Bioclimatic architecture

Bioclimatic architecture means putting a place's climate to work in place of machines: orientation, shade, mass, the window one opens at night. It is an approach, not an exact science.

We say so from the outset because it is the most useful thing we can say. Serious studies contradict one another. The same dwellings, measured the same summer, go from 88% overheating to 71% too cool depending on the criterion chosen ¹. And the heaviest factor of all is not in the wall: it is in what an occupant does at eleven o'clock at night.

That does not mean we know nothing. It means we know a ranking rather than a figure, and that under those conditions intuition, experimentation and sensitivity to the way people live come before calculation. Calculation comes afterwards, to check, and sometimes to say no.

This page first tells the problem, then what others found before us, then why it is difficult. Our point of view comes at the end.

First false certainty: what the body feels is not the air temperature. It also feels the radiation from surfaces, that is, the heat that walls and above all glazing send back onto the skin, then humidity, then air movement. Standards in fact work with a composite quantity, the operative temperature, the average of air and radiation ²: in a heavily glazed, unprotected room at the end of the afternoon, it is well above what a thermometer shows. One room can therefore be "at 27 degrees" and unliveable, another "at 27 degrees" and bearable.

Second false certainty: that a threshold exists. The French reference campaign followed 76 flats in collective housing for four months, with comfort reported three times a day ³. It gives empirical thresholds: comfort around 25 degrees, discomfort beginning at 26, strong discomfort from 28. Above all it gives the spread: for each comfort level, 80% of the answers fall within a range of about 4.5 degrees ³. In the same flat, at the same temperature, the gap between two people is wider than the gap between a good and a bad project. (CSTB and Union sociale pour l'habitat, RENOPTIM project, 2025.)

Tolerance also shifts over time. That is adaptive comfort: after a mild week, 27 degrees feel like a lot; after ten days of heatwave, bearable. French regulation takes it into account, but bounds it in two instructive ways: it caps adaptation at two degrees, and it does not apply it at night ². Because adapting presupposes being able to act, and one does not act while asleep, nor at eighty years old when one no longer goes out.

Hence the most unsettling point: the result depends on the criterion as much as on the building. Of 282 dwellings in Leicester measured the same summer, 88% of bedrooms are classed as severely overheated under a fixed-threshold criterion, and 71% judged uncomfortably cold under an adaptive criterion ¹. (Lomas and Kane, 2013.) Any sentence of the form "X% of dwellings overheat" is inseparable from its criterion.

There remains the question that decides everything: why night matters more than day.

Because night is when the body recovers, and night is when the building discharges its heat. A case-control study of the Paris heatwave of August 2003 compared 241 people who died with 241 controls: the minimum night-time temperature of the neighbourhood is significantly associated with death, with an odds ratio of 2.17 per 0.41 degree of difference, whereas the mean temperature over day and night is not ⁴. (Laaidi et al., 2012.) A second study of the same heatwave adds the architectural consequence: having one's bedroom directly under the roof multiplies the risk of death by four ⁵. (Vandentorren et al., 2006.)

The problem of summer comfort is therefore not that it is hot at three in the afternoon. It is that the room does not come back down at night.

Before machines, centuries of builders dealt with this problem without an engineer and without electricity. The common thread is counter-intuitive: none of these devices makes cold. They shift heat in time, they flatten its amplitude, or they intercept it before it gets in. The wind tower is the most badly told example: on a badgir in Kashan, the incoming air is at 17 degrees at three in the morning and 34 degrees at three in the afternoon, that is, the outdoor temperature ⁸. The cooling came from the water of the qanat below ground, not from the tower. (Hejazi and Hejazi, 2012.)

The cave dwelling says it another way: at the rock-cut site of Meymand, the difference in mean temperature from outdoors is only 1.6 degrees, but the standard deviation falls from 2.73 degrees to 0.40 ⁹. It is the smoothing, not the drop, that makes the place habitable.

Morocco wrote it in earth, at the scale of an entire village. The ksar of Aït Ben Haddou, on the Ounila valley, between the High Atlas and the desert, is built entirely of raw earth: rammed earth for the walls, adobe bricks for the upper parts, timber for the floors. It has been a World Heritage site since 1987 ¹⁰. The climate is handled there by three things at once. Material: thick walls that give thermal mass, the kind that smooths out the day. Density: houses built against one another, narrow streets, covered in places, where each façade shades the next. Exposure: a village set against its hill and turned towards the valley, sheltering itself from hot, sand-laden winds. In Fez, the same logic enters the house: the dar is organised around a narrow, tall patio, open to the sky, which keeps the cool air of the night and shades the house with itself; the mashrabiyas filter the sun and the gaze. None of these buildings has been instrumented in any publication we have found: this is the account of an architecture that has held for centuries in a harsh climate, not a measurement.

