Op-ed articles

Managing Heat More Efficiently in Homes and Industry

Valérie Mancret-Taylor
Valérie Mancret-TaylorExecutive Director of ANAH

"To achieve the target of reducing these emissions by 75% by 2050, France’s building stock, particularly in the residential sector, will need to undergo a massive retrofit."

Home Retrofitting, a Social and Environmental Issue

In France, the building sector (homes, offices, etc.) accounts for 24% of greenhouse gas emissions and 44% of final energy consumption. To achieve the target of reducing these emissions by 75% by 2050, France’s building stock, particularly in the residential sector, will need to undergo a massive retrofit. In this article, Valérie Mancret-Taylor, Executive Director of French housing improvement agency ANAH1, discusses the dual challenge facing energy retrofitting – fighting climate change and alleviating social hardship.

Around 65% of all French dwellings (close to 35 million) were built before 1975, the year when thermal regulations were introduced. Prior to that, and especially between the late 50s and the mid-70s, building energy performance was very erratic. Today, roughly seven million homes are considered to be “leaky”.

Energy Retrofit vs. Energy-IntensiveDescribes a building, mode of transportation or industrial process that uses large amounts of energy.

The energy retrofit process concerns a wide variety of dwellings. First, it’s necessary to distinguish between individual housing (20 million units) and collective housing (15 million units). In a house, every facade is exposed, which isn’t true for a unit in an apartment building. The dwelling’s location – city center, suburbs, rural area, surrounding region – introduces other variables into the equation.

But a key determinant of the process is the homeowner’s social and economic conditions. Around one-third of the seven million “leaky dwellings” in the country are occupied by low or very low-income households which may, as a result, be living in fuel poverty. Either their home wasn’t well insulated when it was built, or it has deteriorated due to a lack of maintenance. In either case, the result is the same: the occupants often spend more than 10% of their income to heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... their home, which is the threshold for defining fuelFuel is any solid, liquid or gaseous substance or material that can be combined with an oxidant... poverty. For these people, a retrofit could help lower their heating bill and increase their purchasing powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... , but the decision to invest in an energy renovation project is a difficult one to make.

In collective private ownership, it can also happen that co-owners have difficulty agreeing to upgrade common areas, like the boiler room, for example. The condominiums (which are often financially distressed) may be inhabited by older people who are reluctant to vote for a refurbishment several years down the line or first-time buyers who are still struggling to pay their mortgage. In this situation, strong financial solutions and a lot of careful explaining will be necessary to convince the co-owners to approve an energy retrofit. There is also the case of private owners who lease their property at a low rent and don’t have enough money to make a capital investment.

Combating Fuel Poverty and Climate Change

ANAH offers advice, support and financial assistance to these different types of private homeowners, either directly or by subsidizing housing enhancement initiatives carried out by the local authorities. The agency is committed to other issues as well, not just fighting fuel poverty, even if it’s best known for its “Habiter Mieux” (Live Better) program. ANAH also addresses the problem of substandard housing and the need to adapt homes to make them safe and comfortable for the elderly and disabled.

But the fight against fuel poverty is all the more urgent, due to the fact that poorly insulated buildings are often equipped with inefficient heating systems that emit significant amounts of greenhouse gases. Helping a family overcome fuel poverty is as much a climate issue as it is a social one.

That’s why – for social and environmental reasons – homes built prior to 1975 need to be renovated. The “end of the month, end of the world, same struggle” slogan, which recently emerged during the street protests, rings true in the housing sector.

The number of private, low-energy efficiency homes occupied by low-income families is estimated at between 1.5 million to 2 million units. The government’s objective for ANAH is to implement 120,000 upgrade projects per year, including 75,000 energy retrofits. We’re getting close to the mark. In 2017, ANAH helped refurbish 81,000 dwellings, 52,000 of which were energy retrofits. In 2018, we carried out 94,000 upgrades, including 62,000 retrofits. When the agency launched its “Habiter Mieux” program in 2011, there were 6,600 beneficiaries; now there are ten times more. And since then, we have provided support to a total of 305,000 households. The snowball effect is definitely real, even if it’s hard to get it going. In the private housing sector, you’re not dealing with professionals like real estate developers or social housing associations, but with ordinary people. As a result, you need to spend time explaining things and helping them choose the refurbishing project that’s right for them, all within a regulatory framework that will remain stable over the long term.

Our program is part of the building energy upgrade plan launched by the government in 2017 for a period of five years. It concerns both public and private housing and offers additional incentives to homeowners to insulate their homes or replace their boiler. The plan calls for 380,000 private homes and 120,000 public housing units to be upgraded annually beginning in 2017.


Valérie Mancret-Taylor has been the Executive Director of French housing improvement agency ANAH since 2018. Created in 1971, the agency is a public institution placed under the authority of the Ministry of Territorial Cohesion and Relations with Local Authorities, the Ministry of Public Action and Accounts and the Ministry of Economy and Finance. Its mission is to fight social and territorial inequality by improving the existing stock of private homes. The agency’s “Habiter Mieux” program provides a suite of support measures organized under three labels: Serenity, Agility and Co-ownership.

