Meme Weeding: Embodied Carbon
The greenhouse gases emitted by the production of concrete, called embodied carbon, are occasionally used as a green-NIMBY argument against building new things. A Berlin Green spokesperson coauthored a study opposing U-Bahn construction on the grounds that the concrete used in construction would raise emissions. More recently, I’ve seen American opponents of transit-oriented development in Manhattan, of all places, talk about the high embodied carbon of new high-rise buildings. Katja Diehl calls for a moratorium on new buildings on anti-concrete grounds, and a petition for the EU to shift regulations to be against new buildings and in favor of reuse on embodied carbon grounds got written up favorably by Kate Wagner in the Nation. Against all of this, I’ve found some numbers on the actual emissions involved in concrete production for new buildings, and they are so low as to be insignificant, 1.5 orders of magnitude less than transportation emissions. A decarbonization strategy should largely ignore embodied carbon concerns and embrace pro-growth sentiments: big buildings, big subway systems, big cities.
What is embodied carbon?
Embodied (sometimes called embedded) carbon is the carbon content emitted by the production of materials. The production of concrete emits greenhouses gases, mainly through two mechanisms: the chemical process used to produce cement emits CO2 by itself, and the energy used for production adds to the emissions of the electric grid.
What are the embodied carbon emissions of new buildings?
The embodied carbon content of concrete depends heavily on the local electricity grid as well as on the required strength of the material, with stronger requirements leading to higher emissions. The Climate Group commissioned a report on this in the British context, finding a wide range, but the average is around 250 kg of CO2-equivalent per m^3 of concrete, the 75th percentile is about 300, and the upper bound is 450. This is a cradle-to-gate figure, taking into account the existing conditions of the carbon intensivity of where concrete is produced and of the logistics system for getting it to the construction site. This is already with some reductions from a previous baseline (EC100; the UK average is around EC60), and further reductions are possible, through decarbonizing the logistics and production; the goal of the report is not to bury the concept of embodied carbon as I do but to propose ways to reduce construction industry emissions.
The question is now how to convert cubic meters of concrete into square meters of built-up area. I have not seen European figures for this, but I did find a 2012 report by the Building and Construction Authority. In Singapore, the sustainability index used is the concrete usage index (CUI), measured in meters (cubic meters per square meter). The example projects given in the study, all around 15 years old, have a CUI of 0.4-0.5 m, and it was pointed out to me on social media that in Toronto the average is 0.55 m.
250 kg/m^3 times 0.4 m equals 0.1 t-CO2 per m^2 of built-up area. A 100 m^2 apartment thus has an embodied carbon content of around 10 t-CO2. This is relative to a baseline in which there is already some concern for reducing construction emissions, both the CUI and the carbon content of concrete per m^3, but this is largely without techniques like mass timber or infra-lightweight concrete (ILC). In Singapore the techniques highlighted in the BCA report are fully compatible with the city’s high-rise character, and the example building with gold but not platinum certification has 25 stories.
Should we worry about construction emissions?
No.
An aggressively YIMBY construction schedule, say with 10 dwellings built annually per 1,000 people, say averaging 100 m^2, emits around 0.1 t/capita annually: 0.1 t/m^2 * 100 m^2/unit * 0.01 unit/capita. All figures have ranges (and if anything, 100 is high for the places that build this much urban infill housing), but factor-of-1.5 ranges don’t erase an order of magnitude analysis. The emissions produced by construction, even if it were raised to some of the highest per capita rates found in the developed world – in fact higher rates than any national average I know of – would be about two orders of magnitude lower than present-day first-world emissions. They’d be 1.5 orders of magnitude lower than transportation emissions; in Germany, transport is 22% of national emissions and rising, as all other sources are in decline whereas transport is flat.
There’s a lot of confusion about this because some studies talk about buildings in general providing a high share of emissions. The Bloomberg-era PlaNYC spoke of buildings as the top source of emissions in New York, and likewise the Nation cites WeForum saying buildings are 37% of global emissions, citing a UN report that includes buildings’ operating emissions (its topline figure is 10 Gt in operating emissions, which is 27% of global emissions in 2022). But the construction emissions are insignificantly low. This means that aggressive replacement of older buildings by newer, more energy-efficient ones is an unmixed blessing, exactly the opposite of the conclusion of the green movement.
