We will be following the construction of a passive house in Haute-Savoie (74), nearAnnecy, from design to completion. The house, with around 210m² of living space, is built of masonry with external insulation. It is located at an altitude of 600m and faces due south.
A passive house does not mean that there is no heating, but that its use is extremely limited. The aim of this project is to achieve a building that requires less than 15 kWh/m² per year of heating, in accordance with PassivHaus standards.
Thanks in particular to its reinforced insulation and airtightness, a passive house offers not only very low heating consumption, but also a high level of comfort. In addition to managing a pleasant room temperature, the "passive" approach takes account of the temperature of interior surfaces and air movements, among other factors.
As the building permit was submitted before 1 January 2013, the owners were not obliged to comply with the RT2012 standard. Instead, they voluntarily opted for the more pragmatic PassivHaus standard.
A few differences between the RT2012 and Passivhaus standards:
The Passivhaus standard imposes a maximum of 15kwh/m²/year for heating, whereas RT2012 imposes a maximum of 50kWh/m²/year in primary energy for heating, air conditioning, domestic hot water, lighting and auxiliaries for heating and controlled mechanical ventilation.
The fact that RT2012 uses primary energy means that it is virtually impossible to use only electric heating (joule effect). The conversion factor for electricity to primary energy is 2.58 according to the RT2012 standard. To simplify, 15kwh/m²/year of electric heating corresponds (arbitrarily) to 38.7kwhep/m²/year in RT2012.
This result is crude because the calculation methods are not the same, particularly in terms of the surface area and temperature taken into account.
For example, RT2012 is based on an interior temperature of 19°, compared with 20° for a passive house. One extra degree means an extra 15% on your heating bill.
In addition, thermal bridges and air tightness are less well taken into account in RT2012;
To put it simply, the RT2012 standard makes certain heating methods compulsory, whereas the PassivHaus standard attaches more importance to the building envelope.
In view of the forthcoming RT2020 - BEPOS developments, it will be simpler to change the heating method rather than the structure of the building if we want to comply with the new standards. But will this really be worthwhile, given the relatively high cost of investing in a heat pump, solar panels or pellet boiler and very low consumption?
These systems can be expensive to buy, and are prone to mechanical breakdowns that wipe out any savings compared with joule-effect electric heating. It was for these reasons, and to gain in comfort, that the owners turned to a passive house.
The design of this villa by architect Daniel DIDIER is based on a PHPP study carried out by the Enercobat thermal design office. Particular attention was paid to the treatment of thermal bridges, air tightness and insulation.
To help achieve the target of 15 kWh/m²/year in heating costs, this house on the outskirts ofAnnecy benefits from a bioclimatic approach, thanks to its large south-facing windows that take advantage of the sun's energy contribution during the cold season. During warmer periods, the house is protected from overheating by a roof overhang and a plant mask to the west, while retaining plenty of natural light.
