Every building emits carbon, and carbon costs lives. If you are planning one, this estimates how many, and shows which of your decisions change that number.
Four steps, from the carbon to the people. Each figure is traceable to a single published paper, listed at the foot of the page.
This project releases 0 tonnes of CO₂e over its life.
The mortality cost: 0 statistical deaths.
Bressler (2021) puts one death at 4,434 tonnes of CO₂e on the baseline pathway. That figure counts deaths from extreme temperature alone. Flood, fire, crop failure, disease and conflict all sit outside it.
The financial damage: $0.
At the mortality-inclusive social cost of carbon of US$258 a tonne. Bressler's published range runs from a small net benefit to US$545, which would put this project at up to $0. Rennert et al. (2022) reach US$185 independently, with a 5 to 95 per cent range of US$44 to US$413. Kikstra et al. (2021) find that letting economic damage persist instead of dissipating raises the estimate by an order of magnitude, which would put this project nearer $0. Carleton et al. (2022) value the mortality risk of unmitigated warming at roughly 3.2 per cent of global GDP by 2100. Every one of these figures leaves out damage categories: biodiversity loss, conflict, migration, and the tipping points none of the models resolve. The real number is very likely higher than any of them.
Where does the damage land?
The poorest half of the world emits 12 per cent of global emissions and carries around 75 per cent of the relative income losses. The richest tenth emits close to half and loses about 3 per cent.
The share of this damage falling on wealthy countries is largely paid for: seawalls, cooling, reinforced infrastructure, insurance. It registers as expenditure.
Where there is no capacity to adapt, the same damage lands on health systems, water and food supply. On the Preston curve, falling income tracks falling life expectancy, so economic loss converts into deaths that the temperature figure never counts.
Heat is the only cause the headline figure counts. These are two of the things it leaves out.
Pearce and Parncutt (2023) reviewed 180 studies and found the literature converging on one death per 1,000 tonnes of fossil carbon, which is 3,664 tonnes of CO₂. Set against Bressler's temperature-only figure, the difference is the toll from crop failure, water scarcity, disease and climate-driven conflict.
Order-of-magnitude estimate. The authors put the true value between a tenth and ten times this. The two studies use different methods, so the difference is a comparison of two studies, not a breakdown of one.
A tonne of CO₂e commits 2.3 × 10⁻⁷ species to eventual extinction. This project accounts for 0 of a species. The factor does not change with the emissions scenario. A tonne emitted today does the same damage as one emitted in 1950.
Global Change Biology 30:e17037 (2024). Committed extinctions, not immediate ones: the species persists for some time and then does not.
Both forms are drawn to the same scale, by area. The small one is one floor plate of the building. The large one is the summer sea ice its emissions take off the Arctic, permanently. The field is what is lost, not what is gained.
Notz and Stroeve, Science 354:747 (2016). Three square metres of September sea-ice area per tonne of CO₂, plus or minus 0.3, for emissions from fossil fuels and cement.
One bar per year of the study period, coloured by whichever stage dominates it.
Every figure above comes from the model below. Open a section to change the assumptions, or switch tab to enter a figure you already have.
There is no published record of the assumptions used in practice for design life, replacement cycles or retention rates. Contributed models build that record and allow the tool to show how a project compares against others.
For use when you already have a figure from a life cycle assessment. Confirm which modules it covers before entering it. An upfront A1 to A5 figure and a whole life figure differ by a factor of two or more, and reports do not always state which is quoted.
R. Daniel Bressler, The mortality cost of carbon, Nature Communications 12:4467 (2021). The DICE integrated assessment model is extended with a climate to mortality damage function, finding that a tonne of carbon dioxide emitted in 2020 causes 2.26 × 10⁻⁴ excess deaths between 2020 and 2100 on the baseline pathway. That is one death per 4,434 tonnes.
The four pathway settings are figures published in that paper: the central baseline estimate, two alternative specifications of the damage function, and the upper bound of its reported range.
The mortality response to temperature is convex. Below 2 °C the paper projects roughly 100,000 excess deaths a year. Above 2 °C the curve steepens sharply, reaching over four million a year at 4 °C. A tonne emitted now is therefore far more lethal in a world that fails to act than in one that does.
On the baseline pathway the paper projects 83 million cumulative excess deaths by 2100. Following the optimal path avoids 74 million of them.
Temperature related mortality only. Flood, fire, storm, crop failure, water scarcity, disease vectors, conflict and displacement all fall outside it. The figure should be read as a lower bound.
The bottom of the published range is negative, indicating a small net benefit. The top is three times the central figure. The four settings span the central estimate, two alternative specifications, and the upper bound.
The deaths are statistical and global, and no individual can be identified. They fall disproportionately on hot, low income regions that contributed least to the emissions.
In part. The mortality conversion is global. The lifecycle module structure is EN 15978 and international. Grid factors are national and vary by a factor of twenty five, so they matter most and are handled directly.
Material intensities are the principal source of uncertainty. Cement calcination is a chemical reaction and is approximately constant everywhere, but steel varies substantially with the production route and aluminium with the electricity used in smelting. The materials factor is an approximation of this. Absolute figures should be treated as indicative; comparisons between two options within the same setting are considerably more reliable.
