Eco-design software for more environmentally-friendly construction

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.

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 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.

Fur­ther read­ing
- Peu­porti­er B., Eco-con­cep­tion des bâti­ments et des quartiers, Press­es de l’Ecole des Mines, 336p, novem­bre 2008, http://​www​.press​es​desmines​.com/​e​c​o​-​c​o​n​c​e​p​t​i​o​n​-​d​e​s​-​b​a​t​i​m​e​n​t​s​-​e​t​-​d​e​s​-​q​u​a​r​t​i​e​r​s​.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