The perforated screen, the mashrabiya, says the most directly useful thing. Placed in front of the window and not behind it, it stops the sun before it has crossed the glass. The contemporary equivalent is quantified: an external blind lets through a total solar factor of 0.05 on double glazing, against 0.43 for the same blind fitted inside ¹¹. A factor of eight, for twenty centimetres of displacement. And at equal consumption, the share of glazing in the façade rises from 4% with a bare window to 22% with an external screen: it is external shading that makes large glazing sustainable, not high-performance glazing ¹². (Sherif et al., 2012.)

Then comes the counterpoint, and it is not negotiable.

Thermal mass is not resistance. It is the most widespread confusion on the subject. A heavy mass does not hold heat back: it spreads its arrival over time. The French reference campaign, on an instrumented rammed-earth house in Isère, measures six hours of time lag, that is, of delay, between the outdoor peak and the peak inside the wall, for 50 centimetres of thickness: six hours, not the ten to twelve one reads everywhere ¹³. And the thermal resistance of that wall is 0.29 to 0.87 square metre kelvin per watt, the equivalent of two to three and a half centimetres of mineral wool ¹³. The level required today of a renovated wall is 3.7 ¹⁴: a factor of three to ten. The authors put it themselves: a rammed-earth wall is more insulating than a stone or concrete wall, but it cannot be called insulating ¹³. (Heitz et al., 2015.) A Haussmann-era wall of 50 centimetres of stone is worth about 0.3; a 20-centimetre concrete wall, about 0.10 ¹³. These buildings are not insulating. They are slow.

And these techniques worked in their climate, with their way of life. The study on perforated screens states its own domain of validity, between 14 and 40 degrees north latitude ¹²: Paris is at 48.85. The mean wind in Paris is 3.2 metres per second ¹⁶, just at the operating threshold of a wind tower ¹⁷, and our heatwaves, anticyclonic, are most often nearly windless. These devices also assumed a house occupied all day long, where someone opened at the right moment. The message is therefore not "let us go back to the vernacular"; it is: let us sort out what the physics of 2050 still validates.

The twentieth century invented the modern tools of solar control. It invented them by getting it wrong first, and that is the most instructive story on this page.

The founding failure. In 1933 the Cité de Refuge of the Salvation Army opened in Paris, by Le Corbusier and Pierre Jeanneret: a building entirely sealed, without a single opening window. The air was to be manufactured by a machine, behind a south façade of double glazing with treated air circulating through it, the "neutralising wall" developed with the engineer Gustave Lyon. For lack of money, this device was never built: the building received single glazing and ordinary heating, while keeping its airtight skin. More than a thousand square metres of glass facing due south, with no opening light and no solar shading. As early as 1935, a court ruling required a window to be cut into each bedroom within forty days. After the glazing was destroyed by a bomb in 1944, Le Corbusier himself placed a brise-soleil in front of the new windows ¹⁸¹⁹²⁰.

The lesson holds word for word today: airtightness, solar gains and ventilation form a system, and removing one member turns the other two into defects. It is the mechanism behind the overheating of high-performance buildings, ninety years later. Let us also say what we do not know: no measured temperature has ever been published for this building.

The invention that came out of it. The brise-soleil was born there: stop the sun before it passes through the glass, with a geometry calculated for the latitude and the orientation. Algiers in 1933, Rio in 1936, Marseille, then Chandigarh ²¹²². In Rio, the Brazilian architects led by Lúcio Costa, with Oscar Niemeyer and Affonso Reidy, go further: they make the louvres adjustable, operated by hand through gears and counterweights ²³²⁴.

What these buildings taught afterwards. A fixed louvre is optimal at only one orientation and one latitude, and it is poor to the east and the west, where the sun is low and raking: that is the hardest case in Paris, where nearly four metres of overhang would be needed to shade a full-height opening at the end of the afternoon ²⁵. A massive concrete louvre must moreover be ventilated on its rear face, otherwise it stores the day's heat and radiates it back in the evening. At Chandigarh, one now sees air conditioners installed in the very loggias that the brise-soleil was meant to make unnecessary ²⁶.

