Sustainable building just a trend or the future?

Climate change raises questions about sustainability in all sectors. Along with transport and industry, the building sector accounts for a large share of Switzerland's total CO2 emissions. Prof. Urs-Peter Menti, lecturer and co-director at the Institute for Building Technology and Energy IGE at the Lucerne University of Applied Sciences and Arts, talks in an interview about the future of climate-friendly house building. He explains what contribution the construction industry, but also every homeowner, can make to achieving Switzerland's climate goals.

"Building sustainably is the trend" – is this statement true? And if so, why?

Prof. Urs-Peter Menti: While climate-friendly construction was still something for idealists and pioneers in the last 20 years, today it has indeed become mainstream. People who built an energy-efficient wooden house, voluntarily gave up a car, deliberately avoided unnecessary travel or ate a vegetarian diet were ridiculed in many places until recently. Today, at least in urban areas, it has become almost the norm, although still rare with the final consequence. Reasons for this trend are certainly the intensified climate debate in society, significantly also driven by the yet increasingly noticeable effects of climate change with hot summers, winters with little snow or even natural events such as floods or landslides. All these factors lead – especially among the younger generations – to an increased awareness or even a matter of course with regard to ecological issues. In addition, sustainable construction is no longer subject to the prejudice of being more expensive. Especially when you do a lifecycle costing, climate-friendly construction already has an advantage from an economic perspective as well. There may still be additional costs here and there in the investment, but the lower operating costs, the higher value retention or better rentability very quickly compensate for these initial additional costs again.

Accordingly, sustainable construction has made great progress in recent years. But what does the future of building look like??

Prof. Urs-Peter Menti: "Sustainable" construction is actually understood to encompass the three dimensions of environment, society and economy. However, if we focus here on the environmentally relevant topics, then a strong development is currently taking place that follows on seamlessly from past developments: The energy crises of the 1970s brought the topic of energy saving into focus. The aim was to avoid energy losses, z.B. by better insulating the building envelope or by equipping the windows with double and triple glazing. Later, the focus shifted increasingly to renewable energies, with the aim of reducing CO2 emissions and thus curbing climate change.

Consequently, is energy efficiency no longer important today?

Prof. Urs-Peter Menti: Even though the focus has shifted away from energy saving, the topic of energy efficiency is still very central to achieving the climate goals. But if we manage to switch the energy supply completely to renewable energies, then the question of energy efficiency will probably recede somewhat into the background. Then it will be a primarily economic question whether energy should be saved or whether more energy should be produced accordingly. But there is still a long way to go.

So it is enough to switch to renewable energies in order to achieve the climate targets?

Prof. Urs-Peter Menti: No, because up to now the focus has been almost exclusively on the operating energy of the buildings, both in terms of energy saving and the topic of "renewable energies". In recent years, however, it has been increasingly recognized that "gray energy" must be taken into account. This involves the consumption that occurs during the construction of the building and, above all, the energy that is contained in the building materials, e.g. the energy that is used for the construction of the building.B. in the production, processing and transport of materials. With the goal of "net zero", "gray energy" in construction takes on special significance, as this is where potentials but also immense challenges lie. For these reasons, in addition to the reduction of material quantities and the use of local materials, the development of materials that emit less CO2 during production will also be of great importance. On the one hand, the reduction of material requirements is a planning challenge, but it also promotes the circular economy, which means that used materials are not disposed of when a building is dismantled, but are reused in various forms. In the future, the circular economy will play an important role in sustainable, environmentally friendly construction.

You mentioned the influence of building materials in terms of climate compatibility. Which building materials are future-oriented?

Prof. Urs-Peter Menti: As already mentioned, these will primarily be building materials that cause few CO2 emissions during extraction, processing and transport. This is a challenge, because a building needs a certain mass and stability, which often leads to a conflict of objectives. Concrete and cement, but also other materials, come under pressure as a result. Local, renewable materials, especially wood, have an advantage. Another material that keeps coming up is clay, mainly because it can often be locally sourced, is easy to work with, and has very good building physics properties that have a balancing effect on room temperatures or indoor air humidity.

What measures would you recommend to someone who wants to build a single-family house today??

Prof. Urs-Peter Menti: There is no one-size-fits-all package of measures – each individual building is too individual for that, and local conditions are too different. For new buildings, however, I would primarily recommend an energy supply with renewable energies, such as heat pumps, solar or district heating. In addition, a conscious choice of building materials, for example wood or clay, as well as a contemporary building technology such as comfort ventilation or a cooling option is sensible. Daylighting should be kept high with reasonably sized windows, and excellent solar shading should be provided to prevent overheating. A photovoltaic system on the roof or in the facade is almost a given, as is a reasonably compact building shape. However, sustainability also includes thoughts about the location, in particular public transportation access or mobility needs. In addition, the floor plan should be flexible to respond to changing needs of residents. To improve profitability, it also makes sense to find out about subsidies or special conditions on mortgages. If you follow all these points, you have already done a lot right.