obtained.

This first table must be compared to the second below, which shows the gap, by climate zone and by individual house surface, between the BBIO-Max RT2012 and the BBIO_MAX RE2020.All boxes comprising positive values indicate that, for this specific case of climate zone and house surface, the BBIO_MAX RE2020 is higher than the BBIO_MAX RT2012.On the contrary, all trades with negative values translate a more demanding BBIO_MAX in RE2020 than in RT2012.

This table has 128 boxes, but only 4 with negative values.@Clément Jaffrelo

Same exercise for collective housing: calculation of BBIO-Max values according to the RE2020.The average housing area is always 50 m².The upper line indicates the number of housing in the building.

This time, the bottom table, whose values are however calculated compared to the RT2012 formula with the derogation of 57.5 kWhep/m², always in force for collective housing, compared to the 50 kwhep/m²In individual house, does not show any negative value: the Bbio-Max in collective housing according to the RE2020 is always higher than that which is calculated in RT2012.The largest differences appear for small buildings (5 dwellings).@Clément Jaffrelo

RE2020 objective: decarboner rather than consuming less energy

If the direction indicated by the above tables is verified, all those who complained about the crazy requirement of a BBIO-30% in RE2020 compared to RT2012 can be reassured: we are very far away.The effect of the RE2020 is elsewhere.

If we understand the texts and results of these first simulations, the RE2020 would above all be an effort to decarbonize the buildings.But from the point of view of her method, she turns her back on what all the rest of Europe 4 do: initially reduce energy consumption as much as possible, then decarbonize by asking the ENR to satisfy the balance of theEnergy needs of buildings.

Through the Re2020 texts put in the public inquiry, it seems that the bias is mainly to decarbonize first, in particular through the indicators on the carbon content of the materials and energies consumed, while allowing levels of consumption of consumption of'relatively important energy.

The reduction of 2.58 to 2.3 of the conversion coefficient of primary energy, as well as the drastic drop in the carbon content of the KWH of electricity consumed for heating - it was divided by 2.3 to reachnow 79 GCO2/KWH - powerfully support the cause of electricity.

This will lead to a modification of the energy mix, constructive systems, heating equipment and DHW production used in new construction.There are 4 "useful" energies in the RE2020: electricity, wood pellets solar thermal for heating, not for domestic hot water, and heat networks that benefit from a respite.

Exclusion of gas and boost to electricity with the new regulations

This new method leads to the exclusion of gas from 2025, the disappearance of thermodynamic water heaters, the condemnation of the thermal solar used in CESI (individual solar water heater) for the production of hot water according to Uniclima andEnerplan, the development of heat pumps and connection to heat networks, etc..On the structure side, this method, subject to more precise calculations which remain to be accomplished, promotes wood structure in all its forms and weighs on other solutions.

At the end of the day, the performance of the building translated by the BBIO drops little, or even increases in many cases.The powers necessary to compensate for heating losses therefore remain relatively important.Is this really the right choice?

We must wait until the publication of the final texts, then those relating to the tertiary sector, to have the end of the story.Unless, perhaps, that the complementary label developed by the sustainable building plan is responsible for reducing new construction consumption, for voluntary contracting authorities who wish to adopt it.

Source: Batirama.Com / Pascal Poggi