And Rio's movable louvre turned a design problem into a fifty-year maintenance problem: the restoration begun in 2014 recorded the oxidation of the mechanisms and the fall of several panels, and put back into working order about one thousand one hundred window assemblies ²³. A movable shading device that is no longer operated becomes a fixed one, badly oriented: that is the normal failure mode, not the exception. The right question is therefore not "does it work", it is "who will maintain it, thirty years from now, and with what budget".

More disturbing still: New Gourna, the village that Hassan Fathy built in Egypt from 1946 to 1952, was thermally right, economical and celebrated. It remained largely uninhabited ²⁷²⁸. One can be right about the physics and wrong about the people.

And a fact that must be faced. None of the buildings cited here has published thermal measurements: not the Cité de Refuge, not Chandigarh, not Rio, not New Gourna. The history of bioclimatic architecture is a history of intentions and accounts, very little a history of data. This is not a reproach aimed at those architects: it is the reason why being serious does not consist in imitating them, but in measuring what one builds oneself.

Here is the part we would rather not have written, and which is the most useful.

Insulation weighs far less on summer than people think. The largest study available simulated 576,000 building variants to isolate the weight of each parameter. Wall performance explains only 3.5% of the variance in overheating duration and 2.9% of its severity: less than 5% in the worst case. Orientation, solar shading, ventilation and occupant behaviour dominate by a very wide margin. The authors add that they find little sign that increasing insulation increases overheating, except where opening the windows becomes impossible ²⁹. (Fosas et al., 2018.)

Other campaigns say almost the opposite, and they are just as serious. Across 616 living rooms and 591 bedrooms measured and weighted to the English housing stock, the prevalence of bedroom overheating falls from 17.9% with less than 150 millimetres of loft insulation to 8.1% beyond it: here, insulation is measured as protective ³⁰. (Study for the British energy department, 2024.)

One must also look at who signs. The reference study most favourable to thermal mass is a hundred-year life-cycle assessment of an English house declined in four construction weights, from timber frame to heavy concrete. The heavy versions cost up to 15% more embodied carbon at the outset, but up to 17% less over the whole cycle, because they push back the year in which air conditioning gets installed ³². The article is published in a peer-reviewed journal, its method is explicit, and it is co-signed by the British cement association and by the concrete promotion body. That does not make it wrong; it obliges one to read its assumptions: the benefit assumes six air changes per hour obtained by opening the windows every time the room is too warm and the outdoor air is cooler ³². A perfect occupant, every night, for a hundred years. Field measurements say that occupant does not exist. (Hacker et al., 2008.)

On carbon, the choice of data source weighs more than the choice of construction. The gap between a timber structure and a concrete structure, for the same building, varies strongly with the inventory data used. The international expert group that compared the case studies puts it without ambiguity: the results for timber construction are considerably affected by whether or not the carbon stored in the material is counted ³³. (International Energy Agency, EBC programme, Annex 57.)

None of this says we know nothing. It says that the level is uncertain and the ranking is solid: from one study to the next, the same levers always come out on top, namely orientation, the share and placement of glazing, solar shading, the capacity to ventilate at night, and occupant behaviour. The figure attached to each moves a great deal; their order, hardly at all. A young science feels its way, that is normal, and it is no excuse for doing nothing: one designs very well on a robust hierarchy. It is, on the other hand, a reason never to confuse a calculation result with a truth.

An occupant who does not open the windows at night cancels out the best of projects. This is not a turn of phrase: it is what the campaigns find first, every time.

The order of magnitude is poorly known. Background ventilation, the kind that runs permanently and that nobody ever notices, renews about half a volume of air per hour ³⁵. Clearing what a room has stored during the day takes six to ten ³⁵³⁶, twelve to twenty times more: not a window ajar, a window wide open, if possible on two opposite façades, all night. And it costs the façade's acoustic insulation, in its entirety: an open window is no longer a façade, and in a lively street, at eleven at night, nobody opens. Add security on the lower floors and the habit of closing up before sleeping.

Measurement is severe on this point. The French campaign on 76 flats followed for four months concludes, in black and white, that it was not directly observed that dual-aspect dwellings are at lower risk of overheating, nor that those fitted with external movable solar shading are ³. In both cases, the same cause: it is management by the occupant that conditions the effect. During a heatwave, only 20% of days correspond to ideal thermal management behaviour, and about 30% of occupants change nothing in their habits ³.