Instead of worrying about a source of emissions measured per capita in the tens of kilograms per year rather than in the tons, environmental advocates need to prioritize the most important source of greenhouse gases. The largest in developed countries is transportation, with electricity production usually coming second, always falling over the years while transport remains flat. In cold countries, heating is a significant source of emissions as well, to be reduced through building large, energy-efficient apartment buildings and through heat pump installation.
Regulations on new construction’s embodied carbon are likely a net negative for the environment. The most significant social policy concerning housing as far as environmental impact is concerned is to encourage people to live in urban apartment buildings near train stations. Any regulation that makes this harder – for example, making demolitions of small buildings to make room for big ones harder, or demanding that new buildings meet embodied carbon standards – makes this goal harder. This can be understandable occasionally if the goal of the regulation is not environmental, for example labor regulations for construction workers. It is not understandable if the goal is environmental, as the concern over embodied carbon is. People are entitled to their opinion that small is beautiful as a matter of aesthetic judgment, but they are not entitled to alternative facts that small is environmentally friendly.
Pedestrian Observations 
Any person interested in using this to harass either Katja or Kate on social media is welcome to delete their account instead. Go start flamewars over the Israeli-Palestinian conflict or relitigating the 2016 Democratic primary or something (not here).
The [report](https://www.unep.org/resources/publication/2022-global-status-report-buildings-and-construction) gives 3.6 Gt for emissions “from producing buildings materials of around (i.e. concrete, steel, aluminium, glass, and bricks).” So that’s still about 10% of 2021 global emissions. It’s obviously less than 37%, but is it “insignificantly low”?
Concrete and steel are together 5%. The industrial emissions of steel are mostly not about the construction of new residential buildings but construction of other things, like industrial buildings or infrastructure; I can’t find great sources on steel consumption for residential buildings, but I’m seeing 42 kg/m^2 in one example (another giving 65 is an almost all-steel building with little concrete), a range of 20-40 in a Pakistani industry source, a figure in a Ukrainian consultancy that is ambiguous on whether it’s 21 t/480 m^2 (43.75 kg/m^2) or 21 t/4,320 m^2 (4.86 kg/m^2). The CO2 intensity of steel production is a bit less than 2 t CO2-e/1 t steel globally (link), and is 1.57 t/t in Germany (link). So we’re likely talking about somewhat less than doubling the embodied carbon when including steel, going from around 0.1 t/m^2 to 0.16-0.18 t/m^2.
High-rises in Singapore are said here to have 135-138 kg/m^2, giving 0.18 t-CO2e/m^2 (the paper uses lower steel emissions), but then the same paper thinks the emissions intensity of concrete is 0.236 kg/kg rather than 0.25 t/m^3 (which is around 0.11 kg/kg). With these higher factors one gets to around 0.44 t/m^2, which makes it a secondary but significant source of consumption emissions rather than an insignificant one as in Germany, in the context of a society with 56% public transport modal split and 30% household car ownership.
Darn, it’s unfortunate Kate Wagner is choosing to focus on this. I credit her as my humorous gateway (McMansionHell) to critically examining home build quality, which in a very roundabout way led me to Crabgrass Frontier by Kenneth T. Jackson.
But it’s not surprising, I suppose. She is an architecture enthusiast and inclined toward preservation. And having both come of age and become famous on social media, where hivemind narratives that skew toward dunking on opponents rather than solving problems dominate the conversation, she has now chosen to focus on an easy villain: those greedy developers.
What is surprising, however, is that she has written favorably about brutalist architecture in the past. Brutalism isn’t brutalism without reinforced concrete.
(I hate brutalism and I hate Le Corbusier. Well, I take that back, I like DC Metro stations.)
