What matters now?

We want to avoid emissions. Not someday, but now. Then a building decision has to show which emissions it triggers today — and which emissions can be avoided today.

An LCA over the entire life cycle answers a larger question. It combines production, building services, operation, replacement and end of life over a long reference period. That matters: we want to understand a building’s total climate impact. But for a decision today, we also need a view that keeps today visible.

Where the difference gets smaller

In our comparison, two functionally equivalent building variants differ by 83.24 tonnes CO₂e in A1–A3. In the 50-year total, the gap is only 44.91 tonnes. We can now locate where that reduction happens: not in operation — B6 is practically identical — and not mainly in maintenance and replacement. The decisive counterweight is the modelled end of life. [R01]

For the timber–straw variant, C3+C4 account for 49.10 tonnes CO₂e; for the massive variant, 9.18 tonnes. This alone reduces the gap by 39.91 tonnes. The somewhat higher maintenance and replacement emissions of the massive variant add 1.58 tonnes back. Thus 83.24 tonnes become 44.91 tonnes. [R01]

With biogenic materials, this is part of the accounting logic: carbon is taken from the atmosphere during plant growth, stored in the product and, in the standard end-of-life model, released again later. The current straw EPD documents this relationship for A1–A3 and C3. [Q18]

This makes the time question concrete. A large part of the difference caused by today’s material and construction choice is offset in the single score by an assumed release at the end of life — for a building constructed today, by a scenario for a world decades away.

What do we need to see today?

The hardest and immediately available core is A1–A3. By the time a building product reaches the site, these emissions — and the accounted biogenic uptake — are already linked to today’s product choice. No new LCA method is needed to see them; the information already exists.

The physical building decision does not stop at the factory gate. A4 transport and A5 construction are also triggered directly by the project. The intuitive boundary is therefore A1–A5: up to the point at which the building stands. Sweden has shown since 2022 that this scope can be handled in practice through its mandatory climate declaration, using simplifications, generic data, default values and project data where available. [Q15] A1–A3 can be the simplest robust starting point; A4–A5 can follow with pragmatic data collection. A method for climate protection now must also be usable now.

This separation is not an exotic bauwen idea. During preparation of the French RE2020, a separate A1–A5 indicator was discussed explicitly for lower uncertainty and for reducing emissions occurring “dès aujourd’hui” — from today onward. France later chose a dynamic life-cycle method. [Q17] Sweden is taking another route: Boverket proposes reporting life-cycle GWP while also setting separate A1–A5 limits from 2030. [Q16]

Make today’s effect visible

That gives us a workable next step. Keep the LCA over the entire life cycle. Alongside it, make the emissions triggered now — and the biogenic carbon stored now — visible as their own decision information.

The aim is a competition for lower present emissions and for as much sensible biogenic carbon storage as possible. That is exactly the direction we need. The next methodological step is to check the strongest side effects and resource constraints instead of delaying the first improvement until a perfect final method exists.

For wood, that means asking whether simply adding more material for storage remains resource-efficient in view of limited and competing uses. Straw is a different case. As an agricultural by-product used as insulation, it appears possible to increase material use very substantially before comparable resource conflicts become decisive. That is a working claim to be examined separately; a future FIND OUT article will look specifically at straw’s resource potential, side effects and storage effect as a biogenic insulation material.

So the method can improve step by step: make present effects visible, make storage visible, check obvious side effects with a few robust guardrails — and then improve again.

And then: limits

The Danish Reduction Roadmap makes a major move at exactly this point: it derives a building-sector reduction pathway from the remaining global CO₂ budget rather than from what is currently common practice. [Q20] That budget orientation is a fundamental achievement.

Its current official method still expresses the building target as an aggregated life-cycle value. After what we have just found about timing and modelled end-of-life effects, one question therefore becomes unavoidable: can that one life-cycle number really be the lead indicator for a building decision taken today — or should the budget-derived target be connected more directly to the emissions and storage effects that this decision triggers now?

Do not wait to start perfectly. Start better. Now.