(1) See the ANAH website (in French) – https://www.anah.fr/


Christophe Debard
Christophe DebardExecutif Chairman of ALLICE

"Minimizing heat loss and maximizing heat recovery are two key requirements for improving industrial energy efficiency and ensuring the transition to a green economy. "

Reducing Industrial Waste Heat

HeatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... is an energy carrierA synonym of secondary energy (see definition). that spans the full spectrum of collective and individual human activity, from farming and industry to housing and transportation. Minimizing heat loss and maximizing heat recovery are two key requirements for improving industrial energy efficiency and ensuring the transition to a green economy. In this article, Christophe Debard, Executive Chairman of Alliance Industrielle pour la Compétitivité et l’Efficacité Énergétique (ALLICE), an initiative focused on energy efficiencyIn economic terms, energy efficiency refers to the efforts made to reduce the energy consumption of a system... and innovation, discusses the issue of industrial heat recovery and reuse.

Heat energy accounts for the biggest share of industrial energy consumption, well ahead of electrical energy. That’s because industry uses heat for a wide variety of processes, including combining and separating elements and making polymers and plastics, not to mention drying, cooking, welding, sterilizing, washing, heating, and even cooling. Heat energy is obtained mostly by burning gas, fuelFuel is any solid, liquid or gaseous substance or material that can be combined with an oxidant... oil and coalCoal is ranked by its degree of transformation or maturity, increasing in carbon content from... , but it can also be produced from electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... .

Not surprisingly, the biggest consumers of heat are heavy industry sectors like steel, metal, chemicals/petrochemicals and building materials (bricks, cement, glass wool, etc.). Heat demand is also high in the textiles, plastics, rubber and food processing sectors. The agri-food industry comprises a significant number of small and medium-sized operations, all of which are very heat-intensive, from canneries and cookie factories to dairies and slaughterhouses. Textile finishing plants and paper mills consume large amounts of heat as well, but their number has declined in France.

Approximately 100 terawatt-hours (TWh) of the total heat used by French industry (estimated at nearly 300 TWh) is lost. This is referred to as waste heatLike waste energy, waste heat is heat whose release during a process or the manufacture of a product is unavoidable... . The waste heat is released to the cooling water circuit, eventually winding up in a river, or to the atmosphere, where it dissipates. Waste heat recovery is therefore an important precondition for efficient energy management.

Industrial Waste Heat Sources

The biggest waste heat source (roughly 30% of the total) is steam, which is produced in great quantities by industrial drying.

Almost an equivalent amount of waste heat is generated by cooling systems, such as those used in the production of injected molded plastics. Furnaces for heat treating steel and metal account for about 20% of waste heat, and boilers and boiler rooms 15%.

Efficiency improvements aimed at reducing heat loss have been most prevalent in the boiler sector. This is due to the fact that boilers can be serially produced according to pre-established standards. Refrigeration condensers for keeping systems cool can also be mass produced, which makes implementing improvements easier. On the other hand, many industrial processes require specific built-to-suit solutions. For example, the requirements for a furnace that releases acid fumes and one that is full of dust generated during grain processing are different.

Waste Heat Recovery

Another way to reduce waste heat is to reuse it.

  • At temperatures above 100°C, waste heat can be recovered fairly easily. Below that, it’s more difficult. When heat is transferred in a heat exchanger, for example, there is always a temperature difference between the primary and secondary circuit. The point where the smallest temperature difference occurs is called the pinch point.

About half of the 100 TWh of waste heat produced has a temperature of over 100°C. The easiest thing to do is to reuse the heat within the same process or at the same site. If the waste heat is in the form of steam, it can also be converted into electricity.

  • For the other half of waste heat with a temperature below 100°C, the applications are more limited. In the agri-food industry, low-grade waste heat can be used for heating wash water. To make waste heat more useful, its temperature can be increased using heat pumps and other complex technologies.

But the economics need to be considered. The installation of a heat recovery system is an investment that entails maintenance costs. Any such solution therefore needs to be examined in terms of overall energy cost. Another option would be to adopt an industrial symbiosis approach, which would involve sharing heat with another company in an eco-industrial park or supplying heat to a district heating system. But that would create contractual obligations. What would happen if the plant supplying the heat were to be relocated?

Thermal management is often linked to “aeraulic” performance (the study of airflow/gas flows, as opposed to hydraulics, which deals with the conveyance of liquids). Ventilation and filtration are often important components of indoor heat management systems. A data center is a typical example, where air needs to circulate to dissipate heat generated by the servers, while maintaining a constant temperature.


Christophe Debard is Executive Chairman of Alliance Industrielle pour la Compétitivité et l'Efficacité Energétique (ALLICE). A nationwide body comprised of companies and experts that was founded in 2018, ALLICE is committed to improving the energy efficiency of French industry and supporting innovative developments in this field. Christophe Debard is a mechanical engineer who worked at Institut Français du Textile prior to joining Centre Technique des Industries Aérauliques et Thermiques (CETIAT), a research laboratory dedicated to the study of airflow, heat and acoustics, where he continues to serve as Sales and Marketing Director.

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