I think it speaks to the architect that so many brutalist haters, myself included, exempt the DC Metro. It’s hard to think of other examples of a ‘piece’ that both haters and fans of the ‘genre’ overwhelmingly like. Maybe a couple songs, but even that’s less extreme imo.
Ha, no kidding. I think I respect the commitment to a common design. Go big or go home. I went to college in the area and commuted across town for a summer internship, so I have fond memories; I also use it when I visit nowadays because driving and parking in DC is stressful. The indirect lighting in side-platform stations is a soothing feature, and the air conditioning is a massive relief from the hot, humid DC summers.
One disadvantage which I saw more of in a recent visit earlier this year is water damage. A number of the tunnel linings in Red Line stations are showing visible, ugly discoloration and cracking. This is something you can’t escape with reinforced concrete. It stains and is difficult to repair.
As far as a piece that haters and fans of the genre overwhelmingly like, I’d float the structure vault at Washington Union Station. It’s beautiful. But I’m a hater of pretty much everything else about WAS. Through-platform separation from the waiting area; the waiting area itself; low level boarding and debarking for NEC through trains (why are there even NEC through trains without VA electrification? Why doesn’t Amtrak just make passengers to points south transfer? Who is going from NJ to Richmond or Norfolk?); the rental car facilities and garage; I could go on.
One could argue that the DC Metro really isn’t brutalist. Yes the vault is made of concrete, it the shape and the coffers were specifically chosen to evoke architectural elements prevalent in the city’s Greco-Roman public buildings (domes and colonnades, respectively). [The coffees also perform a structural function, but that just highlights Harry Weese’s genius in combining form and function, as great architects do]. Bare concrete (“beton brut”) is not the key element, the shapes are, which is inherently an un-brutalist approach. Furthermore, the platform floors are red tile and the key element of the signage and particularly above ground entrance are the smooth black pillars; neither at all brutalist.
I think fans of brutalism reveal themselves and the bankruptcy of the genre when they try to claim the DC Metro as an example of brutalism: not only is it not particularly brutalist a la Corbusier and others, but picking an example that it literally out of sight underground isn’t exactly an inspiring choice for the promoting how buildings should look. But it is fantastic architecture and you can see concrete so brutalists try to use it to argue their form can look good too.
Bare concrete has been around a long time. . .
https://en.wikipedia.org/wiki/Pantheon,_Rome
…. it’s even got coffers.
Very interesting points! I decided to look up what architects think. And I found something interesting there too!
In 2014 the American Institute of Architects bestowed their 25 Year Award on the Metro for recognizing architectural design of enduring significance. And in the award notes it does not use the word Brutalist or Brutalism once! The closest it comes is describing the curvilinear mezzanine platform with the fare gates as “Corbusian,” which is not a universal design feature.
Instead Metro stations are described as “[combining] Modernist forms with subtly classical elements to create an experience that speaks to the contemporary power and complexity of the federal government…”
I would agree with that, even in this period of dramatic corruption and instability. So there you have it – you are correct, and even professional architects don’t describe Metro as brutalist.
Back to hating Corbusier!
“One could argue that the DC Metro really isn’t brutalist.”
One could argue this, I suppose. It’s not a good argument.
“Bare concrete (“beton brut”) is not the key element, the shapes are, which is inherently an un-brutalist approach. Furthermore, the platform floors are red tile and the key element of the signage and particularly above ground entrance are the smooth black pillars; neither at all brutalist.”
The raw concrete is absolutely THE KEY element in all the classic Harry Weese Metro stations; likewise, there’s nothing about Brutalism that is against these kinds of forms – the whole movement was about what the possibilities of concrete can unlock. Similarly, there’s no requirement that every single material be concrete. The idea that the terra cotta floor tiles somehow mean the stations aren’t brutalist is absurd.
Looks like it was inspired by the Pantheon to me….
