Working through RT2012

These are the headings on the RT2012 form. 

  1. Administratif. This is where the address, owner details, and the cadastre info relating to the plot along with any third-party project management or architects are listed. 
  2. Surfaces. List the Surface S.RT (m²) and the Surface habitable (m²). The Surface S.RT can be calculated later – just put «à calculer» in the field.
  3. Enveloppe. For details about the exterior walls (façades), ground floor
    (plancher bas) and roof space (plancher haut) . This is all about insulation and how you plan to remove any thermal bridges.  Also any internal floors (plancher intermédiaire). If you have any external buildings (garage, etc.) you should also provide details.
  4. Ventilation. Here there is a list of products you can select from. This section assumes that your house is sealed to the outside and that  
    in order to maintain an ambient temperature in your home you will adjust the controls on your ventilation system rather than open a window. With a GREB house we are not sure this is necessary so have said as much on our initial submission. We stand to be corrected! If it is needed, we’ll be interested in the lowest tech, cheapest and least obtrusive system. The choices in this category are: Couple avec ECS (simple flux), Double flux, and Simple flux.
  5. Menuiseries. Windows. For this section it’s necessary to list the makes and the models along with the Uw values, if available. Also the same info for any doors to the exterior (portes d’entrées).
  6. Chauffage principal. This is for your main source(s) of heat. As I understand it a single log burner is permitted as the main heat source up to a maximum floor space of 100m2. If the house is larger than that additional heat sources are required. Because our current plan is 120m2, we’ve spec’d for electric radiators in the upstairs bedroom and in the bathroom. Whether we put them in or not…
  7. Chauffage secondaire. For any secondary heating systems that will be put in place.
  8. Eau chaude sanitaire (ecs). How will you heat your hot water? There are lots of options (Gas, solar, etc.) but we’ve decided on a thermodynamic boiler, which uses heat from the air to warm the water and is said to reduce water heating bills by up to 80%.
  9. Plan de masse. This is the position on the land showing N-S orientation, surrounding boundaries, etc.
  10. Plan de niveau. This is the floor plan.
  11. Plan de coupe. This is for the facades (north, south, east, west). 


Green Energy Suppliers in France

One of the requirements of RT2012 is that all new builds must include a solar-power element. This can mean investing in micro-generation system for your own land or property, choosing a low-carbon, low-energy heat source as your main form or energy. But there is also a third option, which is great for those of us who are on tight budgets. That option is to commit to using an energy supplier that obtains at least 50% of their energy from green sources (solar, wind, water, etc.)

So how to find these? 

There’s quite a list in this article here but also this recent article which gives an overview of Greenpeace’s assessment of the main suppliers in France. Looking at the two lists I would think that you could pass RT2012 by signing up for EDF’s green tariff but according to Greenpeace you’re probably being greenwashed and unlikely to be actually buying energy generated from renewable and non-polluting sources.

One of the companies I lik the look of is There’s also, which also has non-capitalist credentials. Enercoop has a similar feel to Green Energy, which is the company we used in the UK and is also a cooperative. 

You might be thinking well, how green is it really to be buying energy from a company, but this recent article from the Centre for Alternative Technology suggests that connecting to the grid is a better solution than going off grid. It’s worth remembering that all technology has an environmental cost. Also, if you are generating energy that you are contributing to the total amount of green energy that is available for sale to others who perhaps don’t have the means to invest in solutions themselves. If green electricity is flowing in, the demand that needs to be met by dirty energy (and in that I include nuclear) is reduced. Which also feeds into this article about how being green has become something we do (and get to feel smug about) on an individual level when really collective action is needed.

There’s more info on packages with suppliers for auto-consommation (self-generation) here

Ilek seem to have a comprehensive calculator on their site, giving info on expected payback times and also taking government grants into account.

RT2012 recommended wood burners

Rika Impera XL
88% efficient
6380 euro

Rika Imposa 
86% efficient
4380 euro

Rika Jazz
83.1% efficient
3.5 to 7 kW
4400 euro

Rika Twist
79.3% efficient
3552 euro

Invicta Odysee
50cm logs
raccordement direct d’un conduit pour l’arrivée d’air frais extérieur
12kW 1475 euro

Invicta Onyx (it’s an inset)
71cm logs
2600 euro

Invicta Pharos
No exterior air
40cm logs
1599 euro

Deville Emeraude
36cm logs
1389 euro

Deville India
exterior air I think
979 euro

Deville Grand Safir
50 cm logs
1176 euro

Godin Galatea
33 cm logs
2161 euro

Jotul F162 (F160),50-799.htm
33 cm
1539 euro

Jotul F480
30 cm logs

33cm logs
2580 euro

50cm logs
GBP 2699

Palazzetti Irene
3179 euro

Supra Ontario 4
2459 euro

Supra Quattro
1617 euro

SUPRA Ulysse
No exterior
1199 euro

MCZ Thor (all the oxygen used for combustion is taken outside)

MCZ Chari (all the oxygen used for combustion is taken outside),260,MCZ,Chari.php
1300 -> 1800 euro

MCZ Bahr
1300 euro (estimated)

MCZ Nogal

Choosing Windows

How Many

To meet RT2012 we need 1/6 of the floor space of the house to be windows. Our current plan is about 120m2 so that means about 20m2 of windows.


The two important U values for windows are:

  • Ug for the glass
  • Uw for the entire window

What Material

I really like the look of wood and aluminium, but since the plan is to build a mortgage-free home within our budget, they are out of our reach financially. As is triple glazing. So we’re looking for double-glazed uPVC.

Luckily the U values for uPVC seem to be better than for wood (pine, anyway. Oak is way out of our reach.) Given our remit is to build the warmest most insulated house we can on our 100K budget, uPVC it is!

There’s some good info about that on this website.

What Size?

We want the biggest windows we can afford! It looks like there are some standard sizes (based on price) so it may be that we have to base our decision around that. 

Window Suppliers

Much research to do on this front as the prices and u-values vary widely.

Also want to see what price a 3-pane window with a central opening pane (the two outer ones fixed) compares to a 2-pane one.

Woodburning Stoves

The recommendation for a 120m2 house is a 10kW stove.

The stove we need must be one that supports a direct, external air supply – in French it’s raccordement air extérieur (directly translates as external air connection) – generally done through 125mm ducting. 

Some potentially useful discussion on pistonheads.

The external flue needs to rise to 0.4m (40cm) above the max height of the roof according to building regs.

Our preference is for one that takes 50cm logs.

Enterprise Etude Thermique

Researching companies that will carry out the Etude Thermique (Thermic Study) for our come and provide us with the certificate of conformity to RT2012 to add to our Permis de Construire document.

  • Etudes thermique RT 2012 (Calcul du coefficient Bbio)
  • Attestation RT 2012 obligatoire pour votre permis de construire de construction neuve ou d’extension
  • Récapitulatif des minimas d’isolation à respecter

135 Euro

This is the one that An used and paid 199 Euros for. 

Pack Fin de travaux 199 €, includes:

Etude thermique RT 2012
Calcul du Bbio, du Cep et de la Tic
Délai de 7 heures ouvrées
Quelle que soit la surface
Etude certifiée
Décennale – RGE OPQIBI
Attestation du permis de construire
Dimensionnement des puissances de chauffage pièce par pièce et ECS
Modifications de votre étude
gratuites & illimitées
Conseils du thermicien
Par téléphone et messages
Calcul des énergies grises
Attestation de fin de travaux
remise des fichiers pour son édition