Heating and air conditioning
© Gritt Zheng, Unsplash.

Heating and air conditioning

  • Energy and buildings
  • Construction and renovation
  • Temperature

The adoption of more energy-efficient heating and cooling practices has become a priority in order to reduce the energy consumption of buildings. Temperature control, thermal insulation, natural ventilation and other passive energy saving measures are always to be preferred over energy consuming technologies. More energy-efficient appliances can also contribute to lowering the energy bill, as can their positioning and maintenance.

Why is this important?

Energy production is responsible for 42.5% of global CO2 emissions. (1) Heating and cooling systems are responsible for 50-60% of the energy bill of hospitals and offices. (2) Energy demand for air conditioning tripled between 1990 and 2016, reaching 8.7% of total global energy demand, and it could triple again by 2050. The refrigerants contained in air conditioning equipment also contribute to global warming because of their high global warming power, between 1,300 and 3,260 times higher than CO2 for HFCs. (3)

Reducing the energy consumption of buildings means reducing their carbon footprint.

What is the solution?

Energy consumption of buildings is mainly related to heating and cooling, which are directly linked to several factors such as the desired temperature, the volume of air heated or cooled, the number of hours and the humidity of the air. By acting on these factors and adopting more sober practices, it is possible to significantly reduce energy consumption and carbon footprint of buildings.

The most ecological energy is the one that is not consumed. Adjusting the interior temperature of a building by a few degrees has a significant impact on the energy bill. Fans, plaids, curtains, carpets or blinds, common sense measures must accompany these changes.

Thermal insulation, natural ventilation or solar protection, passive energy saving measures should always be preferred to energy consuming technologies.

Choices, smart positioning, and good maintenance of heating or air-conditioning equipment also allow to reduce the energy consumed, because of a greater efficiency of the devices.

Key facts


Lowering the heating temperature by 1°C can result in 7% energy savings. (4)


Setting an air conditioner 1°C higher can reduce the amount of electricity used by up to 10%. (5)


Fans use 100 times less energy than air conditioners. (6)


Poorly insulated hot water pipes can result in energy losses of 30-40%. (7)


Heating and cooling account for 50- 60% of energy consumption in hospitals and offices. (8)

Key actions

Heating and air conditioning
© Will/Unsplash.

To consider

  • Potential co-benefits

    • Reduced energy bills
    • Less pressure on the electricity grid and reduced global risk of power cuts
  • Success conditions

    • Support from building occupants
    • Installations carried out by competent professionals
  • Prerequisites and specificities

    • Where possible, establish a complete thermal diagnosis of the building, to prioritise, specify and reliably cost the expected results of the most suitable technical solutions
    • There is no single solution, the measures must be chosen according to the situation
  • Potential risks

    • Excessive temperature reduction in winter or setting the temperature too high in summer can have negative consequences on the occupants health, their motivation, well-being and efficiency

Point of attention

  • Point of attention

    The temperature in health centres or hospitals has a direct effect on the well-being and recovery of patients. According to a study by BMC Public Health, the installation of heating, ventilation or air conditioning improves the recovery of patients and increases the effectiveness of treatments. (16)

Success stories

The Tunisian population asked to air-condition less and better

Fearing an energy shortage during 2017 and 2018 summers, the Tunisian Electricity and Gas Company (STEG) has asked the population to take measures and to pay particular attention to air conditioning. Air conditioning alone accounts for nearly 50% of national electricity consumption in Tunisia, and the number of air conditioners almost quadrupled between 2009 and 2013, from 400,000 to nearly 1.5 million units. “We are going to make consumers aware of the need to ensure, when purchasing an air conditioner, that it corresponds perfectly to their real needs, and that it does not consume energy, by consulting the energy label. Consumers should also set the air conditioner to 26°C, since each degree lower than this results in 6 to 12% more energy consumption. They should also avoid opening doors and windows when the air conditioner is on.  He should only turn on the air conditioners in places where it is strictly necessary.” (17)(18)

Emission-free cooling: wind sensor in Iran

The Iranian city of Yazd is home to a system of ancient engineering marvels that includes an underground refrigeration structure called a yakhchāl and an underground irrigation system called qanats. Among Yazd’s ancient technologies is the wind sensor, or bâdgir in Persian. These remarkable structures can often be seen above the roofs of Yazd. They are often rectangular towers, but can also be found in circular, square, octagonal and other ornamental shapes. Air entering the structure is pushed down due to the change in buoyancy of the air with temperature – warmer air tends to rise above the colder, denser air. This channels cooler outside air to the building below. Sand or debris settles at the bottom of the tower. The warm indoor air rises and leaves the building through another tower or opening, helped by the pressure inside the building. (19)

Sea Water Air Conditioning, the University Hospital of La Reunion Island is a pioneer

