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The concentration of greenhouse gases in the atmosphere has increased sharply in recent decades. As a result, long-wave heat radiation can no longer escape into space unimpeded. Temperatures on Earth are rising as a result. Greenhouse gas emissions (GHG emissions) need to be drastically reduced in order to stop or at least slow global warming.
In the Paris Agreement of 2015, almost 200 countries agreed to limit global warming to well below 2 °C above pre-industrial levels. With this target in mind, Switzerland aims to achieve net zero by 2050. This means emitting no more greenhouse gases than are removed from the air by natural or technical measures. As not all GHG emissions can be avoided, net zero requires not only a reduction in emissions but also ‘negative emission technologies’ that permanently remove greenhouse gases from the atmosphere.
Emissions in real estate
The building sector is responsible for around 40% of global GHG emissions. The potential for reduction is accordingly great – and thus also the responsibility borne by those involved in the industry. To raise awareness of the urgency of rapidly reducing GHG emissions, it is important to know where and when a building emits GHGs throughout its life cycle and how these emissions can be reduced.
The WBCSD study ‘Net-zero buildings: Where do we stand?’ addressed these questions. Based on six example projects, the organisation investigated the level of GHG emissions during the different phases of a building’s life cycle. This revealed that ‘operational carbon,’ i.e. the GHG emissions from operating energy, accounts for almost half of all emissions. ‘Upfront carbon’ (production and materials) accounts for around a third, while ‘embedded carbon’ (emissions from the use phase and dismantling) accounts for a fifth.
Comparing and deciding based on life cycle assessments
A life cycle assessment makes it possible to visualise a building’s GHG emissions. In Switzerland, life cycle assessment data in the construction sector, which covers the GHG emissions of many building materials – from primary structures to façade types and technical building components –, is used as standard for this purpose. However, the values are mostly approximations because no exact data is available for many products. Nevertheless, life cycle assessments are a valuable tool: they can be used to create variants or as a basis for decisions to reduce or avoid environmental impacts.
What options are available for planners and builders to reduce building-related GHG emissions as much as possible? The following measures, among others, can contribute to reaching the net-zero objective:
By the way: our white paper also explains when the most CO₂ emissions occur in the life cycle of a property and how they can be reduced. It shows that it is already possible to approach net zero today.
Renovation or new building?
If the total grey emissions are taken into account, renovation outperforms a new replacement building in many cases. Why? Most of the primary structure is retained during a renovation. As this often consists of concrete and brick, which contain a lot of grey emissions, it is important to use these parts of the building for as long as possible.
Architecture and planning
The climate-friendliness of a construction project begins with the architectural concept. Optimised geometry, a material-efficient building structure, the choice of durable materials and compact structures with a compact supporting structure all contribute to reducing emissions.
Space-saving floor plans
The most environmentally friendly square metre is the one that is not built. That’s why it’s worth thinking about space-saving floor plans. A tried-and-tested solution in residential construction is to reduce individual space requirements and instead offer common spaces such as guest rooms or hobby rooms.
Environmentally friendly building materials
Today, very few construction materials are completely emission-free, but many are at least low-emission. These include building materials of biogenic origin such as wood, insulation materials made from renewable raw materials such as straw or cellulose, and climate-optimised concrete types. As concrete accounts for around 8% of global GHG emissions, it has a particularly large impact. Various companies have developed solutions that significantly reduce the carbon footprint of concrete.
Circular economy and reuse
To limit the climate impact, buildings and components should be durable and reusable. This is the objective of the circular economy: materials and products remain in circulation over a long period rather than being disposed of at the end of their service life, as in a linear economic system. This not only reduces the consumption of primary raw materials, but also generates less waste.
Recycling
Switzerland’s building stock is a huge stockpile of resources, encompassing some 3.2 billion tonnes of material. The more that can be recycled after dismantling, the better it is for the climate. To achieve this, the sorting of construction materials by type should be taken into account as early as the planning stage.
Energy concept
Many properties in Switzerland are still heated with fossil fuels such as oil or gas even though fossil-free operation is now possible at all locations. Suitable solutions for low-emission heating include heat pumps, thermal grids and wood-fired heating systems. It is also important for roof and façade areas to be used for photovoltaics.
Energy-efficient operational optimisation
Energy-efficient operational optimisation a few months after a property has been put into operation is a quick and cost-effective method of ensuring energy-efficient operation. This saves roughly 10 to 15% of operating energy, reducing both costs and emissions. Unlike energy-efficient renovation, operational optimisation is not associated with major investments.
Profitability assured
Building to net zero also has a positive effect on profitability. In most cases, it is now economically more lucrative to use a renewable energy system instead of fossil fuels. Although investment costs are sometimes higher, energy costs are lower. It is important to carry out a cost analysis encompassing the entire life cycle. As a study by the consulting firm Wüest Partner shows, emission-free residential properties are on average more valuable than buildings heated with fossil fuels due to their higher yield potential – even when the higher investment costs are taken into account. Sufficiency measures can also lead to cost reductions, as less space is used and less material is consumed. Timber construction is also often cheaper, as production and processing are less energy-intensive and transport distances are shorter than with other construction materials.
Successful example projects
Various examples show that net-zero construction works not only on paper, but can also be implemented in practice. At the planing mill site in Winterthur, for example, the focus is on measures such as replacing concrete with timber structures or reusing components. Similar methods are also used in the Vergé building on the Greencity site in Zurich. In addition to the choice of low-emission materials, the use of renewable energy from ewz also contributes towards reaching the net zero objective. A third example is the new headquarters of Sonova Communications in Murten. Thanks to high-quality insulation and a large thermal storage mass, the building requires no active heating or cooling, making it operationally carbon-neutral.
Construction measures and an innovative energy concept significantly reduce the CO₂ emissions of the new Vergé building in Greencity.
