A green claim on a new home should arrive with its unit of measurement

The vocabulary of green housing marketing was built in a period when nobody was asked to prove it. Words such as eco-friendly, low-carbon, sustainable and responsible appeared on brochures, site hoardings and the names of whole product ranges, and buyers had no way of testing them. My position is that a residential developer should stop using environmental adjectives altogether and publish, for each building, a short set of measured figures with their units, the regulatory baseline they are compared with and the stage at which each was produced. Where a building is merely compliant, the sheet should let that show.

I hold this view partly because the law has moved. French law has restricted claims that a product is carbon neutral since 2023. The European directive on empowering consumers for the green transition, which member states apply from the autumn of 2026, goes further: it prohibits generic environmental claims where the trader cannot demonstrate recognised excellent environmental performance, and it prohibits presenting requirements that the law imposes on all products as a distinctive feature of an offer. I am not a lawyer, and each company should take its own advice on how these rules apply to it. But their direction is plain, and a marketing function that waits for the first enforcement case before changing its vocabulary will have waited too long.

The stronger reason is that the adjectives were never very informative, and some of them misled buyers in a way the industry had stopped noticing.

The legal minimum is not a feature

Every new home in France is built under an environmental regulation that limits energy demand and the carbon emitted in constructing and running the building, and its carbon limits tighten in steps over the decade. A building that meets the regulation is a lawful building. It is not thereby a low-carbon building in any sense a buyer would take as a distinction, because every competitor's building meets the same limits.

At Valcerne we had a range called Clairière, which my own team launched in 2019 as our low-carbon home. By 2024 the name was on 38 programmes. When our sustainability director and legal director reviewed them that year, eleven had embodied carbon at least 15% below the threshold for their permit year. Twenty-one were within 10% of it, and six barely cleared it. In two brochures we had described the insulation as bio-sourced, which was accurate for the roofs and for nothing else. The name made a single claim about 38 buildings that differed considerably, and for most of them that claim amounted to obeying the law.

Nobody had set out to mislead. The range had been created when the better buildings made up most of our launches, and it had spread because sales teams liked it. That is how most misleading claims arise in my experience: not from a decision to deceive, but from a word that outgrows its evidence while nobody is responsible for pruning it.

Units, baselines and the stage of the figure

We took the Clairière name off all 38 programmes by March 2025 and replaced it with a one-page data sheet for every building, whatever its performance. The sheet has a fixed format. It gives the energy performance class and estimated annual consumption per square metre; embodied carbon per square metre, with the regulatory threshold for the permit year printed beside it; the heating system and its energy source; the share of bio-sourced materials by weight; and the walking time to the nearest rail or tram stop, because location shapes a household's emissions more than most construction choices do.

Three features of the format matter more than any single figure. The first is the unit: a buyer can compare kilograms of carbon per square metre across buildings and developers, which nobody can do with an adjective. The second is the baseline: printing the legal threshold beside each figure stops a compliant building from passing for an exceptional one. The third is the stage. Most figures available when a home is sold are design estimates, and as-built performance can differ. We failed to label the stage during our first five months, and when one building in Montpellier came in 6% worse than its design estimate, we had to correct its sheet and write to its buyers. Every figure now states whether it is an estimate or a measurement.

What we lost when we stopped saying low-carbon

The decision had costs, and they belong in the argument. We wrote off €1.1 million of signage and sales material across 22 sales pavilions. We gave up a name that more than a third of home-seekers in our agency's Lyon panel recognised when prompted. Our sales team believed Clairière lots carried a premium of about €90 per square metre, and expected to lose it. Our chief executive first proposed keeping the name for the eleven better buildings. I argued against that because our internal threshold was not a recognised standard, so the name would still be a generic claim implying excellence, and buyers would take it as a description of the company rather than of eleven buildings.

What followed was more interesting than either of us expected. In 2025, homes in buildings at least 15% below their carbon threshold still sold for about €70 per square metre more than comparable homes nearby. Elsewhere we could measure no premium at all. The premium had never belonged to the word. It belonged to the buildings that earned it, and buyers found them on the data sheet. One institutional investor cited the sheets in its due diligence before buying 148 homes in Montpellier.

The argument has limits. A one-page sheet is harder to market than a name, and a developer whose buildings are mostly compliant will find that its sheets look ordinary. I think that is the honest position, and it creates pressure to build better rather than to describe better. Smaller developers may lack the data systems we had to build, though the core figures already sit in every permit file. And some buyers want reassurance rather than numbers; for them, a sales adviser who can explain the sheet matters more than the sheet itself.

I would ask any developer's audit committee to pick one environmental sentence from a current brochure and request the evidence behind it, with its unit, its baseline and the date it was produced. If that evidence takes more than a day to assemble, the sentence was not ready to be published.