The University Hospital of La Reunion Island will be installing the innovative SWAC (Sea Water Air Conditioning) technology in Saint-Pierre. This project is unique in the world in terms of its size and environmental benefits, with a substantial reduction in electricity consumption of up to 90%, i.e. 10 GWh per year, the equivalent of the consumption of a town of 6,000 inhabitants, and savings on cooling management costs of at least 10%. The technology consists of pumping cold water from great depths (around 5 degrees at 1000m) and transferring the cold contained in this water to the hospital’s air conditioning network by means of a heat exchanger. The seawater that comes out of the heat exchanger (at about 12°C) is then returned to the ocean at a depth appropriate to its temperature and without impact on its environment. Commissioning is scheduled for 2023, for a contractual period of 20 years. The investment represents an amount of €45 million, co-financed by the European Regional Development Fund (ERDF) and the French Agency for Ecological Transition (Ademe). (20)

Raising awareness and changing practices at the Cannes hospital

The Cannes hospital system allows a maximum difference of 6°C between indoor and outdoor temperatures. Radiators have been removed in technical corridors where doors are often open. Presence and movement detectors regulate lighting. A software program monitors consumption and alerts in case of over-consumption. Energy-intensive water fountains have been removed; staff are now consuming tap water. An awareness-raising process has been undertaken with staff using posters in the premises and information in the internal newspaper, for example about temperature settings in each room. The energy bill fell by 10% in 2015. (21)

Energy management plan at the Lille Hospital Center

In November 2022, the Lille University Hospital deployed an extensive energy management plan to rapidly reduce its energy consumption while ensuring that it would not affect the quality of care provided. The heating set point has been reduced to 19°C from 20°C, and in the rooms to 21°C from 22°C. The doors of the care access services described as “energy sinks”, will eventually be equipped with automatic closing systems. According to the Director, “these measures should enable us to reduce our consumption by at least 7%, which means 2 million euros less on the bill, the equivalent of the consumption of 600 families in less than a year. ” This approach is not new, since between 2011 and 2021, the hospital has managed to reduce its gas bills by 15% and its electricity bills by 14%, while its activity has continued to increase. The air conditioning system, for example, was replaced by much more efficient and energy-efficient cooling units. (22)(23)

Swiss cantonal authorities turn down the heat

During 2022-2023 winter, office temperatures in the State of Fribourg was limited to 19°C and hot water was cut off, unless necessary. Staff were forbidden to compensate with private heating. The canton of Berne opted for a temperature of 20 °C in offices and common rooms, 17 °C in multipurpose rooms and workshops, 13 °C in empty buildings and rooms, and 7 °C in warehouses and garages. The temperature in hospitals and care homes was set at 23 °C in the canton of Geneva. In the canton of Valais, it was requested to set boilers temperature in public buildings between 50 °C and 55 °C. Similar recommendations were made to municipalities and private companies. (24)

Replacing air conditioners and boilers in Geneva with hydrothermal energy

Conducted since 2009 in the canton of Geneva, the GeniLac project aims to replace air conditioners as well as oil and gas boilers with hydrothermal energy. GeniLac is part of the canton’s climate strategy and is being implemented by the Services industriels de Genève (SIG). Water from the lake is used to heat and cool buildings. “This resource represents an almost inexhaustible and local energy reservoir. The water is drawn from a depth of 45 meters and is at a constant temperature all year round. It passes through mechanical exchangers to be used directly to cool the buildings in summer. In winter, this water is used to produce hot water thanks to the heat pumps, which run on 100% renewable electricity, which considerably reduces CO2 emissions. » (25)

Brittany cider mill replaces its cooling system with ammonia technology

The Cidrerie de Domagné in Brittany changed its cooling system by replacing its eleven compressors with an ammonia-based technology. This action allows both to anticipate the ban on certain refrigerant gases by 2030 and to reduce the energy bill. By combining its impact with the efforts made elsewhere, particularly in heat recovery, Domagné has reduced its gas and electricity bills by 7% over five years, saving 530 tons of carbon equivalent or 550 return flights between Paris and New York each year. (26)

Tools and good practices

  • CEREMA guide: simple and concrete actions for the management of real estate assets

    This book offers managers of tertiary buildings simple, economical solutions that require little work to improve and optimise energy and budgetary expenses in buildings, while ensuring their quality of use. Lighting, heating, ventilation... all energy-consuming items are covered (in French)

    Read here
  • Advice sheets on energy performance in offices, ADEME

    This website contains solution sheets, advice for action, key figures, tools and resources on lighting, ventilation and air conditioning, heating, electrical equipment, and buildings (in French)

    Read here
  • Air conditioning energy efficiency in tropical regions, the Francophone Institute of Energy and the Environment

