Energy efficiency of buildings: practice far from theoretical expectations

Quelles sont les technologies qui permettront de réduire les émissions de gaz à effet de serre à moindre coût ? En réponse à cette question, l'entreprise de conseil McKinsey a publié en 2007 un graphique qui représente une estimation pour 2030 du coût de la tonne de CO2 évitée en mettant à exécution diverses stratégies de réduction des émissions.

The technology that comes out winning in this classification is the insulation of buildings, with a negative cost, that is to say a gain greater than 150 euros per tonne of CO2 avoided!In other words, it is a “winning winning” solution which should make it possible to reduce CO2 emissions while being profitable economically: the cost of the insulation would be largely offset by future savings on the energy bill.

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Consistent with these calculations, in many countries the public authorities have implemented policies to promote the isolation of old buildings.With all the same a paradox: if isolate is so economically advantageous, it is in the interest of the occupants (households, traders, industrialists) to embark on energy renovation work without subsidy, unless they are tenants or thatTheir bank refuses to make them a credit, in which case a loan guaranteed by the State should lift the financial lock.Given the forecasts of McKinsey experts, economic rationality should therefore be enough to push the owners to isolate their housing, especially with these financial aids which are all inbat effects.This is not what we have seen, especially in the United States.

Paperwork and dust

The American federal government has set up an aid program for the most disadvantaged which fully supports the energy renovation of their accommodation.Poor households can have work carried out of 5.000 dollars without paying anything from their pocket.A study carried out in 2015 tried to understand why a very small number of eligible households participate in this generous program.Is it for lack of information?By aversion to administrative procedures?Researchers randomly selected 30.000 eligible households from Michigan, half of which benefited from a promotion campaign: letters and telephone calls to publicize the program and logistics support to set up an application file.This relatively expensive campaign (450.000 dollars) has increased the participation rate, but the increase remains low.If we compare households who benefited from the promotion campaign with the others, the program application rate goes from 2% to only 15%.In the end, 6% of those who received support to participate in the program performs work against 1% for the others.The rate of carrying out the work conditionally to the submission of an application file is not higher for those who have benefited from the promotion program.The authors of this study conclude that information and transaction costs are not the main brakes on energy renovation.The low enthusiasm for this type of program can only be explained by non-monetary costs, such as the noise and dust caused by renovation work.

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Energy renovation not always profitable

Various studies have estimated the energy savings carried out to compare them with those provided in energy renovation programs.They all show that we are far from the account.The fraction of the savings made compared to those which had been announced varies from 30% to 58% depending on the study.In the end, if we compare the cost of renovation with energy savings, the investment is not always profitable, contrary to what was advanced by McKinsey.In the 30 sample.000 households in Michigan, the annual profitability rate is estimated at −7.8% which bears the cost of the ton of CO2 avoided at 200 dollars, and therefore retrograde the insulation of buildings in the last position of decarbornation solutions such as estimated by McKinsey.In France, a study by the conversation on survey data leads to the same conclusion of negative yield of energy renovation.With 1.000 euros in work, we obtain an average reduction in the bill of 8.4 euros per year.To recover the initial investment, we must therefore wait...120 years!

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This discrepancy between the expected savings and the savings made, known as "Energy Efficiency Gap", is partly explained by too optimistic assumptions of the simulation models used by building engineers.but it is not the only reason.By breaking down all the insulation measures of the walls, ceilings and windows, an American study of 2020 estimates that projection errors explain 41% of the lag.The rest is largely due to heterogeneity in the quality of the work carried out: the authors estimate that the gap between the energy savings planned and carried out would be reduced by 43% if all the work was carried out by the 5% best companiesrenovation.

Information asymmetries on the renovation market

Even if thermal insulation is a simple and mature technology, its performance is very variable.It is dependent on many factors such as the type of building, the materials used, the heating system, the thermal bridges, the climate, the skills and the involvement of the technicians in charge of the site.A whole range of insulation and insulation techniques are available on the market.Not easy to make your choice when you are not an expert.

Unless you carry out the work yourself, the energy efficiency of our accommodation is left in the hands of one or more professionals who are supposed to do at best at lower cost.This creates a problem of moral hazard highlighted in an article published in 2018.The owner who does not have the expertise to ensure the quality of the work, the temptation is strong for the craftsman to shy the site with entry -level equipment.Regardless of the energy savings made, it will be paid by the owner (and the State via the grant).If it turns out that the expected energy savings do not come true and do not lower the invoice, it will be too late to ask for accounts.The authors document the existence of this moral hazard.They show that energy efficiency is less for work whose quality is more difficult to observe, such as insulation of attic and when they are made on Friday rather than other days of the week.

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This moral hazard is coupled with an anti-selection problem because it is difficult for an owner to assess the competence and honesty of renovation professionals.Competition in the presence of anti-selection draws quality down by a so-called "market for lemons" mechanism.Customers do not have the skills to distinguish good professionals from bad ones, only those who manage to lower costs survive by cutting up on quality.Consequently, competence and performance are not sufficiently remunerated.In the end, the owners renounce investing, or does it for small work partly subsidized by taxpayers.

A sector that deserves to be better regulated

The energy renovation of buildings is one of the options of the economy decarbonation.If it is true that it is socially desirable, it is not profitable for owners without subsidies as long as energy is cheap.Financial aid does not do everything.The State must also better regulate the energy renovation sector and professionals in the sector must better discipline themselves to ensure that promises of energy savings are materialized.

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