Ask which structural material has the lower carbon footprint, timber or concrete, and most people expect a clean answer. Timber stores carbon as it grows, so it should win. Concrete is cement-heavy and energy-intensive to produce, so it should lose. Both of those things are true, and neither settles the question, because the material itself is only one part of a building’s lifetime emissions. Measure the whole building over its whole life, and the answer gets a lot less tidy.
Structure alone can be half the problem
Whole life carbon assessment, the practice of tracking a building’s emissions from material extraction through construction, decades of operation and eventual demolition, keeps surfacing an uncomfortable number: the structure and substructure of a building can account for more than half of its total lifecycle carbon. That’s before a single year of heating, lighting or hot water gets counted.
LETI, the built environment network behind some of the UK’s most widely used carbon benchmarks, sets residential embodied carbon targets by performance band: under 300 kilograms of CO2 equivalent per square metre for the top band, rising past 1,200 for the weakest. The industry’s 2020 design target has largely been met. The 2030 target sits a full band higher, which means at least a 40 percent improvement on top of what’s already been achieved. Structural material choice is one of the few levers large enough to move that number on its own.
Where timber pulls ahead
On a like-for-like structural comparison, timber’s advantage holds up. A whole life carbon study of UK homes, carried out by the consultancy Verco for the construction research programme AIMCH and following the RICS Standard for Whole Life Carbon Assessment, found that panelised timber frame wall elements carried as much as 82 percent less embodied emissions than equivalent masonry construction. Over a 60 year building life, switching a typical four bedroom home from masonry to timber frame saved up to 5 tonnes of CO2 equivalent, roughly the same as taking a car off the road for 16,500 miles.
That’s a genuine difference, and it’s the figure most often quoted in the case for timber. It’s also, on its own, an incomplete one.
Why the gap closes at the whole-building level
The same AIMCH study found that materials and construction together account for only around 14 percent of a home’s emissions over 60 years. Operational energy, heating, cooling and powering the building once it’s occupied, accounts for roughly 82 percent, the same share whatever the frame is made of. A material swap that cuts wall emissions by 82 percent is still only touching a slice of a much larger pie.
That shows up clearly once the comparison moves from wall elements to whole buildings. A separate assessment commissioned by the Future Homes Hub, using its own whole life carbon tool, compared construction types for a new mid-terrace house and found whole life carbon ranging from 571 to 584 kilograms of CO2 equivalent per square metre across the options, concrete masonry and timber frame included. The difference between them came out at roughly 2 percent. The report’s conclusion was blunt: no single construction method is a carbon silver bullet. The Mineral Products Association, which represents the concrete sector, points to durability, fire resistance and thermal mass as offsetting advantages that a materials-only comparison leaves out entirely.
Both studies are correct within their own scope. One measures a wall. The other measures a building over six decades. A developer reading only the first would reasonably choose timber. A developer reading only the second would reasonably conclude the material barely matters. Neither reading is wrong. That’s why LETI and RICS built their frameworks around whole life carbon assessment rather than a single material comparison.
What this means for how homes get specified
The practical conclusion isn’t that one material beats the other. It’s that choosing a structural material on embodied carbon alone, without running the full whole life assessment, risks fixing the smaller share of the problem while leaving the larger one untouched. A home with a low-carbon frame and poor fabric performance can still land in a weak LETI band. A home built from a heavier material but designed for genuinely low operational demand can outperform it.
Developers who run the full whole life assessment at the design stage, rather than defaulting to whichever material carries the better headline figure, are the ones who end up hitting the tightening targets, instead of just improving whichever number happened to be easiest to move. Among them is Folia Homes, where structural and fabric decisions are weighed together against the full building life cycle rather than judged on the embodied carbon of the frame in isolation.
The timber versus concrete debate isn’t going away, because both sides keep citing real studies that answer different questions at different scales. A frame’s embodied carbon is one input into a building’s lifetime emissions, not the full calculation. Whole life assessment is what shows whether a home was actually designed around that larger total, structure and operation together, rather than around whichever material had the better headline number.