    Volume I, entitled Design of New Buildings, is devoted to heat balances assessment, overall operating costs of the building, and sizing and selection of an air conditioning system. Volume II, which deals with the operation of existing installations, presents different measures that can be carried out to improve energy efficiency of buildings. It describes the traditional technical approach, while introducing the innovative concept of energy performance contracting in building maintenance (in French)

    Read here
  • Renovation plan for the cold production of the hospital of Tourcoing

    This plan presents in detail the objectives, design and project management elements, heat recovery and energy gains. One of the main objectives of this large-scale project being to reduce the energy consumption of the buildings (in French)

    Read here
  • Hospital acts for the planet, Guide to good sustainable development practice for health and care facilities, 2015 (in French)
  • Sizing tool for solar air conditioners, ARUP

To go further

  • Heating and air conditioning: challenges and opportunities in France, Europe and the world

    The increasing number of cold snaps and heat waves, as well as the long life of poorly performing buildings already built, already foreshadow the many challenges ahead. Reducing CO2 emissions, improving thermal comfort and maintaining the stability of the electrical grid are all challenges to be met. Given the current technology mix and the magnitude of future heating and cooling needs, the potential for improving energy efficiency and reducing CO2 emissions is substantial (in French)

    Read here
  • Passive systems for energy saving in buildings in tropical climate

    A model building was designed, meeting the requirements of a tropical climate. An energy simulation was performed to compare the thermal behaviour and thermal comfort conditions of the model building under different cases of passive systems: thermal mass, solar shading, cross ventilation, and dehumidification.

    Read here


(1) International Energy Agency, Energy saving actions by EU citizens could save enough oil to fill 120 super tankers and enough natural gas to heat 20 million homes, 2022. Read here.

(2) Hohne, P.A., Kusakana, K., and Numbi, B.P., Improving Energy Efficiency of Thermal Processes in Healthcare Institutions: A Review on the Latest Sustainable Energy Management Strategies, 2020. Read here.

(3) Climate and Clean Air Coalition, Hydrofluorocarbons (HFCs). Read here.

(4) ADEME, Lowering the heating set point temperature. In French. Read here.

(5) International Energy Agency, Energy saving actions by EU citizens could save enough oil to fill 120 super tankers and enough natural gas to heat 20 million homes, 2022. Read here.

(6) Coolingfanreview, Air conditioner vs fan electricity usage, 2023. Read here.

(7) ADEME, Heating. In French. Read here.

(8) Hohne, P.A., Kusakana, K., and Numbi, B.P., Improving Energy Efficiency of Thermal Processes in Healthcare Institutions: A Review on the Latest Sustainable Energy Management Strategies, 2020. Read here.

(9) Tham, S. et al., Indoor temperature and health: a global systematic review, 2020. Read here.

(10) ADEME, Reduce your heating bill with a programmable thermostat, 2020. In French. Read here.

(11) French Ministry of Energy Transition, Solar, 2023. In French. Read here. 

(12) ADEME, Heat pumps, 2022. In French. Read here.

(13) IZI by EDF, How to choose an inertia radiator?, 2022. In French. Read here.

(14) Reseau Chu, Seawater air-conditioning, The Reunions University Hospital is a pioneer, 2019. In French. Read here.

(15) Xpair, 20 facts to optimise heating and cooling, 2020. In French. Read here

(16) Lenzer, B. et al., Health effects of heating, ventilation and air conditioning on hospital patients: a scoping review, 2020. Read here.

(17) Afrik 21, Tunisa: STEG is launching an energy efficiency program for this summer… Hot!, 2018. In French. Read here.

(18) FranceInfo, Air conditioning: Tunisia at the limit of its electricity consumption, 2017. In French. Read here.

(19) BBC News Africa, The ancient Persian way to stay cool, 2021. In French. Read here.

(20) Reseau Chu, Seawater air-conditioning, The Reunions University Hospital is a pioneer, 2019. In French. Read here.

(21) Comité pour le développement durable en santé, The hospital acts for the planet: Guide to good sustainable development practice for health and care facilities, 2015. In French. Read here.

(22) Comité pour le développement durable en santé, The hospital acts for the planet: Guide to good sustainable development practice for health and care facilities, 2015. In French. Read here.

(23) Lille Actu, Lower heating, LED lamps… The measures of the Lille University Hospital to save energy, 2022. In French. Read here.

(24) Le Matin Switzerland, The cantons lower the heating and turn off the lights, 2022. In French. Read here.

(25) Genie, Genilac: a major, sustainable energy innovation for Geneva, 2016. In French. Read here.

(26) Les Echos, 7 companies at the forefront of energy sobriety, 2022. In French. Read here.


Cover photo © Gritt Zheng/Unsplash.