Topic: Resources and CO₂
Why project success is climate action — and why it costs nothing extra
Concrete emits when it is built, not when it is used. That makes failed projects a climate factor, and sound process organisation the answer.
There is an argument for lean construction that rarely appears in brochures, because it is hard to sell: it is not about doing something additional. It is about not doing something twice.
The emissions are spent the moment the element stands
Concrete emits during production. Unlike a vehicle or a heating system, nothing follows later — there is no consumption to reduce after the fact. The bill is settled before the building goes into service.
What matters is the consequence: those emissions are only justified through use. A building that is used returns something for the expenditure. If it stays within budget and schedule, that expenditure remains what was planned. On large projects, that is the exception. Projects that fail return nothing at all.
Two thirds cannot be engineered away
Cement production accounts for roughly 6–8 % of global CO₂ emissions, on the order of 2.7 billion tonnes annually. The breakdown is the interesting part: around two thirds are process emissions from the calcination of limestone. They arise from the chemical reaction itself, not from firing the kiln.
A cement plant running on renewable energy therefore reduces emissions appreciably, but not fundamentally. The chemical share remains. The limits of improvement here are hard ones.
This figure is usually cited in support of novel materials and carbon capture. But it also supports something far less exciting: if emissions per cubic metre can only be reduced so far, then the number of cubic metres becomes the decisive variable. And that depends on whether we build correctly. The same reasoning holds for novel building materials.
Three ways it is lost
The unfinished structure. Emissions fully incurred, benefit zero. A total loss. There are no reliable aggregate figures — which is itself notable — but documented individual cases are plentiful.
Demolition after defects. An element is built, found deficient, removed and rebuilt. The emissions occur twice; the result exists once. Measured in carbon, that is a 50 % efficiency.
Quiet rework. The most common case and the worst documented. The Construction Industry Institute puts direct field rework at around 5 % of total project cost on average, with a range of 2–20 % depending on project type. Navigant research reports about 5 % as recorded versus closer to 9 % in reality, since much is never captured. A PlanRadar survey across 15 countries reports more than 11 %. The spread is itself the finding: unrecorded rework is structurally invisible.
Why this argument grows in weight
For typical new buildings, embodied emissions — those from manufacturing and construction — account for 25–40 % of combined construction and operational CO₂ emissions, depending on construction method and efficiency standard. That corresponds to 10–16 kg CO₂ equivalent per square metre of living space per year.
That share rises the more efficient a building is in operation. This is the real point: the better we insulate and the cleaner the grid becomes, the larger the relative share of what is emitted during construction. Build quality and project success therefore become more important as a climate factor, not less.
No trade-off, and therefore no sacrifice
Here is what separates this from most sustainability arguments: it requires no weighing of goals.
Avoiding rework saves money. Making sequences reliable saves time. These are the reasons takt planning, Last Planner and sound process organisation get introduced in the first place — they appear in every business case. The emissions saved along the way require no one to do anything extra or give anything up.
To avoid a misunderstanding: introducing these methods is not free. It costs training, attention and a willingness to question established routines. What costs nothing is the ecological co-benefit — it demands no investment beyond what already makes commercial sense.
That is a less ideological claim than “let us build green”. It is also the more defensible one.
What follows
An element that does not have to be demolished saves money, time and several hundred kilograms of CO₂ per cubic metre of concrete. All at once.
That is why this site is about scheduling, about takt, about Last Planner, and about why method rollouts in construction so often fizzle out. Not because those are the most exciting climate topics, but because they address the point where construction actually loses something.
Sources
Process emissions from cement production. German Federal Environment Agency (Umweltbundesamt): Dekarbonisierung der Zementindustrie (factsheet, February 2020, German). It states that roughly two thirds of emissions come from CO₂ released by the raw materials and one third from fuel combustion. The volumes given there refer to Germany. The global share of cement production in CO₂ emissions is put at 6–8 % depending on the accounting method — a range, not a fixed figure.
Embodied emissions in new buildings. Gebäudeforum klimaneutral, a project of the German Energy Agency (dena): Graue Energie und Emissionen (March 2022, German). Gives 25–40 % embodied emissions for typical new buildings within the German GEG system boundary, equal to 10–16 kg CO₂ eq./(m²·a), and describes how this share rises as operational efficiency improves.
Rework costs. PlanRadar: The cost of rework in global construction — a customer survey across 15 countries with more than 2,500 responses, reporting over 11 % of project cost. The caveat belongs with it: this is a software vendor surveying its own customers, not an independent study.
The Construction Industry Institute figures (around 5 % on average, range 2–20 %) and the Navigant figures (about 5 % recorded versus closer to 9 % in reality) are cited here from secondary sources. I have not seen the original publications — if you have them, do get in touch.
CO₂ per cubic metre of concrete. Deliberately given only as an order of magnitude. The value varies considerably with strength class, cement type and clinker factor; a single number would be false precision.