The raw concrete is absolutely THE KEY element
No the arch and coffers are the key elements. If you look at the buildings most frequently cited as typical of brutalism (i.e. Boston City Hall, Habitat 67, Unite de Habitation, Royal National Theatre) the thing that jumps out as most conspicuously absent are curves, as well as surface ornamentation breaking up flat surfaces. Yet those two items are exactly what define Weese’s metro stations. This is no accident, the design is universally acknowledged as having been inspired by the neoclassical architecture that so defines DC’s major public structures. I could see placing DC metro in the modernist category (it’s not like those arched stations have Doric columns along the wall with painted and gilded ceilings) but it is not brutalist.
If including tile on the floor doesn’t mean its not brutalist (a bit of a contradiction with your opening statement) then the use of concrete does not mean it IS brutalist.
As an aside, Habitat 67 is the only Brutalist building I can see that has any aesthetic appeal or interest. It at least makes unique and interesting use of the principles of linear/blocky forms, with the large scale form of the structure providing visual cues, allowing the flat and plain walls to recede into the background (the reverse of many – but not all – traditional styles where the shape is often a simple box but the detailed appearance of wall materials, windows and decorations provides the engagement). With every other brutalist building the abstract forms (search for “Leon Krier gravity check”) combined with vast expanses of totally bare walls produce a soul crushing experience.
She is a leftist. However, as someone who also identifies as a leftist, it’s frustrating to see anti-developmentalism seep into so many nooks and crannies of our side. If you start from a base of “human life is inherently or can be made good, ergo ceteris paribus more human lives is better”, you have an obligation to build the world such that it can support as many people as possible (I don’t go the repugnant-conclusion step of “the maximum number of people–however barely happy they are in net–is the morally-obligatory number”).
There are very obviously problems with the way development occurred during the 20th century, but seeing that and concluding “all development is bad” is a mistake. Not one I’m accusing Kate Wagner of making, per se, but definitely one that a lot of leftists make. They often then fail recognize that the idea of the world as the zero-sum place it would be–was–without development is to see the world as a much worse place, for fewer people, and that accepting a zero-sum world as a truism legitimates a lot of the nasty things a lot of people on the right are fine with having happen, as long as it doesn’t happen to them.
She’s also explicitly not a NIMBY, unless one counts “finds Matt Yglesias annoying” as NIMBYism, in which case everyone on the Internet including Slow Boring subscribers is a NIMBY; notably, she’s always been positive on single-stair reforms in the US, which is more than I can say for a lot of American left-leaners who find the idea of reducing a regulation inherently repulsive.
Well, considering what reducing regulations has often meant in the past, I can understand the reflex. Nonetheless, in my very contrived, narrow, particular sense of what “leftist” means, we have a responsibility to look at the facts of the world, not our ideas about it, and amend our ideas to those facts.
Yes, “facts” which are “objective” is difficult, but not impossible. Prima facie, I don’t think of European cities as being ones where people routinely die trapped in apartment fires, so more closely examining US apartment regs to see how functional they are is reasonable in the purest sense.
Just how much money do the landlords get to save and how many dead apartment dwellers is an acceptable level?
It is really hard to compare countries usefully. There are many confounding variables which means you cannot compare numbers and learn anything. US does of course have about double the fire death rate vs Europe, but both numbers are overall very small. I’m not sure about Europe, but in the US the newer the building the lower the fire death rate. The US in general builds with a lot more wood than Europe.
Every time I see someone speak on the subject they are doing shallow analysis on numbers, but a deep dive into all the variables is really needed. Of course a deep dive would take experts several years of work to isolate variables and result in a 1000+ page report that few people would read. I have no doubt it would result in useful recommendations on how codes could change to support various different construction styles. However without that report everyone should worry that their proposed change is actually worse (including those in Europe bragging about lower fire deaths – is their single staircase killing a lot of people needlessly and just appearing better because of something the US doesn’t do anymore?) Such a study would cost millions of dollars so I can’t fund it (I wouldn’t be surprised if it was already done, and buried in some academic journal where most of us don’t know how to find it – while those who could find it are not looking because it would not support their position)
No it wouldn’t. Insurance premiums aren’t calculated on a whim. The insurers have numbers so the underwriters can calculate a premium. All day, every day. And then they sell off their risk to other insurers and someone in Switzerland can tell you what the risks are in the U.S. or Australia. Governments also keep track of this, to assure the insurance companies aren’t gouging. Which is how you know
People dying in wooden single family houses that don’t have any stairs because it’s a single story house built on a concrete slab doesn’t tell you much about how survivable a tall buildings are.
