Emissions from the real estate sector are caused by:
- - the construction of the building
extraction of raw materials, production, processing and transport of materials, installation...
- - its operation
heating, cooling, electricity, maintenance, etc.
- - and its dismantling at the end of its life
demolition, transport of waste to landfill, incineration, recycling...
However, at present in Switzerland, only the emissions linked to the operation of the building are regulated. Indeed, cantonal energy laws set, for example, a minimum supply of renewable energy, prohibit certain types of heating (including electric), and make certain measures mandatory, such as an energy audit when selling a property3.
Construction and demolition, on the other hand, are not subject to any particular regulation with regard to CO2 emissions and are therefore only subject to market laws. When you consider that a solar panel produced in China costs much less than one produced in Switzerland, it is easy to imagine that the grey energy of the building is sky-high.
However, in a new energy-efficient building, more than 70% of greenhouse gas emissions occur during construction4.
Of course, building has other indirect effects, also leading to global warming, which are less easy to measure.
These include soil sealing, heat islands, loss of biodiversity, depletion of natural resources and waste generation. The construction sector generates 84% of the waste in Switzerland5! And construction also means destruction. This includes the destruction of biodiversity, carbon sinks and agricultural land.
Fields of action
So how can we drastically reduce building-related emissions? A first answer to this question could be simply not to build ;) As with any responsible decision, the first question to ask is: Does it meet a real need? What are the alternatives? Can we do more with less?
Carl Elefante, the former president of the American Institute of Architects, also said that "the greenest building is the one that already exists"6. Indeed, renovating existing buildings - especially in terms of energy efficiency - and extending their lifespan rather than destroying and rebuilding them, would considerably reduce the emissions associated with the production of new materials. But here again, market laws work against such strategies. While changing building zones to allow densification in cities is laudable to avoid urban sprawl, it also leads many investors to raze buildings long before they reach the end of their life to build new - bigger, taller - buildings to maximise profit.
When planning a renovation or a new construction, we can - and should? - use the following levers:
- - design
shape and orientation of the building, footprint and surface area per person, potential for future transformation and dismountability, efficiency of the supporting structure...
- - choice of materials
bio-based materials, reuse, local resources, etc.
- - technical systems
low-tech systems, low energy consumption, passive systems, etc.
- - and lifestyles.
Because even in the world's most ecological building, heating to 25°C while opening windows in the middle of winter, it will have brought us nowhere.