The clearest result comes from Belgium. Across 23 highly insulated houses followed for a full year, no significant difference appears according to the presence of solar shading, nor according to whether it is internal or external, nor according to the type of construction. A single variable stands out, with a large effect: opening the windows at night ³⁷. (Dartevelle et al., 2023.)

Winter gives the order of magnitude of this effect. The first assessment of the Elithis tower in Dijon, announced as energy-positive, shows photovoltaics that keep 96% of their promise and a consumption three times higher than predicted ³⁸. The item that runs away is heating, tripled because the setpoint was raised from 20 to 22 degrees, 20 being judged uncomfortable ³⁸. Two degrees of human judgement weighed more than all the engineering of the building.

Misuse of natural ventilation is therefore the factor that weighs most on the discomfort actually measured. The decisive question is not thermal, it is architectural: what makes a human being, in July, at eleven at night, in a real street, want to open the window?

The answer lies in decisions of plan. Where the bedroom is. Whether there is a second façade, and whether it faces a planted courtyard rather than the boulevard. Whether there is a shutter that lets air through while staying closed. Whether one can open without being seen, without being heard, without being afraid.

This is where architecture is decided, not in the spreadsheet.

A practice that delivers is a practice that compromises. To publish only the exemplary case would be to publish a brochure. So we take four: four climates, four programmes, and four answers that have almost nothing in common. If bioclimatic design were a recipe, these buildings would look alike. They do not, and two of them include active cooling that we are not going to hide. For each one, we state the device, what it produces, and the condition without which it produces nothing. A device without its condition is not an explanation, it is a sales pitch. The environmental engineering of three of them, L'Arbre Blanc, the BEM and the Cité de l'Innovation, was carried out with Atelier Franck Boutté, environmental co-designer ³⁹⁴⁰⁴¹.

Twenty-four thousand square metres of housing, developed between 2017 and 2024 with Nexity, delivered ⁴². The flats have no air conditioning ⁴². It is the most committing statement on this page, and it is worth nothing unless we say what holds it up.

The site first, the plan afterwards. The land was wooded, and its qualities were taken into account from the start, as a project given rather than a constraint to be lifted: keep the healthy trees, protect the biodiversity already in place, then set the volumes in the gaps, that is, in the clearings ⁴³. One can read that as a landscape decision; it is first of all a thermal decision, and the first of the project: it fixes where the shade falls, where the air passes, what each façade sees and what it receives. It is taken at sketch design stage, and it cannot be recovered afterwards.

Then, stop the sun before the glass. The solar shading is external, and its density changes with orientation ⁴³. A south façade, an east façade and a west façade do not receive the same sun, nor at the same hours, nor at the same angle; giving them the same screen is getting it wrong at least twice. This page has recalled it: a fixed louvre is optimal at only one orientation, and shading placed in front of the glass does not have the same order of magnitude of effect as the same shading placed behind it. It is what makes large glazing sustainable.

Then the balcony, which is not only a balcony. Balconies amounting to 30% of the floor area made it possible to protect the façade well ⁴³. An overhang of that size is solar shading in the strict sense, and an extra room, available at the time of year when the interior is less so.

Then ventilate, which is the difficult part. The patios and the multiple orientation of the flats allowed natural ventilation of every flat ⁴³: each dwelling has more than one façade and an air intake that is not limited to the street. But this page has been severe on this point: the French reference campaign does not find that dual-aspect dwellings overheat less ³, because the cross-flow only serves if someone opens. So the project moved part of the device to where the human gesture is no longer required: the halls are open ⁴³. Air circulates through them permanently, ventilation is continuous, and in the evening the building cools down thanks to the mistral ⁴³. That gives it a real night life, and it is the best sign that a device works: people are outside at night.

And the condition, which is not a footnote reservation. Proper use and protection of the façades are necessary for it to work well ⁴³. An occupant who leaves the shading raised in the middle of the day, or who never opens, cancels out part of what was built for them. We sought to make the right gesture easy and pleasant, not to make it unnecessary: nobody knows how to make a building that does without its inhabitants.

A tower of 113 flats, 10,000 m², 22 million euros excluding VAT, designed from 2014 and delivered in 2019 ³⁹⁴⁴.