The argument is used against railroad, nuclear plants, etc also
Yesterday, the World Bank ended its multi-decade ban on funding nuclear plants in developing countries. After the article announcing this, the second comment said (in summary) “nuclear plants use so much concrete that they are a net-energy loss over their lifetimes.”.
https://xkcd.com/1162/
Oh sweet Jesus, not this again.
Cue the Thorium Bros to Well Actually.
This is one of the reasons I quit Reddit. The karma hive mind loves nuclear power. Well, so do I, and in terms of energy density, yes, absolutely true; the world is unlikely to meet decarbonization targets without increasing the use of nuclear energy.
But there is zero nuance in the discussion on social media. No acknowledgments of costs or what drives them (regulatory issues and permitting to name just two), fuel refinement, spent fuel storage, or availability of fresh water sources. In fact it is almost guaranteed if you bring up spent fuel storage as an issue someone will respond with immature reprocessing technologies and get upvoted to the moon. I’m sure everyone here is familiar with Godwin’s Law or Reductio ad Hitlerum – you could write the same thing about fission power; call it Reductio ad Thorium.
And then there are the real sci-fi types who point to ITER or NIF as the silver bullets that will save us all. I’m in favor of dramatically increased investments in fusion power research, but the data suggests commercial viability will come too late at scale to bend the warming curve compared to adoption of renewables, let alone, uh, use in cool-looking spacecraft fighting beltalowda or bipedal war machines with sweet names like Timber Wolf and Kodiak.
I recall a Vox article titled “Why Nuclear is so much more expensive in the US than other countries” (or something similar enough) and the answer is basically other countries build more nuclear energy and allow professionals to handle the process, so they’re better at it than we are (e.g. France, South Korea)…sounds like a narrative familiar to readers of this blog!
The zero-nuance karma hive mind seemed to be just as much a factor at the the World Bank and others (Germany, Japan) who completely shut out nuclear power as a matter of first principle. Only the closed minds of those policy makers have had much more of an (negative) effect than internet fan boys, when you consider the CO2 per capital emissions of France vs. Germany.
I don’t care where my electricity comes from. Neither do you.
The data suggests it will never be commercially viable. The people predicting how fast prices of renewables and batteries will drop, keep getting it wrong. They fall faster. They also get it wrong when they predict how much will be installed. It’s more. The data suggests that the prices of renewables will be too low to do 20th century things like build central power stations. Sometime very soon. Using the flood control dams for hydroelectricity will continue to make sense. And that will likely be about it. Because I don’t care where my electricity comes from. Neither do you.
Depends on who is cooking the books which way. Even though they apparently do it quicker and cheaper that doesn’t make it cheaper than renewables and batteries. There is a plan to submerge high voltage DC lines from Morocco to the U.K. Cheaper than the fission power plants they are considering. That depends on who is cooking the books which way.
Because I don’t care where my electricity comes from. Neither do you. We do care about how much it costs. ….Recharging the batteries is getting too cheap.
Pro tip: when one encounters the word “nuance” or “nuanced” … just … stop reading, simply stop reading, right there. Move on. Such subtleties are not for the likes of you, thank God.
There are guaranteed better ways to spend the scant minutes of one’s life.
You’re welcome.
Works 99+%! (But but but, what about the nuanced reasoning of the 0.49% you callously discarded! Whatabout the deep both-sides arguments to which you are deaf? Whatabout them?)
* Japan is not shutting nuclear power, they are now progressively reopening nuclear plant closed after 2011 earthquake, and new construction plan are also formulating
Here’s a link to an article about making concrete more environmentally sustainable.
https://archive.li/e7Lkp
NIMBYs aren’t against new things. They want them to be someplace else. The people who don’t want to build anything are BANANAs – build absolutely nothing anywhere near anyone. Either of them will clutch at any excuse so they don’t have to tolerate any changes.
