The future of sustainable house building |

Building sustainably: just a trend or the future of construction?

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26.04.2022 | 3 minutes

Climate change is prompting questions about sustainability in every sector. Alongside transport and industry, construction accounts for a large share of Switzerland’s total CO2 emissions. Prof. Urs-Peter Menti, lecturer and co-director of the Institute of Building Technology and Energy IGE at the Lucerne University of Applied Sciences and Arts, discusses the future of climate-compatible house building in an interview. He explains what contribution the construction industry, but also every homeowner, can make to achieving Switzerland’s climate targets.

“Sustainable building has become a trend” – is this true? And if so, why?

Prof. Urs-Peter Menti: Climate-compatible construction remained reserved for idealists and pioneers for 20 years, but has now indeed become mainstream. Until recently, people who built an energy-efficient wooden house, voluntarily gave up a car, consciously avoided unnecessary travel or ate a vegetarian diet were ridiculed in many places. Today – at least in urban regions – such attitudes have almost become the norm, although not always with complete consistency. The most likely reason for this trend is the intensified climate debate in society, largely driven by the increasingly noticeable effects of climate change such as hot summers, winters with little snow, and natural events including floods and landslides.

All these factors lead to a greater awareness of ecological issues, or even implicitness, especially among the younger generations. In addition, there is no longer such prejudice about sustainable building being more expensive. Particularly from a lifecycle cost perspective, climate-compatible building has an economic advantage. It may still result in additional investment costs here and there, but the lower operating costs, higher value retention or improved rental possibilities soon compensate for the initial extra cost.

As a result, sustainable building has made great strides in recent years. But what does the future of construction look like?

Prof. Urs-Peter Menti: “Sustainable” building actually covers three dimensions: the environment, society and the economy. However, if we focus on environmental issues, then we can see that there is currently a great momentum, that is following on seamlessly from past trends: the energy crises of the 1970s brought the issue of energy conservation into focus. The aim was to prevent energy losses, for instance by insulating building shells more effectively or by equipping windows with double and triple glazing. Later, the focus moved more and more to renewable energies in an attempt to reduce CO2 emissions and curb climate change.

Does that mean that energy efficiency is no longer important today?

Prof. Urs-Peter Menti: Even though the focus has shifted away from saving energy, energy efficiency is still a key issue when it comes to achieving climate targets. But if we manage to switch our energy supply entirely to renewable energies, then the subject of energy efficiency is likely to recede somewhat into the background. Then the question of whether energy should be saved or whether more energy should be produced will be primarily an economic consideration. But there is still a long way to go until then.

So is switching to renewable energies enough to meet climate targets?

Prof. Urs-Peter Menti: No, because until now, both energy saving and “renewable energies” have focused almost exclusively on the operating energy of buildings. In recent years, however, it has been increasingly recognized that “gray energy” must be taken into account. This refers to the energy consumed during the construction of buildings and, above all, to the energy associated with the building materials, for example for the production, processing and transport of materials. “Gray energy” in construction takes on particular significance with the “net zero” goal, as this is where potential but also immense challenges lie. For these reasons, it is extremely important not only to reduce quantities and to choose local materials, but also to develop materials that emit less CO2 during production. As well as representing a challenge with regard to planning, the reduction of material requirements also promotes the circular economy, which means that used materials are not disposed of when a building is demolished, but are reused in various forms. In the future, the circular economy will play a major role in sustainable, environmentally friendly construction.

You mentioned the impact of building materials on climate compatibility. Which building materials are future-proof?

Prof. Urs-Peter Menti: As already mentioned, these are primarily building materials that produce low 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 interests, putting pressure on concrete and cement, as well as certain other materials. Local, renewable materials, especially wood, are at an advantage. Another material that we are hearing more and more about is clay, mainly because it can often be obtained locally, is easy to work with, and has very good structural and physical properties that have a balancing effect on room temperatures or indoor humidity.

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

Prof. Urs-Peter Menti: There is no single miracle package of measures – each building is too individual and the local conditions too different for that. For new buildings, however, my main recommendation would be to opt for an energy supply that uses renewable energies such as a heat pump, solar system or district heating. It also makes sense to ensure a conscious choice of building materials, such as wood or clay, and to install contemporary building technology such as comfort ventilation or a cooling system. A large amount of daylight should be let in through good 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 matter of course, as is a reasonably compact building shape. However, full sustainability also includes thinking carefully about the location, in particular in terms of accessibility by public transport or mobility requirements. In addition, the floor plan should be flexible to respond to the changing needs of residents. To improve economic sustainability, it is also a good idea to find out about subsidies or special conditions on mortgages. If you observe all these points, you have already done a lot of things right.