The flats there are air-conditioned ⁴⁴. We would rather write it than let it be discovered. The building's stated performance is that of the thermal regulation applicable at the time, nothing more ³⁹. This project does not demonstrate that one can do without machines, and presenting it that way would be dishonest.

Its real climatic quality lies elsewhere, and it is instructive. The cantilevers do not protect only the flat they belong to: they shade one another, and filter the sun before it reaches the openings ⁴⁴. The radiation is intercepted outside, before it has crossed the glass and been trapped in the room. The engineer who worked on the project does not describe them as balconies but as true environmental interfaces: spaces that passively render services to the building, "outdoor extensions of exceptional dimension" ³⁹. The work bore explicitly on the bioclimatic contribution of balcony-type outdoor spaces, drawing on the environment to increase efficiency, in his words, "with less effort and at lower cost" ³⁹.

It is the same element as in Marseille and it is not the same trade. At ART'CHIPEL, the outside serves first to move the air; here, it serves to intercept the sun and to move life. The gesture looks alike, the reason is different: that is why there is no recipe.

The lesson, told honestly, fits in one sentence: summer comfort is won outside, before coming in. Moving life onto the balcony for a large part of the year is better than nothing, and better than any high-performance glazing without shade in front of it. But it is not the same thing as doing without air conditioning. The condition, moreover, is precisely that: these surfaces keep their promise only if they are actually lived in. An outdoor extension that ends up as storage becomes a mere sunshade again. It goes on shading, which is not nothing, but half the benefit has gone.

9,142 m² of floor area, 23.5 million euros excluding VAT, from a 2014 competition and delivered in 2023 ⁴⁰. Seven grandes écoles, France's selective higher-education schools, pool their teaching rooms there ⁴⁰⁴⁵. The programme has nothing in common with the two previous ones: dense, intermittent occupation, governed by the class timetable, and nobody lives there.

The device is a façade that breathes on its own. Motorised vents open and close according to the hour and the season ⁴⁵. Ventilation is natural: it airs and cools the large volume of the hall, which avoids resorting to air conditioning ⁴⁰. And the hall acts as a thermal buffer for the classrooms ⁴⁰: the classrooms do not open directly onto the outside, they open onto a volume that is already tempered. The engineer speaks of a "variable seasonal porosity", and of an inside and outside no longer separated by a line but "within thick, blurred and shifting limits" ⁴⁰.

One point deserves to be linked to what this page has said about comfort. The outdoor conditions were transcribed as a sensory temperature, close to the operative temperature defined above, not as an air temperature ⁴⁰. It is the quantity that corresponds to what a body actually receives, radiation from surfaces and air movement included, and it is the one that adaptation bears on. Designing on air temperature, in a building like this one, would amount to optimising a figure that nobody feels.

The condition here is of another order, and it is serious. What a dwelling asks of its occupant, this building asks of a machine and a maintenance contract. We saw above what becomes of a movable shading device that nobody operates any more: a fixed one, badly oriented. A motorised vent poses the same problem with a wearing part added. A control system badly set, a maintenance season skipped, and the building closes in on itself without anyone noticing before the month of July. The right question is not whether it works at handover. It is who will maintain it thirty years from now, and with what budget.

15,711 m², under way since 2011 and in progress, within a team led by BIG with OXO ⁴¹⁴⁶. A dense Paris site, a research programme, high internal gains: neither the climate nor the constraints of the first three.

The building is hollowed out at its heart. This void brings light to the centre of the volume and creates a microclimatic zone, a piece of climate made by the form rather than by a machine ⁴¹. The atrium so obtained does two opposite jobs depending on the season. In winter, it serves as a buffer and limits the heat losses of the inner façades that face onto it. In summer, opening its lower part removes the internal loads by natural ventilation, supplemented by night purge ventilation ⁴¹. It is the pair this page has described: discharge at night what the day has deposited.

The most precious fact in this whole file lies elsewhere, and it concerns light. In this single building, the engineer distinguishes three daylight needs. High where daylight autonomy actually makes it possible to reduce artificial lighting, that is, where daylight replaces energy. Limited where glare on screens and summer comfort demand the opposite, because the internal gains are already high there and every additional ray is a load to be removed. Low elsewhere, quite simply ⁴¹.

More light is therefore not better: it depends on the use. A standard states a minimum, the same everywhere, and a project content with meeting it manufactures comfort in one room and discomfort in the next. Here, three different values coexist in a single building, and each is justified by what happens there. It is the clearest demonstration that bioclimatic design is not an accumulation of standards: a spreadsheet adds up requirements, a project arbitrates between them, and arbitrating requires knowing what people do in the room.