I’m assuming they used NIMBY and not BANANA because the former has more currency than the latter.
In far far upstate New York, the parts north of 96th Street. Where the central steam runs out. Way way south of the Staten Island ferry it can be cooling.
https://www.eia.gov/energyexplained/units-and-calculators/degree-days.php
Pick someplace in Hawaii and heating and cooling needs are much lower.
In your puritanical dictatorial dystopian fantasy. Abandoning existing buildings isn’t very efficient or “green”. Without coercion, people currently living in suburban splendor aren’t going to move into an apartment near work. Mostly because convincing someone to build the apartment will be difficult. It’s going to be difficult to buy an internal combustion automobile in the near future. Electric cars keep getting cheaper and cheaper. And when they are charged overnight with all the excess wind power, don’t have carbon emissions. Or with the PV over the parking space at their employer. Or both.
Heat pumps last 20, 25 years. Insulation is forever. Better insulation means you need a smaller heat pump which is cheaper to buy, cheaper to run and cheaper to replace. While the insulation is keeping you more comfortable. Which because it doesn’t have any moving parts, lasts forever. The insulation can be installed years before the heat pump. Which cuts carbon emissions now.
The only thing that’s less efficient than abandoning existing buildings is forcing immigrants to move to them to fill the housing in Scheissdorf, Thuringia that people have fled as soon as the Inner German Border was removed, and then there are no jobs in Scheissdorf and the media writes about how immigrants can’t find jobs and this proves integration has failed and they should all be deported.
(I am only slightly exaggerating.)
Tearing them down to return to nature, building apartment blocks hovering over the train station only to be abandoned would be less efficient. You aren’t going to stuff the automobile genie back in the bottle short of a puritanical dictatorship that lasts as long as the one in North Korea. Wide swaths of suburbia aren’t going to return to nature. They’ll slap PV on the roof, over the parking lots and erect windmills to keep the batteries charged. The dunkelflaute is less flaute if there are a lot of batteries and HVDC lines.
I’m not stuffing anything in a bottle, but there’s higher demand in the cities than in the towns here, and between 2002 and 2017 the Mobilität in Deutschland reports showed (slowly) rising public transport modal split at the expense of cars.
Silly me, I mistook
and linking to an article about housing in the U.S….. to be about something other than Germany.
The other main environmental argument used by NIMBYs in Germany to block development is Versiegelung (impervious surfaces). Although the obvious way to reduce it is to build tall and dense, the opponents of construction always implicitly assume that people who can’t find an apartment in the city will simply disappear.
I think this is a great article and is very interesting.
That said there are political advantages of reusing existing buildings where possible.
Maybe in Britain we should demolish the 1875-1925 on energy use grounds, but the newer stuff is certainly upgradable to something reasonable.
And even for the Victorian stuff if you do double glazing, loft insulation and possibly underfloor insulation and do an air-air heat pump powered by wind/solar is the energy usage really an issue.
This is like people who are worried about how much water the water bottling plant uses in a drought: they have absolutely no idea about proportionality. Buildings don’t use very much concrete. Freeways, bridges, aqueducts, dams, roads, and civil engineering projects in general use so much more concrete than buildings that it’s hardly worth considering the buildings.
I don’t know if you’ve listened to the Teurer Fahren podcast: https://detektor.fm/serien/teurer-fahren-teurer-wohnen
Overall it’s a pretty good investigative podcast on many of the issues with Deutsche Bahn and its infrastructure over the past 35 years. The topic of embodied carbon came up in [episode 5](https://detektor.fm/politik/teurer-fahren-episode-5-neubaustrecken-schienenfreunde-tunnel), as part of the question “does Germany build too many tunnels. They brought up some statistic of the embodied CO2 emissions of building one meter of tunnel and then made some nonsensical comparison (“same amount of CO2 as a car driving around the world twice” or something like that). It’s really just a pretty minor point in the larger story, but I think it shows how widespread this thinking is in Germany.
