Is it better to lower the consumption of buildings… or increase their production of renewable energy?

The two approaches are complementary; it is not appropriate to oppose one to the other. We will need both to make our energy transition a success.

Our building stock is an energy chasm. By retrofitting our buildings, we should be able to save nearly 36 TWh of final energy, including 12 TWh of electricity [→ Q29]. A residential or administrative building of average performance today consumes 250 kWh of primary energy per m2 of inhabited area, of which about 150 kWh/m2 is for heating and the balance for other needs (lighting, appliances, technical installations). It would consume less than 100 kWh/m2 if it were renovated to the Minergie® standard, i.e. had a 60% reduction in primary energy consumption (150 kWh/m2).

It is important to realise that each kWh of renewable energy used to heat a poorly insulated building will not be available for other applications. If the potential of renewable energy were unlimited, this would not be a problem. However, this is not the case. On the contrary, the possible contribution of renewable energies to Switzerland’s energy supply is limited, especially in winter, precisely when our heating needs peak. These resources must therefore be used wisely. In other words, buildings must first be made more energy-efficient (e.g. insulated to reduce heating requirements in winter, heat protection to prevent air-conditioning in summer, improved natural and artificial lighting, increased efficiency of technical installations, etc.) before they can be supplied with renewable energies. Otherwise, Switzerland will inexorably increase its dependence on energy imports.

In addition, investments to improve the energy efficiency of buildings are often more cost-effective than those required to exploit renewable energies. For example, solutions that allow a building to be well insulated to reduce its heating needs or improve the efficiency of the boiler room generally offer better returns on investment than options for heating from renewable sources. An exception is the solar water heater. If properly sized and used, it provides hot water at a price that is often lower than other methods of production.

Of course, this does not apply to buildings whose energy performance is already very high thanks to very good insulation. Indeed, the better a building is insulated, the more expensive it will be to improve it further, as it will require the use of high-performance - and therefore very expensive - construction techniques and insulating materials. Thus, from a certain level of insulation quality, the returns on these investments become diminishing. It is then more interesting to cover the residual energy demand by providing renewable energy.

Conclusion: for all buildings that do not meet high insulation standards, retrofitting (insulation) saves valuable renewable resources and often makes economic sense. They should therefore be given priority over measures to increase the production of renewable energy, especially as they often improve comfort.


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