What must be said to remain honest. The project also includes active cooling: the passive device reduces the need, it does not remove it ⁴¹. The structure is concrete, partly lower-carbon ⁴¹, which is an improvement and not an exemption. And the resource on which night purge ventilation depends is shrinking with the climate, as this page wrote above. Finally, the building is not finished: we describe here a design, not a building as lived in.

None of the four has been the subject of a year-long measurement campaign. That is not the custom in France: one delivers, one does not measure, and the opportunity to instrument a scheme over a whole season has not yet been given to us. We are working to change that.

We do, however, have the feedback of those who live there. At L'Arbre Blanc, residents report an energy bill reduced by about 30% compared with a conventional flat ⁴⁷. At ART'CHIPEL, the device works: the flats get through the summer without air conditioning, except for a few days of the last great heatwave, in some flats where the solar shading had not been lowered during the day ⁴⁷. That is, word for word, the condition written on the section: proper use and protection of the façades are necessary for it to work well.

This feedback is self-reported, not measured, and we present it as such. It says that the principle holds, and on what condition. We also say which of these buildings is air-conditioned, what depends on an occupant and what depends on maintenance. The next step is an instrumented scheme over a full season, and we want to be the ones who publish it.

A label certifies that a project has passed a threshold in a calculation. That is useful: it imposes a common language and forces one to write down one's assumptions. But it says that the calculation passed, not that the building will, and that the chosen criterion was met, whereas we have seen that the criterion makes the result.

Measurement confirms it. Of 121 certified American buildings that supplied a full year of actual consumption, more than half deviate by more than 25% from their own prediction, in both directions ⁴⁸; and a re-analysis matching each of them to an equivalent ordinary building finds no statistically significant relationship between the level of performance targeted and the consumption measured ⁴⁹. In practice, a project that aims for a label ends up obtaining it: the teams know the criteria, they design for them, and the assessment is made on the file. This is not fraud, it is the normal working of an administrative threshold, but it distinguishes very poorly between the project that was thought through and the one that was optimised. We make of it neither an argument nor a reproach: we note that one does not find there the answer to the only question that interests an occupant, that of knowing whether they will be comfortable at home in the month of July.

We read the site before drawing. Sun paths hour by hour, prevailing winds, noise, shadows cast by the neighbours, and things that cannot be calculated: where people already sit in the shade in July, what the street does at night.

Then we draw by intuition. An architect who has spent a day on a plot knows, before any calculation, where the good rooms are and which façade is the difficult one. That knowledge is not a feeling, it is an accumulation of cases. We start from there, because a calculation only answers the question it is asked: it will never tell you that the bedroom should be on the other side, it will tell you what a bedroom on this side gives.

Then we test, and we get it wrong. We move the room, deepen the balcony, turn the plan around; many of these attempts yield nothing, some change everything. It is experimentation that produces the project, not optimisation. Calculation comes at the end, to check, and sometimes to say no. Never the other way round.

This order has a simple justification: the decisions that count are all taken at sketch design stage, and there they are free. Orientation, depth of the room, share and placement of glazing, the possibility of cross ventilation, shading in front of the glass rather than behind it. Three months later, they cost dearly; three years later, they can no longer be recovered.

Last point, and it works against our interests: we are not the provider of the solution we recommend. On a real project, the regulatory calculation must be doubled with a dynamic thermal simulation on a future weather file. That is the work of an engineering consultancy, not ours.

Below you will find a simulator. It comes at the end of this page, and that is deliberate: it is of no use before the problem has been understood. It models the most exposed room of a Paris flat, a single façade, without air conditioning, by an hour-by-hour heat balance over a real season ⁵⁰. It has no regulatory value, it sizes nothing, it does not model your building: it compares sketch-design decisions and shows which one carries weight.

Simulating a perfect architecture is a delicate exercise, and the tool says so itself. Push every slider to its virtuous stop: you get a room with minimal glazing, shutters closed, very heavy, open all night. That configuration wins on the indicator and loses everywhere else. It costs light, carbon and decibels, and nobody wants to live in it. That is not a project objective. A good project does not tick every box, it chooses which ones.

A project, a plot, a question of summer comfort: write to us.

We will answer with the geometry of your site, and with what we do not know.