Ecodesign environmental aspects takes into account when developing a product and is an approach that can be applied to buildings. In addition to the carbon footprint, the impact that construction materials have on health, biodiversity and natural resources must be considered. The choice of materials influences the energy needs of a building, so the entire life cycle of these, from manufacture to end-of-life needs to be optimised.
We are developing software tools to facilitate the design process to meet these objectives. It is possible to develop a simplified model in the initial design phase or to use a digital model known as a building information model. These tools allow architects and engineers to optimise building projects in terms of energy balance, thermal comfort and environmental impact by varying various parameters and analysing the final result. These parameters concern the building itself (insulation and thermal inertia) and the systems installed in it (heating, cooling, ventilation), but the evaluation also takes the climate and the behaviour of the building’s inhabitants into account.
Such an eco-design approach is becoming ever more popular in the building sector. The goal is to make relevant decisions as early as possible in the design process of a building, as these are the ones that will have the greatest impact on the environmental performance of a project in the end. This is why it is useful to have software tools that allow us to easily compare various architectural and technical parameters and, for example, to choose the orientation of a building and the size of windows to improve energy efficiency. After this preliminary phase, we can then optimise the choice of materials to be used to construct the building. It is, for example, better in terms of environmental impact and resilience to heatwaves, to have an inert layer of raw earth or masonry on the inside of a building and an insulating layer of bio-based materials on the outside – rather than mixing these materials in hemp or wood concrete.
We can also compare the viability of a potential project with benchmarks that we have obtained following thousands of calculations to evaluate the minimum and maximum impacts of different types of buildings. For example, we have calculated how many kilograms of carbon dioxide (CO2) equivalent are emitted per square metre per year by different buildings. This gives us a minimum and maximum value for this parameter – which, in general, is between 10 and 120 kg CO2/m2/year for housing. The building’s designer can then assess how his or her project compares to these reference values and, if the environmental impacts are too high, the project can be further improved.
Life cycle assessment
We assess the impacts over the entire life cycle of a building, all the way from the manufacture of the construction materials to the stages of use, renovation and end-of-life. This is an environmental engineering method known “life cycle assessment”. While such calculations first appeared in the late 1980s, from 2022 onwards they will be required by law for all new buildings to ensure that greenhouse gas emissions are being reduced. This is an important step forward, although some aspects of the regulations still need to be improved.
As well as greenhouse gas emissions, the impact of construction projects on human health, biodiversity and environmental resources also needs to be assessed. These impact assessment approaches are being developed in research laboratories across the world and are increasingly appearing in standards, such as the ISO and CEN (European Committee for Standardisation). Our approach is somewhat analogous to the World Health Organisation’s (WHO’s) indicator for healthy life years, called DALYs (disability adjusted life years) and allows us to evaluate the potential health impact of a building in terms of the toxic substances it might generate as well as the consequences it might have for the climate.
To assess the potential impact of a building on biodiversity, the indicator we use is the percentage of species that are likely to disappear because of this building over a certain area and over a certain time. This indicator takes into account the effect on climate, acidification and eutrophication. The latter phenomenon is caused by substances that act as fertilisers, which then pollute rivers and deplete them of oxygen. Land use also needs to be considered.
New buildings versus old buildings
New buildings represent only about 1% of all new constructions each year. If we want to reduce the overall environmental impact of a building, we must therefore also renovate existing constructions. This can pose a problem for historical monuments or, for example, old buildings in cities, whose facades cannot be insulated from the outside. This means they have to be insulated from the inside, which means losing precious living space.
Fortunately, our modelling and software work just as well for both old and new buildings. Indeed, we have worked on many projects spanning a wide variety of sectors – from domestic housing to offices and schools. We have therefore had a lot of opportunities to test our tools and evaluate various designs when it comes to renovating both new and old buildings. It is then up to design offices and architects to integrate these tools into their daily work.
One of our optimisation techniques, based on “genetic algorithms”, has been particularly popular with house builders. This tool works rather like a farmer choosing the best animals to develop his herd over several generations. Our “genes” can include the thickness of insulation and the surface area of window glass, for example. From generation to generation, we choose the gene combinations that produce the best performance in terms of environmental impact and construction cost. We then provide our recommendations to builders.
- Peuportier B., Eco-conception des bâtiments et des quartiers, Presses de l’Ecole des Mines, 336p, novembre 2008, http://www.pressesdesmines.com/eco-conception-des-batiments-et-des-quartiers.html
- Wurtz A., Peuportier B., Application de l’analyse de cycle de vie à un échantillon de bâtiments pour l’aide à l’évaluation des projets, Conférence IBPSA-France, Reims, novembre 2020
- Recht T., Robillart M., Schalbart P., Peuportier B., Éco-conception de maisons à énergie positive assistée par optimisation multicritère, Conférence IBPSA France, Marne-la-Vallée , mai 2016