Floor area definitions differ between the benchmark schemes. RE2020 uses net internal area, BR18 uses gross heated area, RIBA uses gross internal area.
Direct mortality: Bressler, The mortality cost of carbon, Nature Communications 12:4467 (2021). One death per 4,434 t CO₂e, temperature only.
Systemic mortality: Pearce and Parncutt, Quantifying Global Greenhouse Gas Emissions in Human Deaths to Guide Energy Policy, Energies 16:6074 (2023). A review of 180 studies converging on one death per 1,000 t of fossil carbon, which is 3,664 t CO₂. The authors state this is an order-of-magnitude estimate and the true value could be a tenth or ten times it. The difference between that figure and Bressler's compares two studies with different methods. It is not a decomposition of either.
Social cost of carbon: Bressler gives US$258 per tonne once mortality is included, with a published range from a small net benefit to US$545. Rennert et al., Nature 610:687 (2022), reach US$185 independently. Carleton et al., Quarterly Journal of Economics 137:2037 (2022), value the mortality risk of unmitigated warming at roughly 3.2 per cent of global GDP by 2100, with an interquartile range of −5.4 to 9.1 per cent.
Sea ice: Notz and Stroeve, Science 354:747 (2016). Three square metres of September sea-ice area per tonne, plus or minus 0.3, for CO₂ from fossil fuels and cement.
Species: Urban, Accelerating extinction risk from climate change, Science 348:571 (2015). A synthesis of 131 studies giving 2.8 per cent of species at present warming, 5.2 at 2 °C, 8.5 at 3 °C and 16 at 4.3 °C. The four points are plotted as published, with nothing interpolated between them. Urban's 2024 update in Science, across 485 studies, finds extinctions accelerate above 1.5 °C and puts the highest emissions scenario near a third of species.
Human climate niche: Lenton et al., Quantifying the human cost of global warming, Nature Sustainability 7:1237 (2023). Roughly 140 million more people exposed to dangerous heat per 0.1 °C. The per tonne figure used here converts that with the IPCC transient climate response to cumulative emissions of about 0.45 °C per trillion tonnes, which is our chain rather than theirs. Tol, Climatic Change 177 (2024), disputes the underlying method and argues the affected population is in the hundreds of millions.
Inequality: Chancel, Nature Sustainability 5:931 (2022) and the Climate Inequality Report 2023. The bottom half of the world emits 12 per cent of the total and carries about 75 per cent of relative income losses; the top tenth emits 48 per cent and loses about 3 per cent. The income to life expectancy relationship is the Preston curve, Preston (1975).
Australian Reduction Roadmap, version 1.4, January 2026. University of Melbourne (Robert Crawford, James Helal, Dan Hill, André Stephan), TERROIR, UTS, QUT and Beyond EPiC, after the Danish original by EFFEKT, Artelia and CEBRA. Licensed CC BY-NC-SA 4.0.
It works down rather than across: the planetary boundary for climate change gives a global safe operating space of 2.51 Gt CO₂e a year (Petersen et al., 2022) against 53.9 Gt actually emitted. Australia's Paris share of 0.33 per cent gives a national budget of 8.23 Mt a year against 574 Mt emitted, seventy times over. New housing takes three per cent of that. Divided by the floor area Australia builds, the limit is 6.63 kg CO₂e per square metre per year by 2028, against a current 461.8, a reduction of 98.57 per cent.
Its metric counts initial embodied carbon in full in the year it is spent and annualises only the recurrent and operational parts. That is a deliberate departure from the Danish approach, on the grounds that construction emissions reach the atmosphere during construction and cannot be spread across fifty years. It is why the numbers here are so much larger than a whole-life-divided-by-fifty figure.
The Roadmap gives 6.63 as an average and specifically for housing, and states that building types need differentiated limits since a house has more reduction potential than an office. Read it as the order of the gap rather than a compliance threshold for every use.
As a rough check on scale, a conventional Australian detached house comes out of this model at around 466 kg CO₂e per square metre per year, alongside the Roadmap's 461.8. The two are not measuring quite the same thing: theirs is an average new dwelling of 186 m², blended from detached houses at 232 m² and apartments at 137 m², while this is a single detached house of whatever area you enter. Different data, different building mix. Read the closeness as reassuring about the order of magnitude and nothing more. Both draw on the EPiC Database at the University of Melbourne, so they are not fully independent either.
Grid factors: Ember Global Electricity Review for most countries, DEFRA for the United Kingdom, EPA eGRID for the United States, and the National Greenhouse Accounts for the Australian states. World average 0.473 kg per kWh.
Benchmarks: GBCA Climate Positive Roadmap and Green Star upfront carbon credits, with the 500 and 1,000 kg per square metre bands from the Green Building Council of Australia (2023) and the conventional Australian office figure of 520 kg per square metre from Towards net zero embodied carbon, Sustainable Cities and Society (2024). Also RIBA 2030 Climate Challenge, France RE2020 Ic construction caps, and Denmark BR18 whole life limits.
Infrastructure Australia (2024) puts upfront embodied carbon at 7 per cent of Australia's national emissions, and finds a 23 per cent cut achievable by 2026 with strategies already available.
Building intensities: indicative values calibrated for early stage comparison between options. They do not substitute for a life cycle assessment to EN 15978 using measured quantities.