Does your property have a sustainability certificate?

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And what should a homeowner consider when renovating an older property?

Prof. Urs-Peter Menti: When renovating a property, the options for action are slightly more limited: there is usually no choice with regard to the building geometry and materials. The focus is therefore on applying energy-saving measures to the building shell, including the roof, walls, basement ceiling and, in particular, the windows, as well as on replacing the heating system and switching to a renewable energy source. An overall concept that takes the specific situation into account is an important part of renovation work. However, an overall concept does not mean that you always have to carry out complete renovation right away, as this is often not financially viable for the owner. Existing properties can usually be successfully renovated in stages. As long as this is based on a well thought-out, comprehensive concept, there is no need to compromise on the end result. As well as renovating the building shell and replacing the heating system, it is always worth checking whether a photovoltaic system can be retrofitted.

So which measures are generally worthwhile in terms of climate compatibility?

Prof. Urs-Peter Menti: There are probably only very few measures that do not pay off in the long run. However, it is always important to take a lifecycle view, since many measures to ensure high sustainability may be expensive in the short term, but will more than pay for themselves over the life of the building or system. In this case, subsidies can relieve some of the investment burden. If the investment volume is limited, it is important to compare and prioritize the various possible approaches for achieving high sustainability and, if necessary, to implement them step by step. This is more difficult if you are trying to improve the quality of the building shell, but it remains possible to install a photovoltaic system after one or two years. If this type of system is envisaged right from the start, it is not usually a problem to fit it later on.

Various research projects are underway at the Lucerne University of Applied Sciences and Arts. What measures are currently being researched in the area of “sustainable building”?

Prof. Urs-Peter Menti:The topic of “sustainable building” is very broad and very diverse – this is also true of our current research projects. But I would like to mention a typical project: as climate change leads to increases in temperatures – especially in cities – and the associated heat island effect, early planning and implementation of measures to prevent neighborhoods from overheating are becoming critical. These measures include the proper positioning of buildings, the right choice of materials for the building shell, green facades and outdoor water features. Appropriate simulation and calculation tools are needed in order to have a basis for decision-making at an early planning stage that indicates which measures will achieve the desired effect. We are currently developing a simulation tool that delivers the required results very quickly and can be interactively integrated into the early planning process. While commercial simulation tools for these types of calculations today typically take 24 hours to produce results, our tool will require computation times of a few minutes at most.

Are you also conducting research in the field of “gray energy”?

Prof. Urs-Peter Menti: “Gray energy” is the energy hidden in materials and in construction processes. It is a known fact that building services can account for up to forty percent of consumption in a building. To minimize “gray energy”, it is therefore important to make the right decisions at a very early planning stage. We have identified where the big levers are and how to get them right early.

What about other research institutes? Are there any other promising research results that you find groundbreaking?

Prof. Urs-Peter Menti: There is a lot happening in this area at the moment. At ETH Zurich, for example, research is being conducted into cement-free concrete that largely retains the qualities of concrete but generates significantly less CO2 in the production process. And the Swiss Federal Laboratories for Materials Testing and Research (Empa) have drawn up clear recommendations for renovation in a widely acclaimed study. They have determined that simply renovating the building shell without replacing the heating system is not enough to meet climate goals. Research is also being done on “colored” photovoltaic panels in many places. Today, photovoltaic panels often still look very technical, which prevents them from being used as a design element as well. The possibility of coloring or printing the elements as desired will lead to a huge increase in the range of possible applications – especially on facades. The slight reduction in efficiency is more than compensated for by the multiplication of possible areas of use. In addition, PV cells are increasingly being integrated directly into facade elements rather than being placed on the outside of facades, which is a great advantage from an economic point of view.

About Prof. Urs-Peter Menti

Prof. Urs-Peter Menti is a lecturer in building technology at the Lucerne University of Applied Sciences and Arts, where he is co-director of the Institute for Building Technology and Energy. His main areas of expertise include sustainable and energy-efficient construction, energy and building technology. Alongside his role at the university, Urs-Peter Menti is active as an expert, advisor and board member as well as a commission and committee member.

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