On housing insulation – Part 1/2

hlm.jpgFollowing to a comment by my friend Etienne in this article, I will take the most interesting findings of my Master’s Thesis to exemplify how insulating a place is definitively worth the money.

My thesis for the Audencia Nantes Management School tackled the issues of energy scarcity and climate change in relation with the French housing sector.

I paid attention to renewables, nuclear energy and of course energy performance. The latter is indeed the subject of today’s post.

To begin with, one needs to know that the housing sector is the biggest primary energy consuming item in France with 45.8 percent of the total energy consumed. It is also emitting a quarter of the carbon dioxide, the main greenhouse gas. Hence the importance of cutting the energy needs there, we will see that it can be done quite easily.

For the sake of the argument, and last year for my thesis, I used a case study done by the “Isolons la terre” association of companies. Below are the most interesting findings.

This handles the case of a 80 year-old house that had no insulation at all ; wooden windows with simple glazing dating from the construction of the building ; no mechanical ventilation. The place was heated by a natural gas individual heating, it had a derelict electrical water heater and an old electrical installation.

All these factors were resulting of an annual consumption of 350 kW·h/year/square meter of primary energy for heating.

The insulation and renovation has been done with largely available materials that are in the meantime very performing. Among these materials we can note that the external walls were insulated with 10 cm of fibreglass. This divided by a factor four the losses of heat by the walls and it improved as well the soundproofing.

The old windows were replaced by PVC windows with reinforced 4/16/4 double-glazing with argon. The losses of heat due to the windows have been decreased by 75 percent. A more efficient natural gas-fired heating system was also installed.

After renovation, the heating requires 70 kW·h/year/square meter of primary energy. It means that now to heat a similar place with better insulation – and hence energy conservation – five times less energy is required to do the same thing. The cost of such an operation were of 137 € per square meter, without counting taxes. Out of which:

  • 5 € per square meter for insulation of walls
  • 7 € per square meter for ceiling insulation
  • 66 € per square meter heating system
  • 59 € per square meter for the windows

So indeed, Etienne is quite right when he states that not everybody can afford this. But, according to the ADEME, the payback period a such an investment is of eight years with the current prices of energy.

As these prices are mathematically due to increase as times goes and has these materials have a life period of roughly 35 years or even more, we can see the money spent is well spent.

You might say ” Hey, almost no house in France or anywhere in the civilised world is that bad insulated “. I don’t know for other countries, but in France, it is estimated that around 19 million housings have insufficient energy conservation.

According to the INSEE, the national statistics agency :


According to the ” Livre blanc des énergies ” (White Book on Energy) written by the French Ministry of Industry and Energy, a better insulation of all the housings with insufficient insulation could save up to the equivalent of 200 TW-h of electricity equivalent per annum, knowing that the total electricity consumption in France is of 473 TW-h per annum.

200 TW-h, what is that ? 200 Tera Watts per hour, or if you prefer figures : 200,000,000,000,000 watts per hour. Yes, this is indeed a lot of energy.

Soon, I will write the second part of this article with how the French government helps households insulating their housings and related issues.

Edit : direct access to the second part of this article


Edouard is a sustainability and energy professional committed to bringing our societies to a carbon neutral future. He has been writing on related topics on this very blog since 2007.

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12 Responses

  1. Qat says:

    Article très, très intéressant, qui confirme une fois de plus qu’il n’y a pas de maisons trop isolées ( mais seulement des maisons mal ventilées). Si tu le permets, je souhaiterais le mentionner sur mon site, et en traduire quelques extraits, dès que j’aurai un peu le temps..

  2. Edouard says:

    hello Qat !

    Merci pour ton commentaire… 😀

    Ayant mis un lien vers cet article en commentaire à un de tes très intéressants articles, il n’y a pas de problème à ce que tu le mentionnes, à condition bien sur de mettre mon nom et celui du site.

    Quant à la traduction, si tu n’avais pas le temps, je peux faire une version française de cet article avec les points qui t’intéressent. Car moi, malheureusement, j’ai du temps libre ( je préfèrerais nettement travailler… )

    Sinon, cet article est en deux parties, la suivante se trouvant ici. J’y explore les différents avantages qu’une politique massive d’isolation des logements aurait pour la France, je pense que des résultats similaires auraient lieu en Belgique ou ailleurs…

    A bientot !

  3. Meryn Stol says:

    “200 TW-h, what is that ? 200 Tera Watts per hour, or if you prefer figures : 200,000,000,000,000 watts per hour. Yes, this is indeed a lot of energy.”

    That is not true. A watt is a unit of power, or the speed of the energy “flow”. To know the actual “distance” traveled, or the energy consumed, you need to multiply this with a unit of time. Then you get an amount of energy (just like speed is related to distance via time).

    W = P * t;
    d = v * t;

    TWh is most commonly expressed in relation to something else, like per year. You could also have a battery with a few kWh of energy storage. Or a tank full of gas with so much energy in it. Battery capacity is most often expressed as Ampere-hours though. You must multiply that with the battery voltage to get the actual watt-hours.

    See http://www.camerahacker.com/Definitions/Battery_Capacity_Conversion.shtml for example.

    The 473TWh electricity consumption per year in your case comes down to 473 / (365*24) = 53 GW of continuous power. Obviously, more capacity is needed because the load is not continuous.

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