Trying to make French Regulations on Energy Efficiency and Insulation Easy!!! Part 1: R Values - 05.11.2017

So, both Jon and I completed the 3-day RGE course in January 2017. The task was easier than anticipated, considering it was completely in French (although our teacher spoke a little English). We learned some very interesting facts and important regulations for the business, which we are now putting into practice and hopefully, in the not too distant future, Qualibat will come and inspect one of our ‘Chantier’ to make sure that we are doing things correctly…Nail biting stuff, I know!

Anyhow, I got to thinking about how this information seems to be available to all, yet impossible to find if you don’t really know what you are looking for. I see quite frequently discussions on various Facebook sites where people ask advice and are given advice from the general community, but is it always good advice? Don’t get me wrong, I think these forums are invaluable for people to discover what life is really like living in France for those who have just arrived or those needing a boost to make the leap, however, it worries me slightly that one simple question, such as ” which insulation do I need to insulate my roof?” Can produce in the region of 25 responses, all slightly differing from the previous well meaning ‘expert’.

SO, I am going to try and share some of the rules, regulations and revelations we have learned (and are continuing to learn) here at Maison Bretagne, which are straight from CAPEB. The Artisans of the Building Trade Guild.

For my first sharing blog I will try and explain a little about energy efficiency, in particular insulation, and what the requirements are concerning the ‘R’ value of the insulation itself according to French regulations. Hold on to your hats, this is going to be…mildly interesting to most!

Here are some facts laid bare:

Firstly, there are two different Regulations when it comes to insulation / renovation that should to be adhered to in France: RT 2012 and RT 2007.

The RT 2012 applies to all new builds and extensions that had their Permis de Construire approved after January the 1st 2013.

The RT 2007 applies to all renovated properties i.e. older properties built before 2012.


The RT 2012 has the objective to achieve a Cep<50kw/h/m² in the following domains:

1/Chauffage – Heating

2/L’éclairage – Lighting

3/Eau Chauds -Hot Water

4/Auxiliaires – Ventilation etc.

5/Sanitaire – Sanitation

**Cep stands for consomption d’énergie primaire Basically it’s a measurement of how much (primary) energy your home consumes, which is what is then indicated on your DPE or Diagnostic Report under ‘Logement économe’ when you buy or sell a house. The closer this is to A, the better.

So, this basically means that the consumption of primary energy of a residential building should ideally be 50kw / per hour / per m².

The way this is measured is by using a technique called Blower Door which tests the flow of air in a sealed property.

When building a new house or extension for that matter, there are 2 stages that should be followed:

1/ The Permis de Construire RT 2012 – When this is submitted everything MUST be included as it is impossible to change afterwards!

2/ The Attestation Permis – This is the inspection of the property after its built which verifies that everything on the Permis de Construire has been respected. When you receive this certificate, it means that your house conforms, phew!

Now for the facts of the RT 2007, which applies to most of us Expats who fall in love with the more crumbling older French properties through our rose-coloured specs.

There are 8 points of Thermal Regulations that need to be considered:

1/ Isolation – Insulation

2/ Menuiserie – i.e. windows and doors

3/ Murs – External Walls

4/ Sols- Ground Floors

5/ Ventilation

6/ Production Chaud -Heat productivity i.e. Hot water

7/ Eclairage – Lighting

8/ Chauffage – Heating

Each of these 8 points has an ‘R’ value, which is effectively the desired thermal resistance value i.e. How much heat each of these points should resist or keep inside your home.

Now just to confuse things, there are two types of performance ‘R’ that you can choose to adhere to and these basically depend on whether you want to benefit for the 5.5% TVA or Credit d’Impôt on your factures OR simply be eligible for the 10%TVA surcharge. I will explain the difference in another shorter post!


TVA 10%                                                       TVA 5.5%

Walls – Minimum R = 2,3                   Walls – Min R = 3,7

But how do we calculate the ‘R’ value? I hear you cry, well basically ‘R’ equals: –

The thickness of the insulation chosen divided by The co-efficient Lambda

this funny sign is the symbol used to indicate the thermic conductivity of the insulation  material or ‘Lambda’

Here’s a link where you can calculate it easily online:

NB: Don’t forget that the actual walls themselves have an ‘R’ value so this link is great as you can firstly calculate the ‘R’ which already exists on, say your 12cm thick granite stone wall, then calculate the thickness of the insulate needed thereafter……….Just make sure that the granite walls have been adequately repointed first!

To make it easy though, this ‘R’ value is always marked on the packaging of the insulation material you use and, so you just have to check that the ‘R’ matches the requirements of each of the 8 points listed above. Remember it’s always better to be slightly over than under!

Here’s a table I found online of the required ‘R’ values of a few of the ‘points’ to give you an idea:




Combles Perdu = Roof

Combles aménagés = Ceilings or floorings (of attic space)

Murs = Rampart walls

Planchers = (Ground) Floor

Toiture Terrasse = Roof of outside terrace space



Therefore, to sum up, when choosing your insulation whether it be laine de verre (glass fibres), laine de roche (rockwool), laine de bois (wood fibres), laine de chanvre (hemp fibres), polystyrene floor insulation etc. etc. then the bare minimum to adhere to in terms of the ‘R’ value is indicated in the right column above. However, if you think you are eligible for the 5.5% TVA or credit d’impôt, then the ‘R’ value of your insulation should be as per indicated in the left-hand column, just make sure that you get an RGE registered artisan to install it for you.

If, of course, you don’t give a hoot about adhering to these rules & regs, it really isn’t as though someone’s going to be knocking on your door to punish you, but it may mean that your house is undervalued when you come to sell, because of your under-performing DPE /Diagnostic Report, or that your energy bills are a lot higher than they should be. And if you were to dig a little deeper, the environmental impact of your home may not be in keeping with what the French government envisage to achieve in terms of diminishing the overall energy consumed by the building industry (38% by 2020) – naughty! But then again, what do we care, we only came for the cheese and wine, right!?!

One more thing. The type of insulation you choose for each of the ‘points’ or areas in your home should be certified by ACERMI – but that’s a whole other post!…

There, is that clearer?

P.S. This was as hard for me to write as it was for you to read. Phew!