Driving around the world twice is “only” 80,000km. If we assume 1000 passengers per hour, and 16 hour days (not unreasonable numbers, though you can likely to higher on both) that is only 5000 days to break even on the tunnel – less than 14 years. In short by their own numbers tunnels for trains look very good.
To be honest, as a European reader from The Netherlands (a staunch fan of Pedestrian Observations) this is a very confusing blog to read. Let me try to give you my impressions.
First of all, it comes across as a very polarized debate. Can one not be both interested in Transport Oriented Development and low carbon construction? In my office we are currently working on a big project (big for Dutch standards, the tallest building is 100 m high) that is right next door of a major intercity train station, but that is at the same time roughly Paris Proof in terms of embodied carbon. It is also net zero. And it replaces a few existing low rise buildings (partly recycling them). Of course, if you are interested in reducing carbon footprint you should take the urban typology (where are we building, how, in what density, how do you get there, what infrastructure is available) into account. A lot of research is done by urban planning offices on this topic, including by my office.
Secondly, I think you refer to the HouseEurope! petition. You call it “a petition for the EU to shift regulations to be against new buildings and in favor of reuse on embodied carbon grounds”. To my mind it is more nuanced than that. The movement aims to stop a system that is built on (blind) financial speculation. It’s about much more than CO2 only: “While development is essential for our society, it’s equally crucial to ensure that it doesn’t come at the expense of existing communities, local economies, our planetary ecosystem, and history”. Often, large (concrete) buildings from the 60s, 70s and 80s are demolished whereas they are great for reuse, be it by stripping it down to the structure and consequently redevelop it, building another couple of stories in timber on top of it, or simply by converting it to another function (i.e. offices that become housing). It costs a bit more imagination to begin with, but I can show you many successful projects that were realized in the last 10 to 20 years, resulting in an urban fabric that is much more interesting and vibrant than any tabula rasa approach can ever get. I also did sign that petition. But hey, sometimes, after careful consideration, you indeed better demolish a building…
Thirdly, you suggest that there is little research done on the actual numbers. At least in Europe, that is not the case. With each building permit, in many countries, one is obliged by law to hand in the actual embodied carbon number in kgCO2/m2 and this is based on solid calculations. (For this reason I could give you many many examples and much more data, but for the sake of brevity I won’t). And this brings me to the metrics involved. 250 is a good average GWPa for concrete per m3 (though circular concrete in The Netherlands currently has a GWPa of only about 57/m3) but a building is more than just concrete. Steel has a high impact too. 0.1 T per 1 m2 of build up area is, we believe, a very low number. From our own studies, we have seen that a sprawl typology has about 750 kg CO2/m2, a block typology has about 400 kgCO2/m2 and a highrise has about 1160 kgCO2/m2. (And yes! Roads and utilities are not yet included in these numbers. CO2 emissions due to required infrastructure are expected to be about 4 times lower in the case of a block typology than in the case of detached and semi-detached housing.)
Based on the data we have, the Cement industry accounts for 8% of total Global GHG emissions. We would not call that insignificant. Are there more important issues than that? Surely yes. But should we for that reason disregard the emissions of the cement industry altogether?
Kind greetings from The Netherlands,
Maarten Lever
“disregard the emissions of the cement industry altogether?”
Well, possibly! Alon is not saying that there are no emissions from cement. But you cannot consider those emissions in a vacuum. Regulations that burden new construction result in less new construction and/or costlier new construction. You have to compare that to the status quo: where are the people who would live in the new construction now living? What is their annual GHG contribution based on lifestyle? In other words, if new development enables people to move from car-centric suburban/exurban settings—or even an urban setting but one w/o easy access to non-car transit—then that new development is far more valuable! Of course, you’d need good modeling to find precise points of intersection and inflection, but you haven’t provided data that directly challenges Alon’s thesis. You have to show that these concerns about new construction’s GHG emissions outweigh the status quo. It seems that your perspective only compares the GHG emissions of new construction to the emissions of not constructing the building, which is incomplete.