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​.presses​de​smines​.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